Symposium II: Ion Beams---New Applications from Mesoscale to Nanoscale

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SYMPOSIUM II

II: Ion Beams---
New Applications from
Mesoscale to Nanoscale

April 26 - 29, 2011

Chairs
 

Giovanni Marletta
Dipto. di Scienze Chimiche
Universita degli Studi di Catania
Viale A. Doria 6
Catania, I-95125 Italy
39-095-7385130

       

Ahmet Oztarhan
Engineering Dept.
Ege University
Bornova, Izmir, 35100 Turkey
90-232-388-0378 x-145

John Baglin
K10/D1
IBM Almaden Research Center
650 Harry Rd.
San Jose, CA 95120
408-927-2280

       

Daryush Ila
Center for Irradiation of Materials
Alabama A&M University
Huntsville, AL 35762-1447
256-372-5867

Symposium Support
NASA
National Electrostatics Corporation


Proceedings to be published in both print and electronic formats
(see MRS Online Proceedings Library at www.mrs.org/opl)
as volume 1354
of the Materials Research Society
Symposium Proceedings Series.
 




* Invited paper

 

SESSION II1: Bio Materials and Applications
Chair: Daryush ILA

Tuesday Morning, April 26, 2011
Room 3016 (Moscone West)


8:00 AM *II1.1
New Directions of the Ion Beam application for Bio-modification. Robert L. Zimmerman1, Emel Sokullu Urkac2, Ahmet Oztarhan2 and Daryush Ila1; 1Physics, Alabama A&M University, Huntsville, Alabama; 2Bioengineering, Ege University, Izmir, Turkey.

Only relatively recently have high energy ion beams been used to modify and improve materials for applications in medicine and biology. Our team has been among a few other pioneer research groups in the ion beam community who have studied the interaction of an MeV ion in its track through many biocompatible materials in order to tailor their properties for medical applications, control cell adhesion, improved surface properties of polymers used for heart-valve, for hip-joint implants, for fabrication of nano pores, as well as to change the surface properties of bio-compatible polymers for controlled drug/medication delivery. We present here a review of the fundamentals of ion interactions with materials, particularly polymers, and describe three examples among many studies of ion beam modified biocompatible materials completed, or underway, at the Center for Irradiation of Materials of AAMU. The permeability of glassy polymeric carbon (GPC) varies with heat treatment temperature during preparation, and with the energy and specie of ion bombardment. By percolating a molten lithium salt into the pores of GPC and using a proton ion beam Nuclear Analysis Technique (NRA), we extensively studied GPC permeability and how to control it. Thus, the elution rate of lithium out of GPC into a physiologic solution can be controlled. GPC is a candidate for designing lithium drug delivery systems. With our molding and spraying techniques we can make layered samples with drug concentration gradients appropriate to a specified time delivery of drugs other than lithium. Producing structures in membranes at the nanometer scale can serve several applications, such as to localize molecular electrical junctions and switches, to function as masks, and for DNA sequencing. We have demonstrated the fabrication of nano scale pores in fluoropolymer films using scanned ion beam bombardment. The process has advantages over chemical and etching processes. The pores were produced using a feedback controlled gold ion beam system and were analyzed using optical and atomic force microscopic (AFM) analyses. We have succeeded in enhancing the properties of the GPC used for the moving parts of carbon replacement human heart valves by MeV ion implantation of silver. Potentially dangerous accumulation of natural cells attached to the valve after installation has been eliminated. A small amount of silver imbedded below the surface of the parts of a carbon heart valve exposed to the blood flow completely inhibits cell growth. By steering the MeV silver ions appropriately patterns are made such that normal cell attachment occurs within 100 microns of silver implanted areas. Although the total amount of silver is not toxic, we have shown that the leach rate is so low that the cell inhibition properties of a heart valve will not diminish in vivo.


8:30 AM *II1.2
Universal Biomolecule Binding Interlayers Created by Energetic Ion Bombardment. Marcela M. Bilek1, Daniel V. Bax1,2, Alexey Kondyurin1, Neil J. Nosworthy1,3, Yongbai Yin1, Stacey Hirsh1,3, David R. McKenzie1 and Anthony S. Weiss2; 1School of Physics, University of Sydney, Sydney, New South Wales, Australia; 2School of Molecular Biosciences, University of Sydney, Sydney, New South Wales, Australia; 3School of Medical Sciences, University of Sydney, Sydney, New South Wales, Australia.

The ability to strongly attach biomolecules such enzymes and antibodies to surfaces underpins a host of technologies which are rapidly growing in utility and importance. Such technologies include biosensors for medical and environmental applications and protein or antibody diagnostic arrays for early disease detection. Emerging new applications include continuous flow reactors for enzymatic chemical, textile or biofuels processing and implantable biomaterials[1] that interact with their host via an interfacial layer of active biomolecules to direct a desired cellular response to the implant. In many of these applications it is desirable to maintain physical properties (including mechanical and electrical) of an underlying material whilst engineering a surface suitable for attachment of proteins or peptide constructs. Nanoscale polymeric interlayers are attractive for this purpose. We have developed interlayers which form the basis of a new biomolecule binding technology with significant advantages over other currently available methods[2]. The interlayers, created by the ion implantation of polymer like surfaces[3,4], achieve covalent immobilization on immersion of the surface in protein containing solution. Since chemical linkers are not required, the surface chemistry can be tailored independently to optimize the bioactivity. The interlayers can be created on any underlying material and ion stitched into its surface. The covalent immobilization of biomolecules from solution is achieved through the action of highly reactive free radicals in the interlayer. In this paper, we present characterisation of the structure and properties of the interlayers and describe a detailed kinetic model for the covalent attachment of protein molecules directly from solution. The universality with respect to biomolecules and the ability to decouple surface chemistry from covalent immobilization capability will be discussed. Prospects for applying this technology for directing cell growth and to create biosensors or protein microarrays will be explored. References: [1] Bax DV, McKenzie DR, Weiss AS, Bilek MMM, Biomaterials, 31: 2526-2534 (2010) [2] Bilek M, McKenzie DR, Biophysical Reviews, 2(2) 55-65 (2010). [3] M. Bilek, D.R. McKenzie, R.C. Powles, “Treatment of polymeric biomaterials by ion implantation” in Biomaterials and Surface Modification (ed. P.K. Chu and X. Liu)”, Research Signpost 2007. [4] YB Yin, K Fisher, NJ Nosworthy, D Bax, S Rubanov, B Gong, AS Weiss, DR McKenzie, MMM Bilek, Plasma processes and polymers, 6(10) 658-666 (2009).


9:00 AM *II1.3
Enhancement of Surface Bioactivity and Biocompatibility of Materials Using Plasma, Energetic Ions, and Related Techniques. Paul K. Chu, Physics and Materials Science, City University of Hong Kong, Kowloon, Hong Kong.

Plasma-based ion implantation and deposition (PBII&D) is a useful technique in many applications such as biomedical engineering. In addition to the ability to modify materials surfaces, novel structures can be fabricated. Another advantage is that the surface characteristics such as mechanical properties and biocompatibility can be selectively enhanced with the favorable bulk attributes of the materials unchanged. In this invited talk, recent research works conducted in our laboratory pertaining to biomedical engineering will be described. Topics to be presented include fabrication of novel nanostructures on biomaterials, biopolymers, and spinal implants.


9:30 AM *II1.4
Neural Cell Attachment Studies on Metal-Gas Hybrid Ion Implanted Biodegradable Polymers. Emel Sokullu Urkac1, Ahmet Oztarhan1, Ismet D. Gurhan1, Sultan Gulce Iz1, Feyzan Odal Kurt2, Funda Tihminlioglu3 and Bercin Isikli3; 1Bioengineering Department, Ege University, Izmir, Turkey; 2Biology Department, Celal Bayar University, Manisa, Turkey; 3Chemical Eng. Department, Izmir Institute of High Technology, Izmir, Turkey.

Our aim is to prepare neuronal growth stimulation on the surface modified biodegradable polymers for artificial neural networks. For this we used metal and metal+gas hybrid ion implantation technique to determine the best condition for neural guidance and nerve cell attachments on biodegradable polymer surfaces. As biodegradable polymer samples, lactide derivatives; Poly L-Lactide(PL), Poly-DL-Lactide Glycolide(PDLG), Poly Caprolactone(PCL) and Chitosan were implanted by C+ , Au+ and C++N+ ions by using Metal-Vapour Vacuum Arc (MEVVA) ion implantation technique. Samples were implanted with a fluence of 1014 , 1015 , 1016 ion/cm2 and extraction voltage of 20, 30 and 40 kV. The Chitosan, PLA, PDLG and PCL samples were prepared by solvent casting method with different solutions in %3-5. In vitro neeural cell culture studies have been carried out with model cell lines (PC12 and Kelly) to show that ion beam modified surfaces can stimulate the neural growth on biodegradable polymeric surfaces. Scanning electron microscopy (SEM) was used to examine the cell attachments on the surface. The best results were obtained with Au+ implantation with fluence of 1016 ion/cm2 and extraction voltage of 30 kV. Chemical surface characterisation of ion beam implanted samples were also studied by XPS, FTIR and Raman. Contact angle measurements were done. We tried to find the correlation between cell growth and cell attachment, and modified surface properties of biodegradable polymers.


 

SESSION II2: Patterning and Lithography
Chair: Daryush Ila
Tuesday Morning, April 26, 2011
Room 3016 (Moscone West)


10:30 AM *II2.1
Patterned Ion Implantation into Amorphous and Crystalline SiO2 for 3D Nanofabrication. Naoki Kishimoto1, Bangke Zheng2, Debi Prasad Datta2, Keisuke Sato3 and Yoshihiko Takeda2; 1National Insitute for Materials Science, Tsukuba, Ibaraki, Japan; 2Quantum Beam Center, National Institute for Materials Science, Tsukuba, Ibaraki, Japan; 3Dept. of Physics, University of Bologna, Bologna, Italy.

Ion implantation is a robust and efficient tool to fabricate well-defined nanostructures for novel functional devices, having advantages of arbitrary atomic injection and good spatial controllability. If the lateral control of ion beams is accomplished in addition to the inherent depth control, the three dimensional (3D) nanofabrication will be realized. There are several approaches to the lateral control of ion implantation, such as masked implantation, FIB, ion projection patterning. As one of the future targets, metal nanoparticle systems are promising for plasmonic applications, such as for ultra-fast switching, near-field devices. In this paper, we present ion-beam-based methods for micro- and nano-patterning for 3D nanostructures and discuss attainable spatial resolutions for patterning. We conducted patterned ion implantation of 60 keV Cu- into amorphous (a-) or crystalline(c-) SiO2, by using either an anodic porous alumina membrane as a self-assembled/patterned mask or a patterned Si-membrane mask. The porous alumina can be efficiently fabricated and demonstrated successful patterned implantation of nano-sized periodic spots, down to 100 nm in diameter. The nano-patterned Si masks made from SOI membranes were also employed for the patterned ion irradiation. When the patterned ion implantation was applied to c-SiO2, nanopatterning of radiation-induced swelling was accomplished with minimal blurring of the spot size. The patterning of nanoparticle assembly was succeeded by these methods, but the precipitation tendency of patterned implantation was less than those of the ordinary wide-area implantation. The less precipitation tendency is due to the nano-scale effect, e.g., the proximity effect of nano-sized domains. The results of masked implantation indicate that not only the atom-supply control but also additional material control is necessary to accomplish the desired functionality. The scope of 3D nanofabrication for plasmonic applications will be discussed.


11:00 AM II2.2
Multi-scale Patterning, Using Ion Beam Processing in Combination with Self-Assembly. John Baglin, IBM Almaden Research Center, San Jose, California.

Advanced device fabrication demands the development of robust and reliable techniques capable of imposing extended patterns of multi-scale features, with critical requirements for minimum line edge roughness (LER) and feature width, and high aspect ratio. Also important is avoidance of proximity effects between neighboring features. These items remain high priorities for the semiconductor industry roadmap, as well as in other areas of nanotechnology. In this presentation, we describe recent experiments using low energy ion beams, in combination with novel strategies of self-assembly, to achieve high resolution patterns with reduced LER, and features displaying nanometer edge definition.


11:15 AM II2.3
Elucidating on Scalable Nanopatterning Mechanisms of III-V Semiconductors with In-situ Surface Characterization. Osman El-Atwani1,4, Alex Cimaroli2, Sami Ortoleva3 and Jean Paul Allain1,2,4; 1Mateirals Engineering, Purdue University, West Lafayette, Indiana; 2Nuclear Engineering, Purdue University, West Lafayette, Indiana; 3Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana; 4Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana.

It is well known that several nanostructures shapes and sizes can be formed via ion beam sputtering (IBS) techniques. Several speculations are available in literature regarding the formation mechanism of nanostructures (dots and pillars) via IBS. Some discussions are based on quantitative and qualitative analysis of the nanostructures at different irradiation times or doses. Moreover, the role of oxygen in the formation mechanism of the nanostructures is almost neglected. The oxide layer on top of gallium antimonide substrates plays a role in the differential sputtering mechanism. Gallium and antimony sputtering yields are not that different since their surface binding energies are nearly the same. However, Gallium oxide is a very strong bond compared to antimony oxide, thus, differential sputtering of antimony will be enhanced. The formation of gallium oxide is improved due to the following reaction: Sb2O3 + 2GaSb → Ga2O3 +4Sb Equation 1 In this study, two different sets of experiments are performed of gallium antimonide substrates. In the first set of experiments, gallium antimonide substrates are irradiated at the low and high energies with argon ion beam. In-situ XPS and ISS characterization are preformed on the samples at different fluencies. The results are accompanied with ex-situ SEM and TEM morphology characterization. In the other set of experiments, however, similar work was performed on gallium antimonide but under ex-situ conditions, where the samples were revealed to atmosphere before XPS and ISS characterizations. All irradiations and chemical characterizations were performed in the Particle and Irradiation Interaction of Hard and Soft Matter (PRIHSM) facility in the Nuclear Engineering at Purdue. XPS results indicated the strength of gallium oxide over antimony oxide. The antimony oxide peak vanished much before the gallium oxide peak. Quantification of the results showed vast differences between the results of the ex-situ and in-situ experiments. The results demonstrate that it is crucial to perform the nanostructures formation mechanism studies under in-situ conditions. Results from ex-situ performed experiment are in the most cases misleading. As an example, irradiation of gallium antimonide using argon ion beam at 100eV was performed. In-situ characterization using ISS and XPS showed 45% and 35% of gallium relative concentration respectively. When the samples was revealed to atmosphere and characterized with ISS and the XPS, the results changed to 54% (ISS) and 45% (XPS) of gallium relative concentration. Ex-situ results showed more gallium oxide on the surface. This is due to preferential reduction of oxygen on the surface. The results can show more gallium on the surface if exposed more to atmosphere and due to the reaction in equation 1.


11:30 AM II2.4
Modeling of Approximated Electron Transport across Ion Beam Patterned Quantum Dot Nanostructures. Jonathan S. Lassiter1, John Chacha2, Claudiu Muntele3, Satilmis Budak2, Abdalla Elsamadicy1 and Daryush Ila4,3; 1Physics, University of Alabama in Hunsville, Huntsville, Alabama; 2Elecrical Engineering, Alabama A&M University, Normal, Alabama; 3Center of Irradiation of Materials, Alabama A&M University, Normal, Alabama; 4Physics, Alabama A&M University, Normal, Alabama.

High energy ion beams are used to modify co-deposited nanolayer films of alternated materials (i.e. insulator and metal, two different semiconductors, even more complex arrangements), to form nanodots through localized nucleation. The particular application being considered is for high efficiency thermoelectric conversion systems. The performance of a thermoelectric converter is generally given by the figure of merit, ZT, which is a function of the Seebeck coefficient, electrical conductivity, and thermal conductivity. A performant device would have a maximized electrical conductivity and a minimized thermal conductivity (maximum electron transport, minimal phonon transport). The current models of electron and phonon transportation through 1D, 2D, 3D quantum regimented structures assume an infinitely repetitive perfect structural “cell”, with complicated algorithms requiring intensive computing power. The main focus for this modeling effort is to reduce the three-dimensional problem to a single dimensional approximation without sacrificing the quality of the result. The nanostructure being investigated has Si quantum dots arranged with perfect periodicity in all three Cartesian directions, with the heat and electricity flow monitored in the z-direction (cross-plane as initially layered). Non-Equilibrium Green Functions Formalism (NEGF) is the mode for calculating the theoretical electrical properties assuming a one-dimensional quantum well arrangement in the z-direction with finite boundaries in the x and y directions). The results are to be compared with experimental measurements on such structures.


11:45 AM II2.5
MeV Si Ions Modifications on Thermoelectric Properties of SiO2/SiO2+Cu Multilayer Films. Satilmis Budak1, J. Chacha1, M. Pugh1, C. Smith2,3, K. Heidary1, R. B. Johnson3, C. I. Muntele2 and D. Ila2,3; 1Electrical Engineering, Alabama A.&M. University, NORMAL, Alabama; 2Center For Irradiation of Materials, Alabama A&M University, Normal, Alabama; 3Physics, Alabama A&M University, Normal, Alabama.

We made 100 periodic nano-layers of SiO2/SiO2+Cu multiplayer thin films using DC/RF sputtering. The performance of the thermoelectric materials and devices is shown by a dimensionless figure of merit, ZT = S2σT/k, where S is the Seebeck coefficient, σ is the electrical conductivity, T is the absolute temperature and k is the thermal conductivity. ZT can be increased by increasing S, increasing σ, or decreasing k. Rutherford Backscattering Spectrometry (RBS) and RUMP simulation software were used to determine the stoichiometry of SiO2, Cu in the multilayer films and the thickness of the grown multi-layer films. The 5 MeV Si ions bombardment was performed using the AAMU Pelletron ion beam accelerator, to make quantum clusters in the multi-layer superlattice thin films, to decrease the cross plane thermal conductivity, increase the cross plane Seebeck coefficient and cross plane electrical conductivity. *Corresponding author: S. Budak; Tel.: 256-372-5894; Fax: 256-372-5855; Email: satilmis.budak@aamu.edu Acknowledgement Research sponsored by the Center for Irradiation of Materials (CIM), National Science Foundation under NSF-EPSCOR R-II-3 Grant No. EPS-0814103, DOD under Nanotechnology Infrastructure Development for Education and Research through the Army Research Office # W911 NF-08-1-0425.


 

SESSION II3: Focused Beams and Ion Cluster Beams
Chair: John Baglin
Tuesday Afternoon, April 26, 2011
Room 3016 (Moscone West)


1:30 PM *II3.1
Cluster Ion Beam Processing: Review of Current and Prospective Applications. Isao Yamada, Graduate School of Engineering, University of Hyogo, Himeji, Hyogo, Japan.

Cluster ion beam processes which employ ions comprised of a few hundred to several thousand atoms are being developed into a new field of ion beam technology. The concurrent energetic interactions between many atoms comprising a cluster and many atoms at a target surface result in highly non-linear sputtering and implantation effects and produce impact processes that are fundamentally different from those associated with the more simple binary collisions which take place during monomer ion impacts. Cluster ion beam processes are characterized by low energy surface interaction effects, lateral sputtering phenomena and high-rate chemical reaction effects. This paper reviews the current status of the studies of the fundamental ion-solid interactions, the present industrial applications and trials underway towards new prospective applications. Much fundamental research has explored cluster ion-solid surface phenomena and beam transport characteristics. Recent contributions have emphasized cluster size (atoms/cluster) dependences of beam transport and process characteristics. Cluster size dependences of sputtering, surface damage and implantation ranges have been examined both experimentally and by MD simulations. Recent successful industrial applications for device fabrications are shallow junction formation for FET (using the low energy effect of poly atomic cluster ion implantation), local corrective etching for bulk acoustic wave devices (using the lateral sputtering effect of gas cluster ion beam, GCIB) and surface planarization of patterned media for HDD (using the low energy and lateral sputtering effects of GCIB). Processes with nano scale accuracy are being achieved, for example in formation of shallow junctions of depth less than a few nm, and in smoothing of surfaces to roughness less than 1 nm. Other new uses for GCIB processing are being developed. One example is in the field of surface modification of bio-materials. It has been shown that GCIB modification of titanium can greatly enhance osteoblast proliferation and bone formation. A novel method of drug delivery from metal vascular stents employs GCIB to control rate of elution without requiring the use of any binding polymer. Another new area of application for GCIB is in surface analyses such as XPS and SIMS. Because a large cluster can sputter from a much shallower volume of material than in the case of a smaller projectile, GCIB can be beneficially employed to accomplish extremely surface-sensitive analyses of organic thin films. Many examples have been shown of the usefulness for analyses of organic materials with large molecular mass such as EL materials and proteins.


2:00 PM *II3.2
Helium Ion Microscopy Techniques for Imaging Soft Materials and Nanostructures. Shinichi Ogawa, Nanodevice Innovation Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba-city, Ibaraki-ken, Japan.

The imaging of fine line features patterned in low-k (dielectric constant) (k < 2.5) materials is important for LSI Cu / low-k interconnect validation of the dry etch, wet clean, and ash in back end process steps. Conventional secondary electron microscope (SEM) imaging of low-k materials often results in changes to the low-k material line width, edge roughness, and shape. This makes SEM interpretation of the real shape difficult because of structural damage during the SEM electron beam irradiation. Additionally, at the low accelerating voltages required to image low-k materials in an SEM, contrast is poor and pattern transfer fidelity is subsequently hard to qualify. We have investigated the ability of helium ion microscopy (HIM) 1) to provide low-k dielectric images that contain pattern information not available with a conventional SEM. The helium ion interaction with low-k materials was also investigated 2), 3). During this investigation, a potential new application, the imaging, through the inter-level dielectric, of the underlying copper, was explored as well. The ion / sample interaction physics differentiates the helium ion microscope from a conventional SEM from the point of view of thermal energy transfer into a unit volume of the low-k material. The helium ion microscope, Orion (Carl Zeiss), was used in this study and the resolution on graphite material obtained so far was 0.21 nm in our experiments. In a case of carbon materials characterization, phenomena are quite the same. Recent imaging results from the carbon materials will be discussed and compared to TEM results. I would like to acknowledge W. Thompson and L. Stern of Carl Zeiss Inc. for their assistance in the Cu/Low-k work and T. Iijima and M. Nihei of AIST for their collaboration with the carbon materials work. References : 1) L. Scipioni, W. Thompson, S. Sijbrandij, and S. Ogawa: Proc. Int Reliability Physics Symp., 2009, p. 317, 2) W. Thompson, S. Ogawa, L.Stern, L. Scipioni, and J. Notte,, Proc. of International Interconnect Technology Conference p.69 (2009), 3) S. Ogawa, W. Thompson, L. Stern, L. Scipioi, J. Notte, L. Farkas, and L. Barriss, Jpn. J. Appl. Phys., 49 (2010) 04DB12


2:30 PM *II3.3
Emerging Applications Of Helium Ion Microscopy. Diederik J. Maas1, Emile van Veldhoven1, Paul F. Alkemade2, Henny W. Zandbergen2 and Emile W. van der Drift2; 1Semicon Equipment, TNO - van Leeuwenhoek Laboratory, Delft, Netherlands; 2Kavli Institute of Nanoscience, Delft University of Technology, Delft, Netherlands.

Although Helium Ion Microscopy was introduced only a few years ago [1], many new application fields are budding. The connecting factor between these novel applications is the unique interaction of the primary helium ion beam with the sample at and just below its surface. The sub-nanometer sized probe of the 10-35 keV ion beam generates Secondary Electrons (SEs) that have a typical energy between 0 and 20 eV. In most materials, the mean free path of the SEs is of the order of a few nanometers. Hence the SE signal stems from an area that is very well localized around the point of incidence of the primary beam. This makes the HIM well-suited for both high-resolution imaging as well as high resolution nanofabrication [2]. An extra advantage in nanofabrication is the low ion backscattering fraction, leading to a weak proximity effect. The lacking of a quantitative materials analysis mode (like EDAX as in Scanning Electron Microscopy, SEM) and a relatively low beam current are the present drawbacks of the HIM. The HIM is a high-resolution surface imaging tool. In practice, the optimum dose for imaging is a balance between maximizing S/R while minimizing sample damage. Imaging work at TNO van Leeuwenhoek Laboratory (VLL) [3] focuses at sensitive materials such as e.g. Organic Photo Voltaic materials, DUV and EUV resists, which are difficult to image in a SEM due to their charging behavior. An electron flood gun in the HIM offers effective charge cancellation, which enables high-resolution imaging. Next to the generation of SEs, sample interaction also comprises helium implantation, neutralization, backscattering and some sputtering of target atoms. The gentle milling with the Helium ions can be used to create sub-10 nm wide cuts in a variety of materials, demonstrating the very local interaction of the helium ions. Furthermore the cutting of materials with this nanometer precision enables the preparation of ultrathin TEM samples that have a very thin amorphous layer. Compared with TEM sample preparation with the Gallium FIB, HIM cutting offers better precision combined with less damage on at least some materials. As a result, artifacts in TEM imaging due to the sample preparation can be reduced, while imaging is improved. Furthermore, to explore the possibilities of the helium ion microscope as a nanofabrication tool, the HIM at the TNO VLL is equipped with a pattern generator and a gas injection system. This presentation will also touch on the latest lithography results as well as nanostructures made with Helium Ion Beam Induced Processes like deposition and etching. References [1] J. Morgan, J. Notte, R. Hill, and B. Ward, Microscopy Today 14, (2006) 24 [2] D.J. Maas et al., Proc. SPIE Vol. 7638, 763614 (2010) 1-8 [3] http://www.vanleeuwenhoeklab.com/


3:30 PM II3.4
Helium Ion Milling Structured Graphene Transistor. Kaiwen Zhang1,5, Xiangming Zhao1,5, Xiangfan Xu1, Viswanathan Vignesh2, Baowen Li1,4,5, Venky Venkatesan Venkatesan2,3, Daniel S. Pickard2,3 and Barbaros Oezyilmaz1,3,4; 1Physics, National University of Singapore, Singapore, Singapore; 2Electrical and Computer Engineering, National University of Singapore, Singapore, Singapore; 3NanoCore, National University of Singapore, Singapore, Singapore; 4NUS Graduate School for Integrative Science and Engineering, National University of Singapore, Singapore, Singapore; 5Centre for Computational Science and Engineering, National University of Singapore, Singapore, Singapore.

We report the direct patterning of graphene for various nano-device applications. The Helium Ion Microscope (HIM), able to resolve nano-scale features on solid samples with an edge resolution of a mere 0.25 nm, has a number of attributes which make it attractive for the imaging of graphene structures. Even more compelling is the ability to directly modify graphene, through surface sputtering, enabling direct pattern transfer for the fabrication of graphene devices. The integration of the HIM with a vector pattern generator (Nano Pattern Generation System, NPGS), provides the capability to directly pattern graphene into nano-ribbons. We have successfully fabricated sub-50nm graphene nano-ribbon devices on Si/SiO2 substrate. Resistance measurement has been executed as a function of temperature. We will discuess the recent results of properties in such narrow graphene transistor. For future research, we will use HIM to pattern graphene into nano-devices for the study of electrical and thermal properties.


3:45 PM *II3.5
Multi-ion Beam Lithography and Processing Studies. Bill R. Appleton1, Sefaattin Tongay1, Maxime Lemaitre1, Brent Gila1 and Joel Fridmann2; 1Nanoscience Institute for Medical and Engineering Technologies, University of Florida, Gainesville, Florida; 2Raith USA Inc., Ronkonkoma, New York.

Ion beam processing and nanofabrication results are reported for a new multi-ion beam system capable of ion beam lithography, sputter profiling, maskless ion implantation, ion beam mixing, ion channeling, and in situ imaging; all with spatial and temporal patterning over (100 x 100 mm2) areas with nanometer precision. Currently this system uses AuSi and Ga liquid metal alloy ion sources (LMAIS) and an ExB filter to produce Au, Si, and Ga ions and ion clusters at voltages from 15 - 40 kV, and is coupled with a precision laser interferometer stage for sample manipulation and patterning. Results will be reported utilizing the nanometer precision and direct-write capabilities to investigate: 1) Ion induced surface instabilities in Ge. A long-standing surface anomaly is produced in the amorphous phase of Ge by energetic ion bombardment that depends on ion species/energy/dose, and substrate conditions. How this anomaly is affected when using nanoscale ion beams at varying energy, dose rate, dimensional, and temporal parameters will be reported for Si and Au ions, and Au clusters. 2) Nanocrystalline arrays. Nanometer beams of Si and Au can be implanted in virtually any substrate and in predetermined patterns using the maskless implantation and the lithographic capabilities of the system. These techniques will be used to fabricate Au and Si nanocrystalline arrays similar to those that have been fabricated by conventional lithographic techniques and widely studied for their potential optical and electronic applications. The structural (TEM and SEM) and luminescence properties of these arrays will be reported. 3) Fabrication of nanoelectronic device features. It will be demonstrated that the combination of nano-ion beam lithography, and the access to multiple ion species can provide significant advantages for fabricating prototype nanoelectronic device structures. It will be shown that when Au instead of conventional Ga ions is used to mill device features in GaAs it is possible to avoid residual Ga that is often left and must be removed by post-processing that can roughen the surface. Similarly, without removing the sample it is possible to switch to Si ions for maskless implantation doping of the GaAs device. It will also be shown that Si and Au beams can be used to advantageously pattern graphene for device and sensor applications. The current ion beam system is capable of operating with a variety of LMAIS sources and thus can potentially produce a wide range of ion species. Since multi-charged ions and charged cluster-ions are also produced it is possible to enhance the energy range of the system. All these capabilities extend the potential for future applications.


4:15 PM II3.6
3D Silicon Nanostructure Fabrication via Thin Film Focused Ion Beam Milling in Combination with Metal-assisted Chemical Etching. Konrad Rykaczewski1, Owen Hildreth3, Ching P. Wong3, Andrei Fedorov2 and John Henry J. Scott1; 1MML, NIST, Bethesda, Maryland; 2G. W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia; 3School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia.

Metal-assisted Chemical Etching (MaCE) of silicon is a new method to fabricate complex 1D, 2D, and 3D silicon nanostructures. In this process, silicon etching is confined to a small region surrounding metal catalyst nanoparticles, thin films or shaped structures that travel in three dimensions during the etching process. Dependent on the combination of the metal structures shape and the composition of the etchant solution, the catalyst motion during etching can be random producing porous silicon [1] or it can occur along a well defined path resulting in formation of vertical [2-5], slanted [6, 7], zigzagged [8], and spiral [9] structures in silicon. Area-selective MaCE of silicon can be achieved by directly patterning the metal using methods such as photo- and electron beam- lithography [4, 9]. However, these methods are only capable of fabrication of structures with uniform thickness on a planar surface. In this work, we demonstrate that FIB milling of Au films to different thicknesses prior to etching leads side-by-side fabrication of 3D structures, nanowire arrays, and porous silicon patterns. Furthermore, we demonstrate that unique capabilities of FIB allow for metal patterning on multiple silicon faces under different orientations and simultaneous etching of protrusions in varied directions. The etched out 3D silicon structures have characteristic feature sizes ranging from ~50-100 nm to several micrometers and aspect ratio of 1:10-1:20. References1. Li, X. and P.W. Bohn, Applied Physics Letters, 2000. 77(16): p. 2572-2574.2. Tsujino, K. and M. Matsumura, Advanced Materials, 2005. 17(8): p. 1045.3.Lee, C.L., et al., Journal of Materials Chemistry, 2008. 18(9): p. 1015-1020.4.Chun, I.S., et al., Applied Physics Letters, 2008. 92(19): p. 3. 5.Rykaczewski, K., et al., Acs Applied Materials & Interfaces, 2010. 2(4): p. 969-973.6.Peng, K., et al., Advanced Functional Materials, 2008. 18(19): p. 3026-3035. 7.Chern, W., et al., Nano Lett. 10(5): p. 1582-8. 8.Chen, H., et al., Nano Letters. 10(3): p. 864-868. 9.Hildreth, O.J., et al., ACS Nano, 2009.


4:30 PM II3.7
Influence of Focused Ion Beams on the Growth of GaN/SiNx Nanocomposites. Justin Canniff1, Adam Wood2 and Rachel Goldman1,2; 1Materials Science and Engineering, University of Michigan at Ann Arbor, Ann Arbor, Michigan; 2Physics, University of Michigan, Ann Arbor, Michigan.

Nanocomposites consisting of quantum dots within a matrix have been proposed for high efficiency photovoltaics and high figure-of-merit thermoelectrics [1]. We recently developed a promising approach, matrix-seeded growth, to producing semiconductor nanocomposites which involves ion-beam-amorphization of a semiconductor film, followed by annealing [2]. For example, we have synthesized GaN-rich nanocrystals within an amorphous GaAsN matrix using N-ion implantation into epitaxial-GaAs, followed by rapid-thermal-annealing. Remarkably, these nanocomposites exhibit significant near-infrared photoluminescence and cathodoluminescence, indicating sufficient crystallinity for several active device applications. Here, we demonstrate a similar approach for GaN/SiNx nanocomposites. We have investigated the formation of GaN in SiNx using Ga+ focused-ion beam irradiation of amorphous SiNx membranes followed by rapid thermal annealing. For these experiments, amorphous SiNx membranes with 0.1 mm2 area windows and thicknesses of 500 nm were implanted with normal incidence Ga+ ions, with net doses of 3.3e18 cm-2 to 8.3e18 cm-2. Patterned arrays were implanted at 30 kV, ~5.5 pA, with 4 x 8 arrays consisting of ~35 nm diameter spots with ~100nm center-to-center spacing. Some of these samples were then bulk implanted at 5 kV at a dose of 3.0e18 cm-2. Other samples without patterned arrays were bulk implanted at 5, 10, 20, and/or 30 kV at a dose of ~5e17 cm-2. Following FIB implantation, the samples were annealed in a 1000 sccm N2 environment for 1-16 minutes at 900 C in a rapid thermal annealer. Electron diffraction reveals the nucleation of zincblende GaN nanocrystals while the SiNx matrix remains amorphous. We will discuss how ion implantation damage, local [Ga], and annealing time enhance the nucleation and growth of GaN nanocrystals within amorphous SiNx. We will also discuss the thermal transport properties of these 2D GaN/SiNx nanocomposities and progress towards the fabrication of 3D nanocomposites using our UHV FIB-MBE system. This work was supported in part by AFOSR-MURI and ARO-DURIP. [1] Woochul Kim, Joshua Zide, Arthur Gossard, Dmitri Klenov, Susanne Stemmer, Ali Shakouri, and Arun Majumdar. “Thermal Conductivity Reduction and Thermoelectric Figure of Merit Increase by Embedding Nanoparticles in Crystalline Semiconductors.” PRL 96, 045901 (2006). [2] X. Weng, R.S. Goldman, V. Rotberg, N. Bataiev, and L.J. Brillson, "Origins of Luminescence from Nitrogen Ion Implanted Epi-GaAs", Appl. Phys. Lett. 85, 2774 (2004).


4:45 PM II3.8
Nanomechanical Resonators Grown by Focused-ion-beam Deposition. Huan Wang, Olivio Chiatti, Jon C. Fenton and Paul A. Warburton; London Centre for Nanotechnology, London, United Kingdom.

Resonators with nanoscale physical dimensions have exhibited excellent sensitivity by comparison with micromachined cantilevers and therefore show potential advantages for application as sensitive mass balances. We have fabricated vertical tungsten nanowires on silicon substrates, using focused ion beam (FIB)-assisted chemical vapour deposition with an accelerating voltage of Ga+ of 30 keV and a constant beam current of 1 pA. The length, L, of the nanowires varied from 10 to 70 μm and the diameter, 2r, varied from 150 to 250 nm. The growth rate was approximately 0.053 μm3s-1. One group of vertical nanowires were cut at their base by the FIB. The nanowire fell over and was suspended over a trench. Further tungsten was deposited over the ends to make either a doubly-clamped beam or a singly-clamped beam. The Young’s modulus of these beams was investigated by force-displacement bending measurements using an atomic force microscope (AFM) and was found to be in the range 120 -180 GPa. Another group of vertical tungsten nanowires were excited by a piezo-electric actuator in an SEM chamber. SEM linescans across the nanowire were employed to analyze the forced oscillations, with a noise floor of 5 nm for measurements of the oscillation amplitude. The resonant frequency was found to scale with r/L2 in accordance with standard cantilever theory. Preliminary measurements up to about 300 kHz show that the Q factor is around 440, independent of the resonant frequency. Based on the current results, we extrapolate that the mass resolution should reach a few attograms for a nanowire with a length of 5 μm and a radius of 40 nm.


 

SESSION II4: Graphene, Diamond, Carbon
Chair: Diederik Maas

Wednesday Morning, April 27, 2011
Room 3016 (Moscone West)


8:30 AM II4.1
Graphene Imaging and Patterning with the Helium Ion Microscope. William B. Thompson1, Lewis Stern2, David Ferranti2 and Larry Scipioni2; 1Helium Ion Microscope, Carl Zeiss NTS, Los Altos, California; 2Helium Ion Microscope, Carl Zeiss NTS, Peabody, Massachusetts.

Helium ion microscope (HIM) resolution improvements have made feasible the imaging of thin materials like graphene with potentially atomic resolution. Highly ordered pyrolitic graphite (HOPG) and suspended sheets of graphene were imaged to assess the microscope’s ability to see the graphene lattice. We will review the HIM system fundamentals and discuss our interpretation of recent HIM HOPG and graphene images and their image FFT’s. Researchers have recently demonstrated the HIM patterning of free standing, minimally damaged, graphene ribbons as small as 5 nm in width. Similar results have been obtained with graphene deposited on SiO2. In the later case, measurements of the electrical properties of graphene were also made. As the band structure of graphene depends on the electron wave-vector in the carbon lattice, the ability to constrain the graphene ribbons, with a minimal introduction of carbon defects, to align with the directions of the high symmetry points K and M (the armchair and zigzag ribbon directions) could provide benefit to researchers studying the electronic properties of graphene. A summary of patterned single sheet graphene “sputter” yields and their relationship to the Rutherford elastic recoil cross section will be presented. From molecular dynamics (MD) simulation, we have estimated the minimum patternable hole in monolayer and bilayer graphene. We will conclude with the implications of this simulation and the potential applications for the HIM imaging and patterning of graphene at the atomic level.


8:45 AM II4.2
Focused Ion Beam Fabrication Of Planar Diamond Nanowire Devices. Alfredo M. Morales1, Richard J. Anderson1, Nancy Y. Yang1, Benjamin Van Blarigan1, Michael J. Rye2 and Jack L. Skinner1; 1Sandia National Laboratories, Livermore, California; 2Sandia National Laboratories, Albuquerque, New Mexico.

The properties of diamond such as its wide band gap, negative electron affinity, chemical and biological inertness, radiation hardness, and high thermal conductivity make it a promising material for applications in electronics, chemical/biological detection, and radiation monitoring. However, in order to systematically explore the properties of diamond and in order to explore possible size effects, a deterministic method to fabricate diamond transistor devices with ohmic contacts is needed. Focused ion beam (FIB) etching has been previously used to fabricate electron thin diamond specimens for electron microscopy. We now report our work modifying FIB etching of diamond samples to produce planar nanowire diamond transistor devices. The deterministic FIB patterning method was demonstrated on poly- and single-crystal diamond films producing diamond nanowire transistors. The fabrication method produced self registering platinum metal contacts on the nanowires allowing for facile device testing using standard micromanipulators. Raman analysis of the diamond devices showed that some tetrahedral amorphous sp3 carbon was produced by the fabrication process but electron microscopy, secondary ion mass spectroscopy, and x-ray photoelectron spectroscopy of the diamond showed no bulk distortion of the lattice and no incorporation of the gallium FIB ions. Device testing of boron doped polycrystalline devices clearly showed a semiconductor response. Current injection across the platinum-diamond interface required lower potential than injection across a tungsten oxide-diamond interface.


9:00 AM II4.3
Ion Micro-beam Fabrication of Single-crystal Diamond. Paolo Olivero1, Federico Bosia1, Daniele Gatto Monticone1, Federico Picollo1, Hao Wang1, Ettore Vittone1, Silvia Calusi2, Mirko Massi2, Lorenzo Giuntini2, Emanuele Enrico3, Luca Boarino3, Giampiero Amato3, Zeljko Pastuovic4, Natko Skukan4, Milko Jaksic4, Andrea Sordini5, Maurizio Vannoni5, Anna Sytchkova6, Stefano Lagomarsino7, Silvio Sciortino7, Barbara Fairchild8, Sergey Rubanov8 and Steven Prawer8; 1Experimental Physics Department, University of Torino, Torino, Italy; 2Physics Department, INFN Firenze, University of Firenze, Firenze, Italy; 3Quantum Research Laboratory, NanoFacility Piemonte, National Institute of Metrologic Research, Torino, Italy; 4Laboratory for Ion Beam Interaction, Ruder Boskovic Institute, Zagreb, Croatia; 5Istituto Nazionale di Ottica Applicata, CNR, Arcetri, Italy; 6Optical Coatings Group, ENEA Research Centre, Roma, Italy; 7Energetics Department, INFN Firenze, University of Firenze, Firenze, Italy; 8Microanalytical Research Centre, Electron Microscope Unit, Bio 21 Institute, University of Melbourne, Melbourne, Victoria, Australia.

MeV ion implantation is an effective tool in the micro-fabrication and functionalization of a vast range of materials, and in particular it can be effectively adopted to engineer the electrical, optical and structural properties of diamond. The damage density can be controlled over a broad range by varying several implantation parameters, such as ion species and fluence, resulting in the formation of point defects, in the amorphization and eventually in the permanent graphitization of the pristine crystal upon thermal annealing when a critical damage threshold is reached. In this structural modification process, high spatial resolution in both lateral and depth dimensions is allowed respectively by the availability of focused ion beams and by the peculiar damage density profile of highly energetic ions in matter. In particular, since most of the ion matter nuclear interaction occurs at the end of implanted ion range, it is possible to define sub superficial three dimensional structures with engineered physical properties by employing variable-thickness masks. In the present contribution, an overview will be given on our activity in the development of Deep Ion Beam Lithography (DIBL) in diamond, which is envisaged as an ideal tool to fabricate a set of key micro-components (such as optical microstructures, sub-superficial electrodes and buried microfluidic devices) in many applications, ranging from bio-sensing devices to ionizing radiation detectors and integrated optics. In particular the following topics will be addressed: - Fabrication of conductive channels: the conduction mechanisms of diamond damaged with a range of ion species, energies and fluences have been investigated both at room temperature and at variable temperatures, and recent progresses are reported on the realization of buried conductive structures emerging in contact with the sample surface by means of variable-thickness masks; - Controlled variation of the optical properties of ion-implanted diamond: interferometric techniques and localized optical absorption measurements have been employed to directly measure the variation of the real and imaginary parts of the refractive index of diamond implanted in a range of fluences, with the purpose of fabricating waveguiding structures based on refractive index contrast; - Control on the structural modification of the material (crystal structure, internal stresses and strains) induced by ion damage: numerical simulations have been carried with finite element methods of critical structural effects such as surface swelling, which are correlated with direct measurements by means of white-light interferometry. Remarks will be made on relevant technological applications for the above-mentioned structures.


9:15 AM II4.4
Fabrication of Graphene Using Carbon Ion Implantation. Tomeka S. Colon2,1, Cydale C. Smith3,1, John ChaCha4,1, Claudiu I. Muntele1,3 and Daryush Ila3,1; 1Center for Irradiation of Materials, Alabama A&M University, Normal, Alabama; 2Mechanical Engineering, Alabama A&M University, Normal, Alabama; 3Physics, Alabama A&M University, Normal, Alabama; 4Electrical Engineering, Alabama A&M University, Normal, Alabama.

Graphene is a flat monolayer of carbon atoms tightly packed into a two-dimensional (2D) honeycomb lattice and is a basic building block for graphitic materials of all other dimensionalities. It can be wrapped up into 0D fullerenes, rolled into 1D nanotubes, or stacked into 3D graphite. Graphene's high electrical conductivity and high optical transparency make it a candidate for transparent conducting electrodes, required for such applications as touchscreens, liquid crystal displays, organic photovoltaic cells, and organic light-emitting diodes. In particular, graphene's mechanical strength and flexibility are advantageous compared to indium tin oxide, which is brittle, and graphene films may be deposited from solution over large areas. One method to grow epitaxial graphene is by starting with single crystal silicon carbide (SiC). When SiC is heated under certain conditions, silicon evaporates leaving behind carbon that reorganizes into layers of graphene. Here we report on an alternate method of producing graphene by using low energy carbon implantation in a nickel layer deposited on silicon dioxide mechanical support, followed by heat treatment in a reducing atmosphere to induce carbon migration and self-assembly. We used high resolution RBS and Raman spectroscopy for process and sample characterization. Details will be discussed during the meeting.


9:30 AM II4.5
Correlation between Structure and Electrical Transport in Ion-irradiated Graphene Grown on Cu Foil. Grant H. Buchowicz1,2, Jeremy T. Robinson3, Cory D. Cress3, Peter R. Stone1,2, Jeffrey W. Beeman2 and Oscar D. Dubon1,2; 1Materials Science and Engineering, University of California at Berkeley, Berkeley, California; 2Lawrence Berkeley National Laboratory, Berkeley, California; 3Naval Research Laboratory, Washington, District of Columbia.

Graphene, a sheet of sp^2-bonded carbon atoms, is attracting tremendous interest due to its potentially transformative impact across a wide range of applications including advanced electronics and sensing. Until recently, most of the spectacular properties observed and benchmark values reported were from investigations of mechanically exfoliated graphene flakes. However, this method is not ideal for producing uniform and scalable graphene monolayers for practical applications. Graphene grown on copper foils by chemical vapor deposition (CVD) offers an alternative method to produce large-area, monolayer-thick films that can be transferred to a variety of supporting substrates. Because of the more defective nature of CVD-grown graphene due to synthesis and subsequent transferring steps, an important challenge remains to understand the role of imperfections—specifically vacancy-related point defects—on electronic properties. In order to understand the connection between structural quality and transport, we use ion irradiation to controllably introduce defects in graphene. Films grown by CVD and transferred onto SiO2/Si and sapphire substrates were irradiated with a beam of 35 keV carbon ions at fluences ranging from 10^12 cm^-2 to 10^15 cm^-2. Changes in the Raman spectra with increasing ion fluence indicate that the structure of graphene evolves from a highly-ordered layer, to a patchwork of disordered domains, to finally an essentially amorphous film. These structural changes result in a dramatic decrease in the Hall mobility by orders of magnitude while, remarkably, the Hall concentration remains almost unchanged, suggesting that the Fermi level is pinned at a hole concentration near 1x10^13 cm^-2. A model for scattering by irradiation-induced resonant scatterers is in good agreement with mobility measurements up to an ion fluence of 1x10^14 cm^-2. Above this value the mobility has a strong temperature dependence and is indicative of a two-dimensional hopping conduction mechanism like that in amorphous carbon films. This work demonstrates the potential to control the level of disorder induced in a graphene film using ion beams. The work at the Lawrence Berkeley National Laboratory was supported by the Director, Office of Science, Office of Basic Energy Sciences, and Division of Materials Sciences and Engineering of the U.S. Department of Energy under Contract No. De-Ac02-05Ch11231. O. D. D. acknowledges support from the National Science Foundation under contract number DMR-0349257. This work was supported in part by the Office of Naval Research, NRL’s Nanoscience Institute, and the Defense Threat Reduction Agency under MIPR No. 10-2197M.


9:45 AM II4.6
Folding Graphene with Swift Heavy Ions. Sevilay Akcoeltekin1, Hanna Bukowska1, Ender M. Akcoeltekin1, Henning Lebius2 and Marika Schleberger1; 1University of Duisburg-Essen, 47048 Duisburg, Germany; 2CIMAP (CEA-CNRS-ENSICAEN-UCBN), 14070 Caen Cedex 5, France.

Graphene is one of the most promising candidates for future electronic devices due to its outstanding electronic properties [1]. However, up to now there is no established technique to manipulate graphene. For the manipulation of carbon nanostructures ion beams play an important role [2] but so far the impact of swift heavy ions on graphene has not been studied. We have prepared graphene on different single crystal surfaces of SrTiO3, SiO2, Al2O3 and SiO2 by means of mechanical exfoliation [3]. After preparation we checked the graphene flakes with optical microscopy and by Raman spectroscopy to identify single layer or few layer graphene locations and exposed them finally to a beam of swift heavy Xe23+ ions with 95 MeV under oblique angles. Atomic force microscopy reveals that the ions create chains of hillocks in the abovementioned surfaces [4] but not in the graphene itself. If such a chain is created underneath a monolayer of graphene the sheet is ripped apart along the ion track and folds back giving rise to structures resembling origami. For different angles of incidence we find distinct folding patterns of monolayer graphene. Bilayers of graphene are less frequently folded, whereas few layer graphene is not folded at all. [1] A. K. Geim, K. S. Novoselov, 6, Nat. Material. 183-191 (2007). [2] A. V. Krasheninnikov, F. Banhart, Nat. Material., 6, 723-733 (2007). [3] S. Akcöltekin, M. El Kharrazi, B. Köhler, A. Lorke, M. Schleberger, Nanotechnology 20 (2009) 155601. [4] E. Akcöltekin, T. Peters, R. Meyer, A. Duvenbeck, M. Klusmann, I. Monnet, H. Lebius, M. Schleberger, Nat. Nanotechnol 2, 290-294 (2007).


 

SESSION II5: Implantation and Nanostructures I
Chair: Daryush Ila
Wednesday Morning, April 27, 2011
Room 3016 (Moscone West)


10:30 AM *II5.1
Irradiation-induced Phenomena in Carbon and Boron-nitride Nanostructures. Arkady V. Krasheninnikov, Department of Physics, University of Helsinki, Helsinki, Finland; Department of Applied Physics, Aalto University, Espoo, Finland.

Recent experiments (see Refs. [1,2] for an overview) on ion and electron bombardment of nanostructures demonstrate that irradiation can have beneficial effects on such targets and that electron or ion beams can serve as tools to change the morphology and tailor mechanical, electronic and even magnetic properties of various nanostructured materials. It is also evident from the data obtained so far that the conventional theory of defect production in bulk materials not always works at the nanoscale or it requires considerable modifications. We systematically study irradiation effects in nanomaterials, including graphene, carbon nanotubes and other forms of nano-structured carbon. By employing various atomistic models ranging from empirical potentials to time-dependent density functional theory we simulate collisions of energetic particles with carbon nanostructures and calculate the properties of the irradiated systems. In this talk, our latest theoretical results on the response of graphene and carbon nanotubes to irradiation will be presented, combined with the experimental results obtained in collaboration with several groups. The electronic structure of defected graphene sheets with adsorbed transition metal atoms will be discussed, and possible avenues for tailoring the electronic and magnetic structure of graphene by irradiation-induced defects and impurities will be introduced [3]. The effects of ion and electron irradiation on boron-nitride sheets and nanotubes will also be touched upon. Finally, the irradiation response of mechanically strained carbon nanotubes and silicon nanowires will be addressed. [1]Krasheninnikov A. V. and Banhart F., Nature Materials, 6, 723 (2007). [2]Krasheninnikov A. V. and Nordlund K., J. Appl. Phys. (Appl. Phys. Reviews), 107, 071301 (2010). [3] O. Cretu, A.V. Krasheninnikov, J. A. Rodriguez-Manzo, L.Sun, R.M. Nieminen, and F.Banhart. Phys. Rev. Lett. 105 (2010) in press.


11:00 AM II5.2
Fabrication of Ordered Array of Si Nanocrystals in SiO2 by Ultra Low Energy Implantation through Block Copolymer Soft Mask. Michele Perego1, Gabriele Seguini1, Andrea Andreozzi1, Sylvie Schamm-Chardon2, Gerard BenAssayag2 and Paolo Pellegrino3; 1Laboratorio MDM, IMM-CNR, Agrate Brianza, Italy; 2CEMES-CNRS and Univ. de Toulouse, nMat group, Toulouse, France; 3University of Barcelona, Barcelona, Spain.

The fabrication of 2 dimensional arrays of Si nanocrystals (NCs) embedded in SiO2 matrix by ultra-low energy Si implantation and subsequent thermal treatment has been widely investigated in recent years, due to the potential implementation of these nano-structured material in advance microelectronic and optoelectronic devices.[1] This fabrication route is very attractive because of the capability to control size and positioning of the narrow nanocrystal band within the SiO2 matrix and its compatibility with standard conventional silicon technology. Unfortunately this approach does not allow to control lateral distribution of the Si nanoparticles and the fine adjustment of the in-plane nano-structures positioning remains a challenging issue. In this work we present a simple method for the fabrication of spatially organized silicon NCs embedded in a thin SiO2 film by ultra-low energy ion implantation through a nano-structured block copolymer thin film used as a mask. Block copolymer lithography is an emerging nano-lithographic process using self-assembled nanoscale morphologies of block copolymers to fabricate uniform, densely spaced nanometer-scale features over wafer-scale areas.[2] Under suitable processing conditions asymmetric polystyrene-b-poly (methylmethacrylate) (PS-b-PMMA) copolymer thin films naturally self organize forming a PS matrix with hexagonally close-packed PMMA cylinder patterns, perpendicularly oriented with respect to the substrate. After selective removal of PMMA component a nano-porous PS soft mask is formed. The diameter of the pores is about 17 nm and the center-to-center distance is around 33 nm. Implantation is performed with Si+ at energy of 1 keV and two doses 5x1015 and 1x1016 ions/cm2. After removal of block copolymer films, the samples are furnace annealed at 1050°C in N2 during 30 minutes to induce silicon nucleation and growth of NCs. TOF-SIMS measurements on masked and unmasked samples were performed before and after the PS mask removal. On both type of samples the presence of Si excess is detected before annealing at a depth of around 3.5 nm corresponding to the ion projected range at 1 keV. TOF-SIMS profiles indicate that the ratio of Si concentration between the masked silica film and the unmasked reference is about 25 % as expected considering the area of the pores. The characteristics (size, density and in plane distribution) of the silicon NCs population have been investigated by combination of different characterization techniques (SEM, AFM, TEM). The general validity of this methodology to fabricate semiconducting nano-structures is discussed as well. This research activity was funded by the ERANET PLUS “NanoSci-E+” consortium through the NANO-BLOCK project. References: [1] C. Bonafos et al., J. Appl. Phys. 95, 5696 (2004) [2] W. Li, S. Yang J. Vac. Sci. Technol. B 25, 1982 (2007).


11:15 AM II5.3
Synthesis and Characterization of Nanostructures, Formed by Low Energy Carbon Ion Implantation into Silicon Based Matrices. Prakash Poudel1, Antonio Paramo2, David Diercks3, Yuri Strzhemechny2, Bibhudutta Rout1 and Floyd McDaniel1; 1Department of Physics, University of North Texas, Denton, Texas; 2Department of Physics, Texas Christian University, Fort Worth, Texas; 3Center for Advanced Research and Technology, University of North Texas, Denton, Texas.

We present a systematic study of the formation of β-SiC nanostructures by low energy carbon ion implantation into Si followed by high temperature annealing. The effects of thermal annealing in the formation of β-SiC structures has been studied. It is observed that the the thermal annealing of 1100°C for 1 hr is required to observe the formation of β-SiC .The quantitative analysis in the formation of β-SiC nanostructures has been performed by the implantation of various carbon ion fluences in the range of 1×1017 - 8×1017 atoms /cm2 at ion energy of 65 keV into Si. It is observed that the average size of β-SiC crystals decreases whereas the amount of β-SiC increases with the increase in the implanted fluences when the samples were annealed at 1100°C for 1 hr. The amount of β-SiC increases only up to the fluences of 5×1017 atoms /cm2. It appeared to saturate above this fluence. Additionally, we present the formation and characterization of carbon nanoclusters in silica. The carbon nanoclusters were formed by the implantation of 70 keV carbon ions at a fluence of 5×1017 atoms/cm2 into a thermally grown silicon dioxide layer (~500 nm thick) on a Si (100) wafer. The implanted samples were annealed 1100 °C for different time periods of 10 min., 30 min., 60 min., 90 min., and 120 min., in the mixture of argon and hydrogen gas (96 % Ar + 4% H2). Low temperature ( 8K) Photoluminescence results to UV to visible emission (2.0 eV - 3.3 eV) from the samples pointing to carbon clusters, defects, and Si nanostructures as the possible origin of luminescence. Luminescence at 3.3 eV disappears at room temperature measurements. A detail mechanism of the photoluminescence , and its possible origin are discussed. Fourier Transform Infrared spectroscopy, Raman spectroscopy, XRD, X- ray photoelectron spectroscopy, Photoluminescence spectroscopy, and Transmission electron microscopy were used to characterize the samples.


11:30 AM II5.4
Controlling the Crystallization of Deposited Amorphous Si by Ion-implantation. Simon Ruffell1, David J. Sprouster1, Andrew P. Knights2 and Jim S. Williams1; 1Research School of Physics and Engineering, Australian National University, Canberra, Australian Capital Territory, Australia; 2Department of Engineering Physics, McMaster University, Hamilton, Ontario, Canada.

High quality polycrystalline Si (poly-Si) is desirable for a range of large area electronics including thin film transistor based devices, and thin film solar cells. One method of forming thin film poly-Si is by the crystallization of deposited amorphous Si (a-Si). A substantial research investment has been directed towards crystallization strategies that result in poly-Si comprised of large, high quality grains for high carrier mobility and lifetime. In this study we investigate ion-beam processing of PECVD deposited a-Si films to control the final poly-Si film microstructure following thermal processing. As-deposited films were implanted with keV Si ions with fluences varying from 10^14 to 10^17 cm-2. The crystallization kinetics of these films has been studied by X-ray diffraction, optical and Raman spectroscopy over annealing temperatures ranging from 600 to 700 °C. The resultant poly-Si has been characterized by cross-sectional transmission electron microscopy and electron backscattering diffraction. These measurements have been correlated with Hall carrier transport and resistivity measurements. Compared to the as-deposited a-Si, the implanted a-Si requires longer annealing times to crystallize. For example, at 625 °C the unimplanted film crystallizes in approximately 5 minutes compared to several hours for the implanted films. We attribute this to the removal of nucleation sites during implantation, that seed solid phase crystallization, in the as-deposited films. Furthermore, the nucleation time of crystallites in the implanted films increases with decreasing implant fluence. To help understand the nucleation issues for deposited a-Si, nanoindentation of ion-implanted a-Si, which is known to seed subsequent crystallization, is used for comparison. Ion beam-induced strain in the as-implanted films may be responsible for these changes in the annealing properties. The changes in H content, bonding, and depth profiles, by implantation are also investigated. The increased nucleation rate results in poly-Si composed of smaller grains in the highest fluence implants. The resistivity correspondingly decreases with increasing grain size. This novel ion-beam processing step opens up opportunities for control of the electrical and optical properties of the poly-Si as well as a method of selected area crystallization. It is expected that an ion-implant step following deposition will reduce the sensitivity of the poly-Si properties on the initial deposition process parameters.


11:45 AM II5.5
Molecular Dynamics Study of Initial Morphology Evolution of Amorphous Carbon by Glancing Angle Deposition. Minwoong Joe, Myoung-Woon Moon and Kwang-Ryeol Lee; Korea Institue of Science and Technology, Seoul, Korea, Republic of.

The initial evolution of surface morphology of amorphous carbon grown at different incidence angles (0°-70°), but at a fixed energy (75 eV) has been investigated through classical molecular dynamics simulation with a many-body reactive potential suggested by Brenner. At normal or near-normal incidence films are developed in layer-by-layer mode, so smooth surfaces are found in every stages of the deposition process. At a glancing incidence, however, the surface become rougher and exhibit inhomogeneous growth mode: the growth in the illuminated side of initial seed structure is predominant compared with the shadowed side from its initial stage of the growth. As the incidence angles increase, clear anisotropy of impact-induced rearrangements of atoms is found by calculating total atomic average displacement vector. Its implication on the origin of surface smoothening and roughening is discussed.


 

SESSION II6: Implantation and Nanostructures II
Chair: Naoki Kishimoto

Wednesday Afternoon, April 27, 2011
Room 3016 (Moscone West)


1:30 PM *II6.1
Amorphization of Ion-irradiated Nano- and Micro-crystalline SiC. Weilin Jiang, Pacific Northwest National Laboratory, Richland, Washington.

Silicon carbide (SiC) possesses outstanding physical and chemical properties that make it a prominent candidate material for a variety of applications. These include high-temperature, high-power and high-frequency electronic and optoelectronic devices, structural component for fusion reactors, cladding material for gas-cooled fission reactors, and an inert matrix for transmutation of plutonium and other transuranics. Extensive experimental and theoretical research efforts have been devoted to the study of irradiation effects in SiC single crystals over the past decades. As a result, a significantly improved understanding of the disordering processes in bulk SiC has been achieved. Materials containing a large area of surfaces and interfaces are of both scientific and technological importance. During irradiation, interface can act as either a defect sink for crystallization or a source for amorphization, depending on interfacial properties and experimental conditions. Radiation-resistant materials are constantly sought for a rational design of future nuclear energy systems, while radiation-susceptive materials have attracted a significant attention in the area of radiation detection and monitoring. Recently, we have initiated a study of disordering behavior of nanostructured 3C-SiC irradiated with MeV Au2+ [W. Jiang, et al, Phys. Rev. B 80, 161301(R) (2009)] and Si+ ions [W. Jiang, et al, J. Mater. Res., 2010, in press] and have compared it to its single-crystal counterpart. The primary methods for material characterization have included ion channeling, x-ray diffraction, and transmission electron microscopy. While the Au2+ irradiation suggests that the amorphization dose for the nanocrystalline 3C-SiC is not higher than for its bulk material at room temperature, the results from the Si+ irradiation indicate preferential amorphization at the interfaces. Further experiments for nanocrystalline 3C-SiC at temperatures close to and higher than the critical temperature for amorphization of single crystal 3C-SiC are currently undertaken and the results will be presented and discussed. The Environmental Molecular Sciences Laboratory at the Pacific Northwest National Laboratory has recently acquired a Helium Ion Microscope (HIM), which provides us an opportunity to study the microstructural transformation at the surface and interface. The HIM capability is unique in this study because it not only provides ion irradiation with a well controlled He+ ion fluence and flux at a selected irradiation spot, but also makes it possible to examine phase transformation in situ at surfaces and interfaces with a high-resolution (~0.3 nm). Amorphization at the surfaces and interfaces of SiC powders, sintered samples and polycrystalline films is now being studied using HIM. Complementary XRD and TEM also will be performed. The results will be presented and discussed in the presentation.


2:00 PM II6.2
Application of Ion Beams Technology in Photonics: A Short Review. Ke-Ming Wang, School of Physics, Shandong University, Jinan, Shandong, China.

Ion implantation has been successfully used in semiconductor industry. It can improve the metal’s surface hardening significantly. Also ion implantation can modify the optical properties of insulator. It can induce the change of the refractive index in oxide crystals. This short review covers (1)Optical waveguides in oxide crystal by ion implantation. MeV lighter ions (He or H)) with higher fluence (around 1016 ions/cm2) have been used to form optical waveguides in a series of oxide crystals. Recently MeV heavier ions (compared to He or H)) with lower fluence (around 1014 ions/cm2) can induce positive changes of refractive index in the guiding region in some oxide crystals. Planar and channel waveguides in oxide crystal have been fabricated with lithography. These crystals include nonlinear crystals, laser crystal as well as photorefractive crystals. (2)Crystal ion slicing. It is a novel approach to ion-mediated epitaxial liftoff for oxide crystals. Crystal ion slicing can produce high-quality, single-crystal metal-oxide films for a wide range of optical materials. It is very useful in photonic crystal slabs. (3)Focused ion beam (FIB). Photonic crystals are composed of periodic dielectric nanostructures. FIB has become an important technology for a wide array of materials science applications, especially in photonic crystal slabs.


2:15 PM II6.3
Nanoimplantation and In-situ Ion Irradiation at Sandia National Laboratory. Khalid Hattar, Edward Bielejec, George Vizkelethy and Barney Doyle; Radiation Solid Interaction, Sandia National Laboratories, Albuquerque, New Mexico.

This presentation will highlight several of the recent capabilities that have been developed at the new ion beam laboratory user facility at Sandia National Laboratories for the manipulation of materials at the nanometer to centimeter scale using energetic ion beams. This facility contains four ion accelerators that can irradiate a breadth of ion species over energies range from 1 keV to 100 MeV and spot sizes ranging from 10 nm2 to 1 cm2. Of the greater than 20 ion beam lines with various end stations, two will be highlighted and the capabilities for nanostructured material modification and understanding of the fundamental physics active in irradiated nanoscale volumes will be discussed. The design and capabilities of a new 100 keV mass separated-focused ion beam with 10 nm resolution, four low-current electrical micromanipulators, and a gas injection system will be detailed. The 10 nm resolution at 100 keV, the mass-separation capabilities of gold silicon eutectic system, and the gallium-69 and gallium-71 isotopes will be demonstrated. In addition, the planned use and the initial experimental results utilizing the system for controlled single ion implantation for quantum computing devices and the development of confined volume deformation studies through the creation of tailored dislocation cell wall structures will be highlighted. In addition, a new high contrast, high tilt transmission electron microscopy (TEM) will also be discussed that has been designated as an in-situ ion irradiation TEM. The development plan for this facility will be outlined including: ion optics calculations, Monte Carlo simulations of ion species interactions with the thin films, and current construction status of the multiple beamlines envisioned for both light and heavy ion species. The first generation of this in-situ ion irradiation TEM will introduce ion beams from a 6 MeV Tandem accelerator at an angle nearly perpendicular to the electron beam permitting direct observation of cascade tracks produced during implantation. This discussion will also include a description of the multiple TEM stages that have been purchased or developed for this microscope including stages for the tomography of ion tracks, the mixing and heating of two liquid stages, and the exposure to a vapor-phase at elevated temperature. Finally, the potential applications for this new in-situ ion irradiation TEM for experiments ranging from radiation hard electronics to radiation tolerant cladding materials will be discussed. This work is partially supported by the Division of Materials Science and Engineering, Office of Basic Energy Sciences, U.S. Department of Energy both at Sandia and under grant DE-FG02-07ER46443. Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin company, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.


2:30 PM II6.4
Effect of Irradiation Induced Defects on Forming and Resistive Switching Response of NiO Thin Films. Tae-hyun Kim, Muhammad Saleh, Dinesh Venkatachalam, Kidane Belay and Robert Elliman; Department of Electronic Materials Engineering, The Australian National University, Canberra, Australian Capital Territory, Australia.

Resistive switching random access memory (RRAM) using transition metal oxides are regarded as potential candidates for Flash replacement due to the expected scaling potential. NiO is known to exhibit excellent resistive switching characteristics, including high-speed, low power switching and CMOS compatibility. Resistive switching in this case is thought to be based on a thermochemical process in which a conductive filament formed by field-induced defects is broken by defect annealing caused by local Joule heating. An understanding of the defects responsible for switching and their thermal annealing characteristics are critical for modeling such behavior. In this study, we examine the effect of defects created by high-energy Si ion-implantation on the forming and resistive switching response of NiO thin films. Polycrystalline NiO films were grown on Pt(200nm)/Ti(15nm)/SiO2(300nm)/Si substrates by dc magnetron sputtering and subsequently irradiated with 80 keV O ions, 270 keV Ni ions, and 2.0 MeV Si ions to various fluences. The forming voltage was found to decrease with increasing ion fluence due to the presence of irradiation-induced defects, and to recover during subsequent thermal annealing as the defects were removed. The implications of these results are discussed in terms of the thermochemical model of switching.


2:45 PM II6.5
Pseudo-crystals of Quantum Dots by MeV Ion Beam. Daryush Ila1, Robert L. Zimmerman1, Claudiu I. Muntele1 and S. Budak2; 1Physics, Alabama A&M University, Normal, Alabama; 2Electrical Engineering, Alabama A&M University, Normal, Alabama.

For the past fifteen years, we have formed nanostructure in the MeV ion beam track in order to fabricate pseudo-crystals consisting of nanostructures. The focus of our work is based on the energy deposited due to ionization in order to produce quantum dots or nano-structures resulting to production of pseudo-crystal consisting of nano-crystals with applications in optical devices as well as with applications in highly efficient thermoelectric Materials. The interacting nanocrystals enhance the electrical conductivity, reduce thermal conductivity and increase the Seebeck coefficient, in order to produce highly efficient thermoelectric materials. Theoretically, the regimented quantum dot superlattice/ pseudo-crystals consisting of nanostructures of any materials produces new physical properties such as new electrical band structure, phonon mini-bands, as well as improved mechanical. A proper choice of nanocrystals, host and buffer layer result in production of highly efficient thermoelectric generator (TEG)* with efficiencies as high as 30% which correspond to figure of merit above 4.0. In addition to above such systems are in a unique position to be used both as electrical generation from heat and/or other forms of radiation as well as cooling the structures, thus enhance the applicability of hybrid systems. The interaction of nanostructures results in phonon mini-bands formation reducing the thermal conductivity, while increasing the electrical conductivity resulted in synthesis of TEG with much higher efficiency than reported to this date. We will review a series of materials selected for investigation some operating at temperatures around 300K and some at about 1000K. Sponsors: Supported in part by NASA award number NAG8-1933 and by National Science Foundation under Grant No. EPS-0814103. * Patented


3:30 PM II6.6
Ion Irradiation on Phase Change Materials. Emanuele Rimini1, Egidio Carria2,3, Antonio Massimiliano Mio2, Maria Miritello3, Santo Gibilisco2,3, Corrado Bongiorno1, Giuseppe D'Arrigo1 and Maria Grazia Grimaldi2,3; 1IMM-CNR, Catania, Italy; 2Dipartimento di Fisica e Astronomia, Università di Catania, Catania, Italy; 3MATIS-IMM-CNR, Catania, Italy.

Phase-Change Materials (PCMs), mainly represented by GeTe-Sb2Te3 alloys, are largely used for high-density data storage in optical media (CD-RW, DVD-RAM, DVD-RW, Blu-ray Disc) and as a good candidate in solid-state memory technology (Phase-Change Random Access Memories, PCRAM). The working principle of these devices is based on the change in optical and electronic properties of the chalcogenide alloy, observed during the switch from the amorphous to the crystalline phase, or vice versa. Two states are distinguishable by the pronounced difference in reflectivity (up to 30%) and resistivity (some order of magnitude) observed between these two phases. Ion implantation is a powerful tool to modify the properties of chalcogenide alloys allowing the tuning of the crystallization temperature. We have investigated the effect of ion irradiation on the stability and on the local order of amorphous Ge2Sb2Te5 (GST) and GeTe thin films. The samples, 50 nm thick, were prepared by rf sputtering deposition at room temperature over oxidized Si wafers. Ion irradiation was performed with 130 keV Ge+ at several fluencies in the range 1013-1014 ions/cm2 avoiding any appreciable change in the stoichiometry of the sample. We have reported, by time resolved reflectivity measurements, a faster crystallization kinetic in irradiated samples with respect to the as deposited film. This statement is also confirmed by Transmission Electron Microscopy (TEM) analyses. The structure of GST and GeTe, as determined by Raman spectroscopy, shows interesting alterations after irradiation and the formation of an intermediate structural order, induced by thermal spike effects. The change in the local order justifies the faster crystallization kinetic in irradiated samples. Ion irradiation was also used to dope, by recoil implantation, the chalcogenide layers. A thin SiO2 cap layer (10nm thick) was deposited on the GST film (20nm thick) and then ion implantation of 40keV Ge+ ions at several fluencies in the range 1013-1015 was performed. The Si and O recoiled atoms are able to dope the chalcogenide layer and then a high enhancement of the thermal stability of the amorphous phase was measured (15°C higher crystallization temperature). This feature is of interest for applications in which high-temperature data retention is required. By using Electron Beam Lithography (EBL) masks, ion irradiation has been adopted to re-amorphize crystalline chalcogenide thin layers, selectively, in nanometric regions. This scenario is often observed in the active region of many PCRAM-devices. We have studied the recrystallization of cylindrical amorphous nano-structures (less than 100 nm in diameter) patterned on a 20 nm thick GST film and amorphized by 1014 Ge+ ions at 40 keV. By in situ TEM we have obtained informations, at different temperature, on the stability of these nano-amorphous structures, related to the data retention in PCRAM-devices, and on the crystallization mechanisms.


3:45 PM II6.7
Formation of Embedded Gold Nanoclusters and Nanocluster-cavity Pairs in SrTiO3 Single Crystals. Vaithiyalingam Shutthanandan1, Bruce Arey1, Chongmin Wang1, Ponnusamy Nachimuthu1, Grace Newhouse1, Suntharampillai Thevuthasan1 and Gerd Duscher2; 1EMSL, Pacific Northwest National Lab, Richland, Washington; 2Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina.

Metal nanoclusters on dielectric surfaces sometimes lead to unique physical and chemical properties. In most cases, an atomic scale understanding of the interactions between metal clusters and oxide surfaces has not been established. In addition, at high temperatures these clusters agglomerate and thus reduced the nano effect. Hence, embedded nanoclusters (at the surface region) to reduce these agglomerations attracts lots of attentions in recent years. In this work, we successfully show that using MeV ion implantation at moderate temperatures, embedded gold nanoclusters can be formed at the SrTiO3 (100) surfaces. We have used a suite of imaging capabilities including newly developed Helium ion microscopy (HIM) and scanning transmission electron microscopy (STEM) with high-angle-annular-dark-field (HAADF) imaging to understand the structural properties and spatial distribution of the Au clusters. The results indicate that gold nanoclusters were formed uniformly throughout the implanted region. Small nanoclusters within larger clusters were formed at 200°C and 300°C implantations. Size of the nanoclusters ranges from 5 to 30 nanometers. On the other hand, when the gold ions were implanted at high temperatures (700°C), nanocluster-vacancy pairs were formed uniformly throughout the implanted region. In cluster free regions where the Au concentration is low, the HADDF results clearly indicate the substitution of Au for cations. The Au clusters and the cavity show spatial association, indicating a strong interaction during their respective clustering process.


4:00 PM II6.8
Shaping of Au and Ge Nanoparticles by Irradiation with Swift Heavy Ions. Karl-Heinz Heinig, Bernd Schmidt, Arndt Muecklich and Chavkat Akhmadaliev; Inst. Ion Beam Physics & Materials Res., Research Center Dresden-Rossendorf, Dresden, Germany.

The driving forces of nanomaterials processing by swift heavy ions as identified by our studies are (i) the materials dependent electronic stopping power, (ii) the volume change upon melting as well as (iii) far-from-equilibrium steady-state solubilities and strongly anisotropic diffusion coefficients. Size distributions, shapes and anisotropies of nanoparticles can be tailored by appropriate tuning of these driving forces. The evolution of Au and Ge nanospheres under swift heavy ion irradiation was studied experimentally and by atomistic computer simulations. Au nanospheres of 15 nm di-ameter elongate to rods, whereas Ge nanospheres become flat. Surprisingly, this shaping as well as the quantitative dependence on experimental conditions can be described completely with classical thermodynamics, which will be demonstrated by our atomistic computer simulation studies: For instance, the ratio (rod length)/(initial sphere diameter) increases with the square root of the ion fluence, and the speed of the elongation follows the law of Hagen-Poiseuille. Of special interest is the nanostructure evolution when en-ergy deposition into the nanoparticle suffice melting only for central tracks. This rare event for broad size distributions can be seen, e.g., in Phys.Rev. B78(2008)054102. Us-ing unimodal size distributions and changing the ion direction during irradiation, tailor-ing of very exotic nanoparticle shapes become feasible.


4:15 PM II6.9
Effects of Hydrogen Ion Implantation and Thermal Annealing on Structural and Optical Properties of Single-crystal Sapphire. William Spratt1, Chuanlei Jia2, Lei Wang3, Vimal K. Kamineni1, Colin McDonough1, Paul Shreeman1, Mengbing Huang1, Richard Matyi1, Alain C. Diebold1, Robert Geer1 and Hua Xia4; 1CNSE, Univeristy at Albany, Albany, New York; 2College of Physics Science and Technology, China University of Petroleum, Dongying, Shandong, China; 3School of Physics and Microelectronics, Shandong University, Jinan, Shandong, China; 4RF and Photonics Laboratory, General Electric Global Research Center, Niskayuna, New York.

Due to its outstanding thermal and chemical stability, single-crystal sapphire is a crucial material for high-temperature optical sensing applications. This work explores the use of hydrogen ion implantation for the fabrication of thermally stable optical waveguides in sapphire crystals. Sapphire wafers of c- and m-plane orientations were implanted with hydrogen ions of 35 keV and 1 MeV to doses of 10^16-10^17/cm^2. Post-implantation annealing was conducted between 500 and 1600 °C in air. A variety of analytic techniques were used to characterize the samples, including nuclear reaction analysis for measuring the depth distribution of hydrogen, Rutherford backscattering/ion channeling for examining crystal defects, and x-ray diffraction and Raman scattering for detecting strain and stress developed in the crystal. The optical constants were determined using spectroscopic ellipsometry and prism coupling experiments. Optical waveguiding effects showing the existence of several guided modes in H-implanted (1 MeV, 1x10^17/cm^2 ) sapphire wafers were significantly enhanced by annealing at temperatures > 800 °C, and remained strong even after annealing at 1600 °C. H ion implantation and thermal annealing could result in a decrease up to ~ 1% in the refractive index of sapphire. The optical characteristics were found to correlate with the structural information of H desorption, lattice disorder, and crystal strains. We discuss the implications of these findings in relation to ion beam fabrication of optical waveguides in sapphire crystals for high-temperature sensing applications, particularly the role of H related microdefects (e.g., nanocavities/nanovoids) in tailoring the refractive index of single-crystal sapphire.


4:30 PM II6.10
Optical Bistability in Thermochromic Ion Beam Synthesized Vanadium Dioxide Nanoclusters. Helmut Karl and Bernd Stritzker; University of Augsburg, Augsburg, Germany.

VO2 shows a metal-insulator transition at 68°C which is characterized by an extreme change in its electrical resistivity and optical properties in the near infrared spectral region. Nanocomposites consisting of VO2 nanocrystals embedded in SiO2 thin films allow to control the semiconducting and metallic domains which have strong influence on the dynamics of the metal-insulator transition. Thin films of those nanocomposites are very promising materials for application in active optical waveguides and photonic crystals. The unique properties of ion implantation (e.g. generation of supersaturated impurity concentrations) allow chemical phase selective synthesis of vanadium oxides in SiO2 and other optically transparent host materials and is predestined to fabricate planer two-dimensional arrays of buried VO2 nanocrystals. In this work nanocrystalline precipitates of vanadium dioxide embedded in fused silica and thermally grown SiO2 on silicon have been selectively synthesized by sequential ion implantation of the elements V and O followed by a rapid thermal annealing step. In this way nanocrystalline VO2 ensembles with a narrow size distribution (sub-100nm) have been produced. The control of nanoparticle size and location was achieved by the implanted fluence and energy under otherwise identical synthesis conditions. The densely packed VO2 nanocrystallites show a wide temperature hysteresis extending the metal-insulator bistability down to room temperature and above that of bulk material. We were able to tailor the hysteresis by generation of reversible point defects by He and Ar irradiation avoiding at the same time electronic doping. The generated point defects determine strongly the thermodynamic domain stability in these nanomaterials. These findings allow engineering of these effects in VO2 nanocomposite planar optical waveguide and grid structures for application in optical memory and switching devices. First results of VO2 nanocomposite planar optically active grid structures will be presented.


4:45 PM II6.11
Raman Scattering Study of Si Nanoclusters Formed in Si through a Double Au Implantation. Gayatri Sahu and Durga P. Mahapatra; Institute of Physics, Bhubaneswar, India.

Silicon is an excellent material for electronics but because of its indirect band gap, it is an inefficient light emitter. This hinders the use of Si in optoelectronic applications. However, now it has been established that at nanoscale there is efficient light emission even at room temperatures. This opens up the possibility of the use of Si in integrated optoelectronic devices. Among many processing methods, ion implantation is one of the most used techniques in Si processing. This technique, with precise control of ion energy and fluence, has been used earlier to prepare Si nanoclusters (NCs) in SiO2 through Si implantation. Unlike that in the present study, we have adopted a novel two stage Au implantation + irradiation technique to synthesize Si NCs in bulk Si. In this study 32 keV Au- ions with fluence in the range of 5 x 1015 - 1 x 1017 ions-cm-2 were implanted in Si(100) samples (n-type, resistivity ~ 1-20 Ω-cm) resulting in amorphization of a surface layer around 30 nm thick. The samples were further irradiated with 1.5 MeV Au+ ions to a fixed fluence of 1 x 1015 ions-cm-2 with an aim of obtaining Si NCs in the amorphized matrix through the MeV Au irradiation induced localized recrystallization. Raman Scattering measurements carried out following the low energy Au implantation, at an excitation wavelength of 514.5 nm, showed a Stokes line at 521 cm-1, characteristics of crystalline Si. This Stokes line comes from Raman scattering in the underlying Si lattice. Its intensity is found to drop with increase in damage production and amorphization in the over layer due to increase in implanted ion fluence. The subsequent Au irradiation at 1.5 MeV is found to result in Si NC formation in the amorphized layer as identified from a Stokes line below 521 cm-1. However, the spectra could not be fitted to simulated results obtained using a phonon confinement model based on the average size for the NCs. This was mainly due to defects and strain present in the NCs. A subsequent 1 h annealing at a temperatures between 500o to 950o C resulted in better spectra that could be nicely correlated with the mean size of NCs which is found to grow from about 2nm to higher values with increase in annealing temperature. Results will be presented and discussed.


 

SESSION II7: Poster Session
Chair: Daryush ILA

Wednesday Evening, April 27, 2011
8:00 PM
Salons 7-9 (Marriott)


II7.1
Adhesion Reduction of Glassy Polymeric Carbon by Ion Implantation. Cydale Smith, Tabitha Lewis, Claudiu Munetle and Daryush Ila; Center for the Irradation Of Materials, Alabama A&M University, Normal, Alabama.

Glassy Polymeric Carbon is used in a variety of application due to its thermal stability, chemical inertness and its biocompatibility. GPC is a material of choice for artificial heart valves. But, once installed in the body cells begin to attach to the heart valve thus making the operation of the valve impaired. One solution of the cell attachment problem is to bombard the surface of the GPC with low energy Ag ion bombardment. Preliminary studies have shown that this technique is successful. But, it is uncertain the true cause for the reduction in adhesion on the GPC surface. In order to clarify the mechanism we bombarded separate GPC samples with Ag and C ions at various ion fluences. Contact angle measurements was performed on all samples and compared as function of ion and ion fluence. We also used high resolution RBS and Raman spectroscopy for process and sample characterization. Details will be discussed during the meeting.


II7.2
Characterization of Properties and Microstructure of Glassy Polymeric Carbon Following Ag Ion Irradiation. Malek A. Abunaemeh1,2, Mohameh Seif3, Daryush Ila1,2, Abdalla Elsamadicy4 and Claudiu Muntele1; 1Center for irradiation of materials, Alabama A&M University, Normal, Alabama; 2Physics, Alabama A&M University, Normal, Alabama; 3Mechanical Engineering, Alabama A&M University, Normal, Alabama; 4Physics, University of Alabama in Huntsville, Huntsville, Alabama.

The TRISO fuel has been used in some of the Generation IV nuclear reactor designs. It consists of a fuel kernel of UOx coated in several layers of materials with different functions. Pyrolytic carbon (PyC) is one of these layers. In this study we investigate the possibility of using Glassy Polymeric Carbon (GPC) as an alternative to PyC. GPC is used for artificial heart valves, heat-exchangers, and other high-tech products developed for the space and medical industries. This lightweight material can maintain dimensional and chemical stability in adverse environment and very high temperatures (up to 3000C). In this work, we are comparing the changes in physical and microstructure properties of GPC after exposure to irradiation fluence of 5 o MeV Ag equivalent to a 1displacment per atom (DPA) at samples prepared at 1000, 1500 and 2000C. For surface analysis we are using Raman spectroscopy and transmission electron spectroscopy along with mechanical microstructure characterization. The GPC material is manufactured and tested at the Center for Irradiation Materials (CIM) at Alabama A&M University.


II7.3
Ga+ Focused-ion-beam Implantation Induced Masking for H2 Etching of ZnO Films. Hsin-Chiao Fang, Jun-Han Huang, Wen-Huei Chu and Chuan-Pu Liu; Department of Materials Science and Engineering, National Cheng Kung University, Tainan, Taiwan.

A new resist-free etch stop technique has emerged and focused on Si that utilizes preferential etching behavior with Ga+ ion implantation in an focused ion beam (FIB), where the Ga+ ion implanted regions are etched either physically or chemically at a much slower rate than the unimplanted regions. In this study, gallium implantation of ZnO by focused ion beam is used to create a mask for ZnO dry etching with hydrogen. Effects of Ga+ fluence on the etch-stop properties and the associated mechanisms are investigated. The fluence of 2.8x10^16 cm-2 is determined to be optimum to render the best mask quality. While lower fluences would cause less etching selectivity, higher fluences would cause erosion of the surface and particles to be precipitated on the surface after H2 treatment at high temperature. In contrast to the commonly adopted gallium oxide formation on Si, transmission electron microscopy (TEM) analysis reveals that, for the fluences 2.8x10^16 cm-2, Ga+ ions are incorporated as dopants into ZnO without any second phases or precipitates, indicating the Ga-doped ZnO layer behaves as a mask for H2 etching due to the higher electronegativity of Ga+ toward oxygen. However, for the fluences 4.6x10^16 cm-2, the surface particles are responsible for the etch stop, and are identified as ZnGa2O4. We finally demonstrate a complicated pattern of “NCKU” on ZnO by using this technique. The study not only helps clarify the related mechanisms, but also suggests a feasible extension of the etch-stop process that can be applied to more functional material.


II7.4
Nano-scale Bending by Focused Ion Beam. Masaaki Otsu, Seigo Sakai, Takafumi Onizuka, Mitsuhiro Matsuda and Kazuki Takashima; Materials Science and Engineering, Kumamoto University, Kumamoto, Japan.

Recently, application of MEMS devices is expanding. More reduction of device size should be needed for improving device performance and multi-functionalization. Manufacturing technology for not only two-dimensional but also three-dimensional structures is required for more device size reduction. Conventional fabrication methods of those devices are, however, based on wafer processing such as lithography, LIGA and so on, it is difficult to manufacture large aspect ratio three-dimensional structure. To make large aspect ratio structures, it is considerable to be easy by bending a part of small aspect ratio structure plastically. In this study, focused ion beam was employed and nano-scale bending method for making large aspect ratio three-dimensional structure was developed. Although focused ion beam is usually used for not plastic forming but nano-scale machining or ion doping, it is used for bending of nano-sized rod plastically. Single crystalline silicon rod with a diameter of less than 300 nm and diamond like carbon rod with a diameter of about 300 nm, which is fabricated using deposition function of the focused ion beam equipment, were used for specimens. Gallium ion beam was irradiated on the specimen perpendicular to the longitudinal direction of the rods. The acceleration voltage of focused ion beam equipment was 30 keV, the beam current was 1 pA or 10 pA, and irradiation time was changed. After gallium ion beam irradiation, bending angle of specimen was measured. Bending forward gallium ion beam source was observed in both materials. Bending angle was in proportion to the irradiation time. Bending angle of single crystalline silicon was larger than that of diamond like carbon. When the diameter of specimen was larger, bending angle was smaller. When the beam current was larger, bending angle was also larger. From the experimental results, equation for estimation of bending angle was suggested.


II7.5
Determination of Ultra-shallow Disorder Profiles in Si Using Ellipsometry. Istvan Mohacsi1,3, Peter Petrik1, Miklos Fried1, Jaap A. van den Berg2, Michael A. Reading2, Andrea Parisini5, Mario Barozzi4, Evgeny Demenev4 and Damiano Giubertoni4; 1MTA-MFA, Budapest, Hungary; 2Institute for Materials Research, University of Salford, Salford, Salford, United Kingdom; 3Eotvos Lorand University, Budapest, Hungary; 4MiNALab, Center for Materials and Microsystems-Irst, Fondazione Bruno Kessler, Trento, Italy; 5CNR-IMM Sezione Bologna, Bologna, Italy.

Ultra-shallow (below 20 nm) disorder profiles due to As, Si, and BF2 implants into single-crystalline Si (c-Si), were characterized by spectroscopic ellipsometry (SE). The shallow profiles have been prepared by implantation of As, Si, and BF2 at energies between 0.2 keV and 10.0 keV in single crystalline Si. The aim of the investigations was to test the sensitivity and precision of the optical determination of the disorder profile. The results were verified using the complementary techniques of medium energy ion scattering (MEIS), transmission electron microscopy (TEM), and secondary ion mass spectrometry (SIMS). For the ellipsometric investigation the implanted depth region was divided into sublayers with dielectric functions calculated by the effective medium approximation using single-crystalline and disordered components. The depth profile was described using a range of methods including a box model, an independent multilayer model, a graded multilayer model, an error function, and Gaussian profiles. Literature values [M. Fried et al., J. Appl. Phys. 71, 5260 (1992)] and Tauc-Lorentz (TL) parametrizations [Jellison et al., Appl. Phys. Lett. 69, 371 (1996)] as well as multi-sample and conventional single-sample approaches have been compared to describe the dielectric function of the disorder component. We found good agreement between the depth profiles obtained by the different methods. There is an offset between the SE and MEIS profiles due to the fact that SE is sensitive to the surface roughness and to a possible change of the refractive index of the surface oxide due to the high-fluence implantation. The correlation between this offset and the surface roughness has been investigated using atomic force microscopy. The TL parameters of the disordered component depend on the parameters of the ion implantation for all the As-, Si-, and BF2-implanted samples. The fact that (in terms of TL parameters) the Si-implanted case is similar to the As- and BF2-implanted cases shows that this behavior is not due to the build-up of a separate phases as a result of the high As concentration in the high-fluence shallow implants. In case of the annealed samples the models become more complicated and the build-up of these phases cannot be ruled out. In spite of this, the damage depth and kinetics determined by SE agree well with that determined by the reference methods. [This work has been supported by the European Commission - Research Infrastructure Action under the FP6-Program contract no.026134 (RII3) ANNA and the Hungarian NKTH ICMET07 project.]


II7.6
Swift Heavy Ion Irradiation Effect on Ag Doped CdS Embedded in PMMA. Shweta Agrawal, Vipin Jain and Y. K. Vijay; Physics, University of Rajasthan, Jaipur, Rajasthan, India.

Semiconductor nanocrystals (NCs) have received much interest for their optical and electronic properties. When these NCs dispersed in polymer matrix, brightness of the light emission is enhanced due to their quantum dot size. Silver doped cadmium sulphide NCs were synthesized through chemical route method with an average size of 5-8nm range. The impurity of Ag in CdS (CdAgS) is responsible for the additional defects which may tune the optical and structural properties in comparison to the pure CdS NCs. The synthesized NCs are characterized by XRD, XRF, SEM, and TEM. The effect of Ag doping and Swift heavy ion irradiation on optical properties of nanocomposite films is analysed by PL and UV measurements. The XRD results show that Ag doped CdS was grown in the hexagonal phase of about 10nm size as calculated by Scherer formula, which have good agreement with TEM measurements. The presence of silver in CdS nanoparticles is characterized by X-Ray fluorescence. These NCs were dispersed in PMMA matrix by solution cast method and irradiated by swift heavy ion (SHI) (100MeV, Ni+7 ion beam). The UV-Vis measurement show a red shift in optical absorption and band gap decreases after irradiation with respect to pristine CdAgS nanocomposite polymer film. Photoluminescence shows the enhancement in luminescence intensity after irradiation.


II7.7
RBS, XRD, Raman and AFM Studies of Microwave Synthesized Ge Nanocrystals. N. Srinivasa Rao, Anand p. Pathak, G. Devaraju, V. Saikiran and SVS Nageswara Rao; School of Physics, University of Hyderabad, Hyderabad, A P, India.

Ge nanocrystals embedded in silica matrix have been synthesized on Si substrate by co-sputtering of SiO2 and Ge using RF magnetron sputtering technique. The as-deposited films were subjected to microwave annealing at 800 and 9000C. Rutherford backscattering spectrometry (RBS) has been used to measure the Ge composition and film thickness. The structural characterization was performed by using X-ray diffraction (XRD) and Raman spectrometry. XRD measurements confirmed the formation of Ge nanocrystals. Raman scattering spectra showed a peak of Ge-Ge vibrational mode around 299 cm−1, which was caused by quantum confinement of phonons in the Ge nanocrystals. Surface morphology of the samples was studied by atomic force microscopy (AFM). Variation of nanocrystal size with annealing temperature has been discussed. Advantages of microwave annealing are explained in detail. *Corresponding author E-mail: appsp@uohyd.ernet.in Tel: +91-40-23010181/23134316, Fax: +91-40-23010181 / 23010227.


II7.8
Dot and Ripple Nanopatterns on Ge Surfaces by Normal and Tilted Bombardment with Bi2 and Bi3 Ions. Lothar Bischoff, Karl-Heinz Heinig, Bernd Schmidt, Stefan Facsko and Wolfgang Pilz; Inst. Ion Beam Physics & Materials Res., Research Center Dresden-Rossendorf, Dresden, Germany.

The self-organisation of surface pattern on (001)Ge was investigated after bombardment with different heavy bismuth species of monomers Bi+, Bi++ and clusters Bi2+, Bi3+, Bi4+, and Bi3++, obtained from a Bi-liquid metal ion source [1] in a mass separating 30 kV focused ion beam system. The surface patterns, depending on the angle of ion cluster incidence at ion irradiation differ drastically from the well-known porous or sponge-like nanostructures formed on Ge at monomer ion irradiation so far: the surface remains crystalline as proven by Raman measurements, and the dots and ripples heights were in the order of their wavelengths in contrast to monomer irradiation where an porous surface layer was obtained. The structure formation was investigated in the fluence range from1015 to 1017 ions/cm2 as a function of angle of incidence and energy per atom of the different projectile ions. The high mass of the cluster ions leads to a patterning mechanism different from the Bradley-Harper model, which becomes strikingly apparent by the crystalline Ge surface. An identified threshold of this new patterning mode could help to understand the mechanism: The ion-impact-induced deposition of energy per volume (as estimated by SRIM) must exceed a value which coincides with the energy needed for melting. Thus, Bi segregation during melt pool re-solidification and the 5% volume difference between molten and solid Ge can cause the observed Bi separation and Ge patterning, respectively. A consistent, qualitative model will be discussed. [1] L. Bischoff, W. Pilz, P. Mazarov, and A.D. Wieck, Appl. Phys. A 99 (2010) 145.


II7.9
Modeling of Electron Transport Across Ion Beam Patterned Quasi-quantum Well Nanostructures. John K. Chacha1, Jonathan Lassiter4, Claudiu Muntele2, Satilmis Budak1, Abdallah Elsamadisy4, Kaveh Heidary1 and Daryush Ila3,2; 1Electrical Engineering, Alabama A&M University, Huntsville, Alabama; 2Center for Irradiation of Materials, Alabama A&M University, Normal, Alabama; 3Physics, Alabama A&M University, Normal, Alabama; 4Physics, University of Alabama Huntsville, Huntsville, Alabama.

We use high energy ion beams to modify co-deposited nanolayer films of alternated materials (insulator and metal, semiconductor 1 and semiconductor 2, or more complex mixtures), to form nanodots through localized nucleation. Our particular application is for high efficiency thermoelectric conversion systems. The performance of a thermoelectric converter is generally given by the figure of merit, ZT, which is a function of the Seebeck coefficient, electrical conductivity, and thermal conductivity. A performant device would have a maximized electrical conductivity and a minimized thermal conductivity (maximum electron transport, minimal phonon transport). The current models of electron and phonon transportation through 1D, 2D, 3D quantum regimented structures assume an infinitely repetitive perfect structural “cell”, with complicated algorithms requiring intensive computing power. The main focus for our modeling effort is to reduce the three-dimensional problem to a single dimensional approximation without sacrificing the quality of the result. The nanostructure investigated here has Si quantum dots periodically arranged in the z-direction (cross-plane) while randomly distributed in the x and y directions, with an inter-dot spacing smaller than the cross-plane periodicity. We are using the Non-Equilibrium Green Functions Formalism (NEGF) for calculating the theoretical electrical properties assuming a one-dimensional quantum well arrangement, i. e. electrical continuity in the x-y plane (infinite boundaries). The results are compared with experimental measurements on such structures.


II7.10
Projectile Energy Dependence of Sputtering Yield of Bi Bombarded with keV Ar+. Naresh T. Deoli, Lucas C. Phinney, Jose L. Pacheco and Duncan L. Weathers; Physics, University of North Texas, Denton, Texas.

Sputtering yields of neutral atoms sputtered from the surface of solid Bi by normally incident 10-50 keV Ar+ have been measured. The sputtered atoms were collected on aluminum foils under ultrahigh vacuum conditions, and the collector foils were subsequently analyzed using heavy ion Rutherford backscattering spectroscopy. The collector technique involving accurate current integration was adopted for the determination of angular dependence and projectile energy dependence of the yields. Details of measurements and data analysis are presented.


II7.11
Space Charge Relaxation Processes in Energetic Ion Beam Irradiated Polyetherimide Film. Jitendra K. Quamara and Geetika Goyal; Physics, National Institute of Technology, Kurukshetra, HARYANA, India.

The application of polymeric materials in nuclear and fusion reactors, high energy accelerators, medical and industrial irradiation facilities have generated a considerable interest in investigating the radiation induced effects in polymers. During last couple of decades there have been several reports from NASA on the radiation induced performance aspects of PEI for its application in space. However most of these studies have been carried out with electron and gamma irradiation.. In the present work we are studying the dielectric relaxation behaviour of energetic Ag ion irradiated PEI using thermally stimulated depolarization current (TSDC) technique. The TSD currents were obtained from 100 MeV Ag ion , irradiated polyetherimide samples ( thickness 85 μm ) in the temperature range 30-250C. The TSDC characteristics in general consist of maxima situated around 110, 160, 200 and 230C identified as β-, αβ-, α- and ρ-peaks respectively. In some cases, notably those corresponding to low values of Ep and Tp, an additional shoulder designated as γ has also been observed around 40 C. The number of peaks actually appearing in a particular TSDC spectrum, their locations, heights and sharpness are governed not only by the poling parameters (Ep, Tp), storage time and depolarization parameters, but also by the fluence at which the samples have been Our present investigations show that high-energy ion irradiation of PEI significantly affects its various dielectric relaxation processes. The absence of γ-peak in irradiated PEI has been attributed to the radiation induced damages of ether linkages. The ion irradiation not only results in the demerization of carbonyl groups thereby affecting the β-relaxation but also results in the formation of shallow energy trap centers. A new relaxation process (δ-relaxation) is also observed in the vicinity of β-relaxation in irradiated PEI. The variation in the nature of α-relaxation is associated to the radiation induced cross-linking and crystallinity. The nature of TSDC curves also depend on the nature of ion. Though β-relaxation and the α-relaxation show their appearance in the same temperature region irrespective of the ion, the magnitude and the dominance of the respective relaxation process appears to be dependent on the nature of ion.


II7.12
Comparison of Ion Bbeam and Electron Beam Induced Transport of Hot Carriers in Metal-insulator-metal Junctions. Johannes Hopster1, Detlef Diesing2, Andreas Wucher1 and Marika Schleberger1; 1Faculty of Physics, University of Duisburg-Essen, Duisburg, Germany; 2Faculty of Chemistry, University of Duisburg-Essen, Essen, Germany.

The main dissipation process in the interaction of highly charged ions with metals is electronic excitation. The potential energy of the ions yields electron emission into the vacuum and internal electron emission. To detect the internal hot charge carriers thin [|#12#|]film metal insulator metal junctions (MIM) are used. The measured yield of electron transmission through the insulator barrier depends on the initial excitation energy, the top electrode thickness, the material of the top electrode and the barrier height. By applying a bias voltage between the two metal electrodes energy dispersive measurements are possible. For a deeper understanding of the distribution and transport of the excited electrons in the tunnel junction we investigate comparable processes by irradiation of the tunnel junction with a monoenergetic electron beam. The direct creation of hot charge carriers leads to a tunneling current through the insulator. That can be compared to the ion-induced tunneling yield to deduce the ion-induced electron distribution. Furthermore the electron bombardment gives information about characteristics of the thin [|#12#|]film insulator barrier. When using high electron energies a charging of the barrier by populating oxide traps is possible. Corresponding data that has been obtained on various MIMs will be presented.

II7.13
Transferred to II2.5

II7.14
Growth Behavior of a Single Isolated Anodic Alumina Nanochannel. Shih-Yung Chen1,2, Hsuan-Hao Chan1, Ming-Yu Lai1, Chih-Yi Liu3 and Yuh-Lin Wang1,2; 1Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan; 2Department of Physics, National Taiwan University, Taipei, Taiwan; 3Department of Electro-optical Engineering, National Cheng Kung University, Tainan, Taiwan.

Porous anodic aluminum oxide (AAO) membranes with arrays of nanochannels have been widely used as templates because of their vertically aligned and laterally self-organized arrangements. However, the growth behavior of the AAO nanochannels has not been carefully investigated. In this study, we have developed a method to grow a single isolated anodic alumina nanochannel (SIAAN). The morphology and the cross-section of the SIAAN are characterized by scanning electron microscopy and transmitted electron microscopy, respectively. We found that the growth behavior of the SIAAN is dramatically different from that of the parallel growth of arrayed AAO nanochannels. Such particular growth behavior has been studied in a Monte Carol model and the implications will be detailed discussed.


II7.15
The Dependence of Demolding in Nano-imprinting Process on Atmospheric Pressure CF4 Plasma Treatment. Chiyoung Lee, Hoesup Soh and Jaegab Lee; School of Advanced Materials Egineering, Kookmin university, Seoul, Korea, Republic of.

Soft lithography processes have many techniques: microcontact printing (μCP), replica molding (REM), microtransfer molding (μTM), micromolding in capillaries (MIMIC) and solvent-assisted micromolding (SAMIM). In these techniques, soft mold has many advantages such as nonflat surface patterning capability, easy demolding, and conformal contact with the surface, in addition to simple and easy replication of the mold from the master pattern. However, these techniques have some issues; the minimum residual layer of resin, surface treatment of mold to demolding processes and reliability of patterns. To be demolded mold from substrate, hydrophobic surface of mold was needed. By treating the self-assembled monolayers (SAMs), we could switch the surface more hydrophobic one. Ocatadecyltrichlorosilane (OTS) of which length is about 2nm, has the surface group consisted of CH3 and water contact angle is about 110o on SiO2 surface. Perfluorodeyltrichlorosilane (PFS) of which length is about 1.1nm, has the surface group consisted of CF3 and water contact angle is about 120o on SiO2 surface. These SAMs processes can be separated mold from substrates easily. However these processes are complex and take a long time. CF4 plasma treatments turned the surfaces of the polymeric materials into hydrophobic state by replacing hydrogen atoms with fluorine atoms. In the case of MINS, the water contact angle of MINS surface was about 80o, which was increased to 100o after atmospheric pressure CF4 plasma treatment. XPS analysis confirmed the presence of C-CFn, CF2, CF-CFn, and CF3 which is responsible for the hydrophobic surfaces. The detailed mechanism for the enhanced hydrophobicity will be presented and compared with the conventional surface treatment.


II7.16
Structure and Thermal Annealing of Latent Fission Tracks in Apatite and Zircon. Weixing Li1,2,3, Lumin Wang3,2, Kai Sun2, Maik Lang1, Christina Trautmann4 and Rodney C. Ewing1,2,3; 1Geology Sciences, University of Michigan, Ann Arbor, Michigan; 2Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan; 3Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, Michigan; 4GSI Helmholtz Centre for Heavy Ion Research, Planckstr.1, 64291 Darmstadt, Germany.

The 5~10 nm wide fission fragment tracks, enlarged to several µm by chemical etching, have been widely used for geological dating because the track lengths gradually shorten due to the thermal annealing over geological time. Details of the structure and thermal annealing of the tracks at the atomic-scale have remained elusive, as the original track is destroyed during the chemical enlargement. Our recent direct transmission electron microscopy (TEM) observations of in situ thermal annealing of the "nanoscale" unetched, latent fission tracks provide a bridge between the current empirical models of annealing based on the etched track lengths and a fundamental understanding of the atomic-scale process. Previous to this work, fission tracks in apatite and zircon, the two minerals most often used for fission track dating, were considered to form and anneal in the same way. By combining advanced TEM techniques and thermal annealing at elevated temperatures, we demonstrate that the structure and annealing mechanisms proposed for amorphous tracks, as in zircon, are entirely different from those of the highly porous tracks in apatite. The highly porous tracks produced with 2.2 GeV Au ions in apatite have been directly observed by high resolution TEM. Direct observation shows thermally-induced track fragmentation in apatite, in clear contrast to the amorphous tracks in zircon, which gradually “fade” without fragmentation. Rayleigh instability and the thermal emission of vacancies control the annealing of highly porous fission tracks in apatite. The very different behavior of fission tracks in zircon and apatite is a direct result of differences in the internal structure of the track - the amorphous domain in zircon vs. the low atomic density void in apatite.


II7.17
Parallel Detection and Quantification of Thin-film Peptides with Dynamic-secondary Ion Mass Spectrometry (D-SIMS) Excited by C60+-Ar+ Co-sputtering. Chi-Jen Chang1, Hsun-Yun Chang2, Yun-Wen You2, Wei-Lun Kao1, Guo-Ji Yen1, Meng-Hung Tsai1 and Jing-Jong Shyue1,2; 1Department of Materials Science and Engineering, National Taiwan University, Taipei city, Taiwan; 2Research Center for Applied Sciences, Academia Sinica, Taipei city, Taiwan.

Using pulsed cluster primary ions, time-of-flight secondary ion mass spectrometry (ToF-SIMS) has been shown to be a promising technique for analyzing biological specimens. With molecular fragments of high mass, multiple molecules can be identified at the same time without prior separation. While current reports are based on static-SIMS that makes depth profile more complicate, a dynamic-SIMS based technique is reported in this work. Mixed trehalose and peptides were used as a model for evaluating the parameters that lead to parallel detection and quantification of biomaterials. To suppress the associated carbon deposition with high energy C60+ bombardment, a low energy Ar+ is used to co-ionize the peptide-doped trehalose thin film. Trehalose is mixed with different peptides separately with varied concentrations of peptides. It is found that the normalized intensity of secondary peptide-molecule as respect to trehalose-molecule is direct proportional to its concentration in the matrix. Therefore, by plotting the percentages of peptides exist in trehalose versus their normalized SIMS intensities, calibration curves of each peptide were obtained. Using these curves, it is shown that parallel detection, identification, and quantification of multiple peptides in the matrix can be achieved using ion-beam ionization. This work paves the way of analyzing complicate biological specimens.

II7.18
Transferred to II8.7

II7.19
Transferred to II2.5

II7.20
MeV Si Ions Beam Effects on Thermoelectric Properties of Si/Si+Sb Nanolayered Films. Satilmis Budak1, J. Chacha1, M. Pugh1, Q. Brasfield1, K. C. Taylor1, C. Smith2,3, K. Heidary1, R. B. Johnson3, C. Muntele2 and D. Ila2,3; 1Electrical Engineering, Alabama A.&M. University, NORMAL, Alabama; 2Center for Irradiation of Materials, Alabama A&M University, Normal, Alabama; 3Physics, Alabama A&M University, Normal, Alabama.

Thermoelectric power generators convert thermal gradients to electricity. The efficiency of thermoelectric devices is limited by the properties of n- and p-type (semi)conductors. Effective thermoelectric materials have a low thermal conductivity and a high electrical conductivity. The performance of the thermoelectric materials and devices is shown by a dimensionless figure of merit, ZT = S2σT/k, where S is the Seebeck coefficient, σ is the electrical conductivity, T is the absolute temperature and k is the thermal conductivity. ZT can be increased by increasing S, increasing σ, or decreasing k. We have prepared a thermoelectric device of 100 bilayers (Si/Si+Sb), superlattice films, using ion beam assisted deposition (IBAD). In order to determine the stoichiometry of the elements and the thickness of the grown multi-layer film, Rutherford Backscattering Spectrometry (RBS) and RUMP simulation have been used. The 5 MeV Si ion bombardments have been performed using the AAMU Pelletron ion beam accelerator, to make quantum clusters in the multi-layer superlattice thin films to decrease the cross plane thermal conductivity, increase the cross plane Seebeck coefficient and increase the cross plane electrical conductivity. Keywords: Ion bombardment, thermoelectric properties, multi-nanolayers, Rutherford backscattering, Figure of merit. Acknowledgement Research sponsored by the Center for Irradiation of Materials (CIM), National Science Foundation under NSF-EPSCOR R-II-3 Grant No. EPS-0814103, DOD under Nanotechnology Infrastructure Development for Education and Research through the Army Research Office # W911 NF-08-1-0425.


II7.21
Single Ion Lithography for ZnO Nanowires Growth. Giovani C. Pesenti1, André Luis F. Cauduro1, João W. Oliveira1, Henri I. Boudinov2,1 and Daniel L. Baptista2,1; 1PGMicro, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil; 2Instituto de Física, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil.

The Zinc Oxide (ZnO) is an important wide direct band gap semiconductor and may have direct its electrical properties radically altered by doping. This characteristics make ZnO one of the most promising materials to be applied in the field of nanotechnology, ultraviolet nano-optoelectronic devices and sensors. Due to this, the diameter and the position where ZnO nanowires will be grown must be precisely controlled. Presented here a study of hole formation in Polymethyl methacrylate (PMMA) by single ion lithography, which will be used to growing of ZnO nanowires. PMMA films with thicknesses between 20nm and 200nm were irradiated with Au ions of energy between 1 and 3MeV fluences of 5E8cm-2 and 5E9 cm-2. After the revelation, was deposited a Au film with controlled thickness and then a lift-off process exhibited Au islands on substrate, which served as a catalyst for the growth of ZnO nanowires. The ion energy and PMMA tickness will be related with the nanowire diameters, presented by MEV images. TRIM simulations will be presented also to explain the change of PMMA characteristics during implantion.


 

SESSION II8: Ripples, Topography, Self-assembly
Chair: John Baglin
Thursday Morning, April 28, 2011
Room 3016 (Moscone West)


8:30 AM *II8.1
Ion-implantation for Fabricating, Modifying and Studying Self-assembled Nanostructures. Robert G. Elliman, Dinesh Venkatachalam, Avi Shalav and Taehyun Kim; Electronic Materials Engineering, Australian National University, Canberra, Australian Capital Territory, Australia.

Ion-implantation is a useful tool for fabricating, modifying and studying novel materials and nanostructures, including some that are unique to the ion-implantation process. In this presentation these attributes are illustrated with examples from our recent research. Examples include: a) the formation correlated patterns of Au-precipitates during thermal annealing of Au-implanted Si, a process that is shown to result from compositional banding and convective motion within a thin liquid Au-Si eutectic layer, and b) the use of Er precipitates as a catalyst for growth of luminescent silica nanowires, a process that provides a means of producing complex secondary nanowire structures with potential applications in biological and environmental sensing.


9:00 AM *II8.2
Nanoscale Morphology Evolution Using Ion Beams. Michael J. Aziz, Harvard School of Engineering and Applied Sciences, Cambridge, Massachusetts.

Focused and unfocused ion beam irradiation of a solid changes the surface morphology by sputter erosion, ballistic mass redistribution, and material relaxation processes. Their interplay can result in self-organized nanoscale corrugation, dot, or hole patterns with periodicities down to 7 nm; self-sharpening high-sloped shock fronts that propagate instead of dissipating and evolve to the same slope from a range of initial slopes; and controlled closure of nanopores with applications to single biomolecule detection. Current understanding of these phenomena will be reviewed from an experimental and a theoretical perspective.


9:30 AM *II8.3
Self-organization of Nanopatterns under Ion Irradiation - Atomistic 3D Simulations including Collision Cascades and Thermally Activated Kinetics. Karl-Heinz Heinig, Bartosz Liedke and Wolfhardt Moeller; Inst. Ion Beam Physics & Materials Res., Research Center Dresden-Rossendorf, Dresden, Germany.

The dominating driving force for self-organisation of surface nanopattern during low-energy ion irradiation is still under discussion. Thus, so far continuum models cannot include 3D nonlo-cal processes of ion-solid interactions. On the other hand, till now atomistic simulations could not describe pattern dynamics on the spatiotemporal scale of experiments. Combining collision cascades of ion impacts with continuum equations [1] is one approach to achieve a better understanding of mechanisms, like surface smoothing by an effective ‘downhill’ mass current which are neglected so far [2][3]. Here we present a novel program package, which unifies atomistic 3D simulations of the col-lision cascades with 3D kinetic Monte-Carlo simulations. Atom relocations were calculated with the Binary Collision Approximation (BCA), whereas the thermally activated relaxation of ener-getic atomic configurations as well as diffusive processes were simulated by a very efficient bit-coded kinetic lattice Monte Carlo program. Effects like ballistic mass drift or dependence of lo-cal morphology on sputtering yield are automatically included by this approach. The mechanism of ripple formation induced by local surface currents is studied. The quantita-tive description of current vectors for different environmental parameters, and initial surface condition of sinusoidal structure, can be analized in time and space, following the local atomic drift. Different mechanisms can be distinguished. Without ion irradiation the mass current vec-tors parallel to the surface cause always surface smoothing by Mullins-Herring diffusion. Surface defects created by collsion cascades may inverse the surface mass currents, resulting in self-organization of nanopatterns. Sputtering violates mass conservation of processes mentioned till now. The majority of pub-lished papers assume that sputtering is the dominating driving force for pattern formation. Here it will be shown that ripple patterns perpendicular to oblique ion impacts originate not from the sputtering process but from defect kinetics. Sputtering dominates only formation of ripple pat-terns parallel to the ion beam at grazing incidence. [1] S. A. Norris and M. P. Brenner and M. J. Aziz J. Phys. Condens. Matter 21 (2009) 224017. [2] G. Carter and V. Vishnyakov PRB 54 (1996) 17647. [3] M. Moseler and P. Gumbsch and C. Casiraghi and A. C. Ferrari and J. Robertson Science 309 (2005) 1545.


10:30 AM II8.4
Toward a Quantitative Continuum Model for Ion-Induced Morphology Evolution. Scott Norris1,3, Juha Samela2, Michael Aziz3, Michael Brenner3 and Kai Nordlund2; 1Mathematics, Southern Methodist University, Dallas, Texas; 2Physics, University of Helsinki, Helsinki, Finland; 3School of Engineering and Applied Sciences, Harvard University, Boston, Massachusetts.

Despite more than 40 years of research since the first observation of patterns on ion-irradiated surfaces, a predictive model for the formation and selection of these patterns has remained elusive -- physically-derived models based on the assumptions of Bradley-Harper theory have been unable to explain many observed phenomena, whereas phenomenological models have relied on the use of fitting parameters to obtain experimental agreement. However, recent progress in both the /prompt/ crater-function regime and the /gradual/ energy-relaxation regime offer the promise of a quantitative, physically-derived model that agrees with recent experiments on Si, without the use of fitting parameters. Here, we report on the development of a parameter-free model with two novel components. For the prompt regime, angle-dependent crater-function measurements obtained using MD are upscaled directly into continuum PDE terms, revealing that the prompt regime is dominated by redistribution (not erosion!). For the gradual relaxation dynamics, a Maxwell visco-elastic model is used which allows stress build-up in the amorphous Si surface layer, and the relaxation of that stress via viscous flow. Together, these components offer improved agreement with with many of the experimental observations that have confounded theories to date.


10:45 AM II8.5
Self-organized Ripple Formation on Nickel: Influence of the Initial Surface Morphology on the Ripple Pattern by Ion Beam Sputtering. Tomas Skeren1,2, Kristiaan Temst1, Andre Vantomme1 and Wilfried Vandervorst2,1; 1Instituut voor kern- en stralingsfysica, Katholieke Universiteit Leuven, Leuven, Belgium; 2MCA, IMEC, Leuven, Belgium.

Surface roughening is often an unavoidable side effect of ion beam sputtering. However, it has been shown in the past, that application of the proper sputtering conditions can lead to the formation of 1D and 2D periodic nanopatterns with a high degree of self-organization and with periodicities ranging from few nanometers to several micrometers. We have performed a scanning tunneling microscopy study of the Ni surface evolution upon ion beam bombardment with 2 keV Ar+ ion beam. During the bombardment at angles higher than 60° we observed formation of the ripples parallel to the ion beam. The ripples start appearing from a fluence of ~5.10^15 ions/nm^2 and with a wavelength of about 8 nm. With increasing fluence the ripple wavelength grew linearly in our experiments up to fluences of 5.10^17 ions/nm^2 where it reached 65 nm. The high fluence needed to reach the large periodicities complicates the possible application of this technique. We examined a possibility to accelerate the formation and growth of the ripples by modifying the initial surface morphology of the Ni layer. Deposition of a thin capping layer (few nanometers) of different metals, such as Au or Pt, creates a layer composed of small islands with characteristic sizes which depend on the capping material, thickness and temperature. When this surface is sputtered we observe the formation of the ripples with sizes inherited from the island size of the capping layer. These ripples persist even after removing all the capping material and continue to grow upon further sputtering. By modification of the grain size of the capping layer, we have induced different wavelengths for the ripples in the underlying nickel layer and, remarkably, we have been able to create the ripples with a fluence that barely created any morphology changes on the plain Ni surface. In this way we have been able to accelerate the formation and the growth of the ripples on the Ni surface and to control their characteristic dimensions. The process breaks down when the initial islands become too large (more than ~100 nm) as the ripples then do not follow their size and grow independently with the original wavelength normally seen on Ni.. We have attempted to explain the observed behavior by using our computer model that involves surface diffusion, surface noise and sputtering non-linearity created by angular dependence of the sputtering yield.


11:00 AM II8.6
Mass Redistribution Causes the Structural Richness of Ion-irradiated Surfaces. Charbel Madi1, Eitan Anzenberg2, Karl F. Ludwig2 and Michael J. Aziz1; 1Harvard University, Cambridge, Massachusetts; 2Physics, Boston University, Boston, Massachusetts.

We show that the "sputter patterning" topographical instability is determined by the effects of ion impact-induced prompt atomic redistribution and that sputter erosion—the consensus predominant cause—is essentially irrelevant. We use Grazing Incidence Small Angle X-Ray Scattering to measure in situ the damping of noise or its amplification into patterns via the linear dispersion relation. A model based on the effects of impact-induced redistribution of those atoms that are not sputtered away explains both the observed ultrasmoothening at low angles from normal ion incidence and the instability at higher angles.


11:15 AM II8.7
3D-Chemical Imaging of Ion Beam Synthesized Au-Nanoparticles in Oxide Single-crystals. Suntharampillai Thevuthasan1, Satyanarayana V. Kuchibhatla1, Praneet Adusumilli2, Ty Prosa3, Vaithiyalingam Shutthanandan1, Robert Ulfig3, Bruce Arey1 and Chongmin Wang1; 1EMSL, Pacific Northwest National Laboratory, Richland, Washington; 2Northwestern University, Evanston, Illinois; 3Cameca Instruments Inc., Madison, Wisconsin.

Ion beam implantation of heavy ions such as Au+ in oxides and post-implantation annealing treatments has been shown to result in in situ nanoparticle formation. It was shown by earlier researchers that the embedded structures are of pure-Au, based on the electron microscopy and optical absorption analyses. However, the recent atom probe tomography (APT) analysis of the Au-implanted MgO samples question these results and the first set of conclusions indicate that the nanoclusters formed within the MgO matrix may consist of a mixture of Au, Mg and O as opposed to 100% Au as reported. Atom probe tomography, APT, is primarily a combination of point-projection microscopy and time-of-flight mass spectrometry. The three dimensional atomic structure of the sample tips can be obtained through a reconstruction of the experimental data generated by a progressive layer-by-layer evaporation of the atoms from the needle-shaped tip and accounting for the time-of-flight of the ions. Recently, the development of laser-assisted evaporation of materials has unveiled the great potential of atom probe tomography (APT) to analyze the insulating materials. APT is shown to provide chemical identity of the samples with atomic-scale resolution with a field-of-view better than 100 nm3. Here, we present the results of the detailed APT analysis of Au-nanoparticle embedded MgO single crystal samples. The analysis indicates that the clusters may contain a maximum of up to 60 - 70% Au only and the interface between the nanoparticle and the MgO matrix is often rich with Mg and O. We also observe that there is no significant presence of Au in the MgO matrix. The merits of the results will be discussed with respect to the influence of laser energy, cluster size and will be put in perspective by comparing the results with electron microscopy.


11:30 AM II8.8
The Origins of Ripple Formation on Ion Irradiated Semiconductor Surfaces. Jia-Hung Wu and Rachel S. Goldman; Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan.

Ion irradiation of semiconductor surfaces has emerged as a promising approach to generate a variety of self-organized nanostructures, including nanodots and ripples. Nanodots or pits have been reported to appear at normal beam incidence (θb = 0°) irradiation and evolve to flat surfaces and finally to ripples for θb in the range from 20° to 80°. In addition, the ripple wave vector is either parallel or perpendicular to the projected ion beam direction, often termed “parallel-mode” or “perpendicular-mode” ripples, respectively. In all experimental reports to date, ripples have been reported solely for θb ≠ 0°. The ripple formation mechanism has been explained in terms of a surface instability induced by the competition between a θb-dependent sputtering yield and surface diffusion (BH model).1 However, for several ion-irradiated surfaces, mass pile-up at the edges of craters (e.g. the formation of rims) has been reported. Although crater rims are not predicted by BH model, they have been explained by an additional contribution from atomic displacements (mass redistribution) during the irradiation process. Recently, a modified BH model, including mass redistribution, has been used to predict flat surfaces at low θb, and in some cases, ripple rotation from a perpendicular to a parallel mode with increasing θb.2 Clearly, the relative roles of sputtering and mass redistribution on ripple formation need to be clarified. Here, we report the formation of ripples on InSb surfaces using normal incidence of focused ion beams, and separately examine the influence of mass redistribution and sputtering by controlling the local curvature gradient with a variation in the distance between beam spots (pitch). Meanwhile, we examine the influence of mass redistribution on surface morphology by controlling the spatial distribution of displaced atoms with a variation in the pitch. With decreasing pitch, the surface morphology evolves from pits to perpendicular-mode ripples. These results suggest that ripple formation is dominated by ion-induced mass redistribution rather than sputtering. Further irradiation of rippled surfaces leads to the nucleation of nanodots at the ripple crests, followed by the growth of nanorod arrays, presumably due to nanodot-induced self-shielding. Detailed ripple and nanorod formation mechanisms based upon mass redistribution AND ion-induced lateral mass reditribution will be discussed3. This work is supported in part by AFOSR-MURI and ARO-DURIP Reference: 1R. M. Bradley and J. M. E. Harper, J. Vac. Sci. Technol. A 6, 2390 (1988). 2B. Davidovitch, M. J. Aziz, and M. P. Brenner, Phys. Rev. B 76, 12 (2007). 3R. M. Bradley and P. D. Shipman, Phys. Rev. Lett. 105, 145501 (2010).


11:45 AM II8.9
Nanostructures Formed on Polymeric Materials by Ion Beam with Glancing Angle Irradiation. Myoung-Woon Moon1, Tae-Jun Ko1,2, Kyu Hwan Oh2, Ashkan Vaziri3 and Kwang-Ryeol Lee1; 1Korea Inst. Sci. Tech., Seoul, Korea, Republic of; 2Seoul Natl Univ, Seoul, Korea, Republic of; 3Northeastern Univ., Boston, Massachusetts.

Surface engineering of polymeric materials has a broad array of scientific and technological applications that range from tissue engineering, regenerative medicine, microfluidics and novel lab on chip devices to building mechanical memories, stretchable electronics, and devising tunable surface adhesion for robotics. Recent advancements in the field of nanotechnology have provided robust techniques for controlled surface modification of polymers and creation of structural features of wrinkle, ripple or hairy on the polymeric surface at nanometer scale [1-2]. We have demonstrated robust techniques for controlled surface engineering of soft and relatively hard polymers using ion beam irradiation and plasma treatment, which allows the controlled fabrication of nanoscale surface features such as wrinkles, ripples, holes, and hairs in nano-scale with respect to the nature of each polymer. In this talk, we discuss further the formation of these structural features created with various ion incident angles from 0 upto almost 90 deg. This includes the change in the chemical composition of the surface layer of the polymers due to ion beam irradiation or plasma treatment and the instability and mechanics of the skin-substrate system. It was found that as increased the irradiation angle onto the substrate, the pattern showed anisotropic in geometries and growth patterns on soft polymer of polydimethylsiloxane or PDMS. References [1]. M.-W. Moon, et al , PNAS, 104 (2007) 1130-1133. [2]. M.-W. Moon, et al, Soft Matter 6 (2010), 6, 3924 - 3929.


 

SESSION II9: Novel Processing Techniques & Analysis I
Chair: Arkady Krasheninnikov

Thursday Afternoon, April 28, 2011
Room 3016 (Moscone West)


1:30 PM *II9.1
Ion Irradiation Effects in Silicon Nanowires. Kai Nordlund, Eero Holmström and Sanni Hoilijoki; Department of Physics, University of Helsinki, Helsinki, Finland.

Ion implantation is a standard method for introducing dopants into semiconductor s. While conventional implantation of course deals with irradiation of bulk mate rials, recent development of transistors using Si nanowires as the active compon ent raise the question of how ion implantation affects this low-dimensional syst em. Since a nanowire has a huge surface-area-to-volume ratio, one could expect o n one hand that sputtering and transmission is much more pronounced than in bulk Si, on the other hand that the surface might destabilize the system. Radiation effects in nanowires have been studies to some extent experimentally ( for a review see [1]), and major differences (such as a much larger radiation ha rdness in some nanowires materials) to bulk materials have been reported. In the particular case of Si nanowires, it appears that as in its bulk counterpart, al so the Si nanowire can be strongly damaged by the irradiation, and annealing ís necessary to obtain functional devices. However, the understanding of damage in Si nanowires is very poor. As a first step to obtain such understanding, we have carried out molecular dynamics computer simulations of ion irradiation of Si na nowires. We examined the threshold displacement energy and threshold sputtering energy in hexagonal Si nanowires with a <111>-oriented axis and with all side facets being <112> [2] . We found that the six non-equivalent surface positions have a sputtering threshold of approximately 10 to 15 eV, whereas the threshold displacement energy in the bulk core of the wire is the same as in regular bulk Si, 30 eV averaged over all lattice directions, for the Stillinger-Weber potential. We have also simulated 0.1 - 10 keV cascades in Si nanowires and compared the results to those in bulk Si and at Si surfaces. The results show that the damage production in the nanowire is strongly influenced by surface effects. [1] A. V. Krasheninnikov and K. Nordlund, J. Appl. Phys. (Applied Physics Review s) 107, 071301 (2010). [2] E. Holmström, A. Kuronen, and K. Nordlund, Phys. Rev. B 78, 045202 (2008)


2:00 PM II9.2
Post-CMOS Integration of Nanomechanical Devices by Direct Ion Beam Irradiation of Silicon. Francesc Perez-Murano1, Gemma Rius1,2, Jordi Llobet1 and Xavier Borrise1; 1Nanofabrication group, Instituto de Microelectronica de Barcelona (IMB-CNM, CSIC), Bellaterra, Spain; 2Surface Science Laboratory, Toyota Technological Institute, Nagoya, Japan.

We present the development of Focused Ion Beam (FIB)-based fabrication of nanomechanical devices monolithically integrated into CMOS circuits. With only two step process, the patterning and transfer of features to the structural layer is accomplished: direct exposure of silicon and poly-silicon surfaces by Ga+ FIB and transferee to the structural layer by standard microfabrication silicon etching processes. The ion beam modified silicon, acting as the etching mask, presents an outstanding robustness for both chemical and reactive ion etching process, enabling a simplified fabrication of nanomechanical devices with sub-micron resolution. As an example, double clamped silicon beams have been successfully defined and preliminary tested to determine the specific elastic properties of ion beam-modified Si structure. The compatiblity check to guarantee the integrity of the electronic performance of CMOS circuits after the energetic beam irradiation is also investigated and presented. Patterning based on direct ion beam exposure of silicon and etching presents advantages in comparison with electron beam lithography since it is realized without the use of any resist media, which is especially challenging for the non-flat CMOS pre-fabricated substrates. It is demonstrated that, if properly executed, ion beam patterning does not cause damage to the electronic performance of the adjacent CMOS circuits. References: 1) G. Rius, J. Llobet, J. Arcamone, X. Borrise, F. Perez-Murano. Microelectronic Engineering 86, 1046-1049 (2009). 2) G. Rius, J. Llobet, X. Borrisé, N. Mestres, A. Retolaza, S. Merino , F. Perez-Murano. J. Vac. Sci.Technol. B 27, 2691 (2009)


2:15 PM II9.3
Detection of Single Ion Arrival for Fabrication of Single Electron Spin Silicon Devices. Edward Bielejec, Nathan Bishop and Malcolm Carroll; Sandia National Laboratories, Albuquerque, New Mexico.

Single charge and spin devices are of interest for alternative computing approaches such as quantum computing. We present a fabrication pathway towards building single electron spin devices using single ion implantation. This talk will discuss results that demonstrate the key steps of this path and progress towards integrating these steps to demonstrate a single spin device. Four key steps to achieve this goal are: single ion detection capability using avalanche photodiodes (APD) detectors; demonstration of a nanostructure that can be used to interrogate and control the single electron device once the ion is implanted in to the nanostructure; integration of the nanostructure with the APD detector; and development of a focused nano-beam for spatially controlled implantation. Detection of the arrival of a single donor atom during the implantation step is achieved using an integrated avalanche photodiode APD technique (J. A. Seamons, et al. Appl. Phys. Lett. 93, 043124 2008). Laterally remote single ion detection was achieved by operating an APD in Geiger mode (E. Bielejec et al., Nanotechnology 21, 085201, 2010), which raised the possibility that this detector could be integrated with nanostructures placed near the detector. This greatly increases the flexibility of device fabrication allowing for future integration of single donor devices with additional nanostructures such as double quantum dots. Experimental results from a split-gate Si MOS device structure with timed donor implants (i.e., few donor device) demonstrates some of the principles of operation that would be used to interrogate a single spin. We will also present new results comparing APD Geiger mode detector efficiency as a function of substrate doping, device geometry and doping profiles designed to allow integration with a nanostructure device, a double quantum dot structure (E. P. Nordberg et al., Appl. Phys. Lett. 92, 202102 2009). Tight integration of these single spin devices will furthermore require a focused ion beam technology. We have developed a new nano-beamline (NBL) at SNL using an existing 400 keV HVEE implanter. To date the new beamline has demonstrated a sub-micron beam spot for a variety of ion species including H+ and Sb+. We have recently installed a series of beamline improvements to further reduce the spot size. The results from these upgrades will be presented. In summary, we present all key elements to fabricating single spin devices in silicon and discuss progress on the integration of these elements. This work was supported in full by the National Security Agency Laboratory for Physical Sciences under contract number EAO-09-0000049393. Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin company, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.


2:30 PM II9.4
Fabrication and Shape Control of Atomically Clean GaN Surfaces by Low-energy Ar+ Milling. Douglas M. Detert1,2, Petra Specht1, Oscar D. Dubon1,2, Damien Alloyeau3 and Christian Kisielowski3; 1Materials Science and Engineering, University of California, Berkeley, Berkeley, California; 2Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California; 3National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, Berkeley, California.

Ion-beam techniques have long been employed to fabricate thin, planar specimens for high-resolution transmission electron microscopy (HRTEM), but nm-scale implantation damage and amorphous layers produced by focused ion beam (FIB) processing limit the extent to which the bare surfaces of these samples can be studied. Here we present a method for creating atomically clean, periodic step edges on the surfaces of GaN nanostructures using high-energy (30 keV) FIB and low-energy (<1 keV) Ar+ milling. With this combination of processes we have fabricated 120 nm-wide GaN nanopillars with sharpened, atomically clean tips that have periodic, unit-cell-height step edges. Our fabrication process starts by using the FIB to create a cross-sectional lamella from an epitaxial GaN film grown on (0001) sapphire. Using conventional lift-out techniques, the lamella is then cut out and welded to the top of a post on a Cu transmission electron microscopy grid. The pillar is then milled parallel to its axis, producing a tapered needle with a circular cross section that is roughly 2 µm long and 150 nm wide at its base. The grid is transferred ex situ to a low-energy Ar+ ion mill (Fischione NanoMill model 1040) for thinning at 900 eV and cleaning at 500 eV. Selective targeting of the needle minimizes sputtering from the Cu support grid, thereby reducing re-deposition from the surrounding area. HRTEM imaging reveals that step edges on the tip exhibit a periodicity that is dependent on the tip surface angle relative to the GaN(0001) vicinal plane. Because the step edge density on the needle surface is a function of the tip angle, it can be controlled by both the angle and the energy of the Ar+ beam. In principle, this technique can be extended to other materials systems, creating an attractive platform for the investigation of the behavior of catalytic nanoparticles on stepped surfaces. This work was funded by the Helios Solar Energy Research Center, and FIB and HRTEM work was performed at the National Center for Electron Microscopy. Both facilities are supported by the Director, Office of Science, Office of Basic Energy Sciences of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.


2:45 PM II9.5
Structural Changes Induced by Swift Heavy Ion Beams in Tensile Strained Al (1-x)InxN /GaN Hhetero Structures. G. Devaraju, Anand p. Pathak, N. Srinivasa Rao, V. Saikiran and N. Sathish; School of Physics, University of Hyderabad, Hyderabad, A P, India.

III-Nitride compound semiconductors have tremendous applications in opto electronic, high frequency and high power devices. In spite of huge defect densities (four orders of magnitude), compared to their counterpart GaAs, they are extensively used in devices. The strain generated by lattice and thermal mismatch offers an extra degree of freedom to tune the optoelectronic properties. Swift heavy ion (SHI) irradiation is a post growth technique to alter structural and optical properties. Under this energy regime, ions loose energy by depositing to target electrons. Hence, the structural changes in Al(1-x)InxN would occur due to the intense ultra fast excitations of electrons along the path of the ions. In the present case Al (1-x) InxN with x=0.12 composition has been grown on a c-plane sapphire substrate with insertion of GaN as a layer between them, which are realized with metal organic chemical vapour deposition (MOCVD) technique. Ion species and energies are chosen such that electronic energy deposition rates differ significantly in Al(1-x)InxN and are essential for understanding the ion beam interactions at the interfaces. Thus the samples are irradiated with 80 MeV Ni6+ and 100 MeV Ag8+ ions at varied fluences (1e12 and 1e13 ions/cm2) to alter the structural properties. We employed different characterization techniques like High Resolution X- ray Diffraction (HRXRD), Rutherford back scattering spectrometry (RBS) and Raman spectroscopy to estimate composition, thickness, strain and to know vibrational phonon modes. HRXRD and RBS experimental spectra have been fitted with Philip’s epitaxy, SIMNRA code, which yields thickness and composition from compound semiconductors. The surface morphology of pristine and irradiated samples is studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM).


3:30 PM *II9.6
Ion Beams for Synthesis and Modifications of Nanostructures in Semiconductors. Anand p. Pathak, N. Srinivasa Rao, G. Devaraju, V. Saikiran and SVS Nageswara Rao; School of Physics, University of Hyderabad, Hyderabad, A P, India.

It is proposed to present a review of our recent work on synthesis and modifications of nanocrystals/ quantum dots of Ge, Si embedded in silica matrix on Si substrate and other III-V compounds on other substrates like sapphire or other suitable substrates. The initial synthesis is done by using atom beam co-sputtering, RF magnetron sputtering or ion implantation followed by RTA, Swift heavy ion irradiation or microwave annealing. Relative merits of these annealing and irradiation techniques will be highlighted. The nanocrystals thus synthesized are studied using Rutherford backscattering spectrometry (RBS) to measure the composition and film thickness. The structural characterization is performed by using X-ray diffraction (XRD) and Raman spectrometry. Surface morphology of the samples has been studied by atomic force microscopy (AFM). The effects of various parameters like irradiation fluence and annealing temperature etc on the nanocrystal formation and their size and distribution are being investigated. The up to date results will be presented during the meeting in April 2011. *Corresponding author E-mail: appsp@uohyd.ernet.in Tel: +91-40-23010181/23134316, Fax: +91-40-23010181 / 23010227.


4:00 PM *II9.7
Ion Beam Modification of Nanocrystalline Cubic Ceria and Zirconia. Yanwen Zhang1,2, Philip D. Edmondson1, Sandra Moll3, Fereydoon Namavar4, Tamas Varga3, Mark E. Bowden3, Weilin Jiang3 and William J. Weber2,1; 1Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee; 2Department of Materials Science & Engineering, University of Tennessee, Knoxville, Tennessee; 3Pacific Northwest National Laboratory, Richland, Washington; 4University of Nebraska Medical Center, Omaha, Nebraska.

Nanostructured materials provide the opportunity for tailoring physical, electronic, and optical properties for a variety of technological applications, including advanced nuclear energy systems. As the world increases its reliance on nuclear energy, there is an ever-increasing demand for radiation-tolerate materials that can withstand the extreme radiation environments in nuclear reactors, accelerator-based nuclear systems, and nuclear waste forms. Understanding radiation effects in nanomaterials is an urgent challenge, since it may hold the key to unlock the design of tailored materials for advanced nuclear energy systems. Cubic ceria and zirconia are well known ionic conductors that are also isostructural with urania, plutonia, and thoria-based nuclear fuels. Understanding role of nanograined structures under ion beam modification has significant implication in advanced nuclear energy systems. Grain growth, oxygen stoichiometry and phase stability of nanostructurally-stabilized cubic zirconia and ceria are investigated under energetic Au ion bombardment at 160, 300 and 400 K to doses up to 35 displacements per atom. The initial grains size of ~8 nm increases with irradiation dose to a saturation value that is temperature dependent. Slower grain growth is observed in zirconia under irradiation at 400 K irradiations, as compared to 160 K irradiation, indicating that thermal grain growth is not activated and irradiation-induced grain growth is the dominating mechanism. Faster grain growth in ceria is observed with increasing temperature, indicating thermally-enhanced dynamics. While the cubic structure is retained to high irradiation doses at all temperatures for both zirconia and ceria, oxygen reduction in the irradiated films is detected. The loss of oxygen suggests a significant increase of oxygen vacancies in nanocrystalline zirconia and ceria under ion irradiation. The oxygen deficiency may be essential in stabilizing the cubic phase to larger grain sizes.


4:30 PM II9.8
Broad Ion Beam Treatment for Geometry and Surface Energy Controllable Bio-inspired Dry Adhesives. Yudi Rahmawan2,1, Myoung-Woon Moon2, Tae-Il Kim1, Kwang-Ryeol Lee2 and Kahp-Yang Suh1; 1Mechanical Engineering, Seoul National University, Seoul, Korea, Republic of; 2Korea Institute of Science and Technology, Seoul, Korea, Republic of.

Many functional surfaces in nature are made of long fibrillar structures in the hierarchy of micro- and nanometer scale. Typically in the gecko foot, the fibrillar structures are made from low elastic modulus and hydrophobic β-keratin material (wetting angle ~120° and E= 1-3GPa). This material has been responsible for the unique properties of the gecko foot such as high dry adhesion strength, self cleaning effect, durability and easy detachment. In this work, we study in detail the effect of intimate contact area and intrinsic surface energy contributions to the adhesion strength of artificial nanoscale fibrillar structures. The artificial nanoscale fibrillar structures (pillars array of 100nm dia. and 1μm height) were fabricated using soft polymeric material (wetting angle ~86° and E=20-300MPa) by conventional photolithographic and soft lithographic processes. The tilting angle of nanoscale fibrillar structures was controllable by the incident ion beam direction of Ar ion beam bombardment in a linear broad ion gun system. The intrinsic surface energy was varied with elapsing time after oxygen ion treatment of the same device. The resulted surface assembly was characterized using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and standard surface energy measurement. The shear adhesion strength was measured by hanging scales method on both hydrophobic and hydrophilic substrates. Our first finding shows that sloping ion beam bombardment can be efficiently used to make tilted nanoscale fibrillar structures up to 76° from the surface normal uniformly in a large area. The exposed surface produced a thin stiff skin and bends the pillars to the ion beam direction. The increasing contact area due to the nanoscale fibrillar structures bending would increase the preferred Van der Waals force between the two surfaces. Next, the oxygen ion beam treatment increased the surface energy of polymeric material from 21.26±0.99 mN/m to 72.84±0.32 mN/m. A direct consequence of increasing shear adhesion force of about three times was observed showing that capillary force also significantly contributed to the adhesion strength in the system. This result is in line with XPS measurement where the peak for hydroxyl group and oxygen content increased significantly in the sample after oxygen treatment. The high surface polarity of the hydroxyl group after oxygen treatment on the sample would easily attract water film that may present in every surface and induced the capillary force. Finally, we confirm that the optimum combination of intimate contacting area of nanoscale fibrillar structure and high intrinsic surface energy could produce a dry adhesive with the total shear adhesion force of 12.66±1.58 kgf/cm2 which is more than 10 times stronger than real gecko foot (~1kgf/cm2). This result enables the design of ultra high adhesion strength dry adhesives which would be potentially useful for microelectronic or biomedical devices.


4:45 PM II9.9
Enhanced Adhesion of Coating Layers by Ion Beam Mixing: Applications for Nuclear Hydrogen Production and Metal Printed Circuit Board. Jae-Won Park, Hyung-Jin Kim, Sunmog Yeo and Seong-Duk Hong; Korea Atomic Energy Research Institute, Daejon-City, Korea, Republic of.

The ion beam improves the ceramics/metal bonding by mixing atoms at interface. The ion beam mixing (IBM) can be used as a tool in fastening a thin seed coating layer to a substrate. The thin layer coating/IBM process can be repeated for the thicker mixed seed layer. Subsequently, additional coating layer can be deposited onto the mixed seed layer to the designed thickness. Two applications that the IBM plays crucial roles are presented. One is the SiC coating on Hastelloy X for an application at very high temperatures (> 900 degree C) and under extremely corrosive environmental conditions such as the hydrogen production thermo-chemical plant operated using the heat generated from the very high temperature reactor (VHTR). The other is Cu conductive coating on aluminum oxide layer formed by anodizing method on an aluminum alloy substrate for a long term safe operation of a higher flux light emitting LED. Our study finds the followings: In general, ion beam improves the ceramic/metal bonding by mixing atoms at interface and forming new phases at the expense of coating and substrate materials during a thermal process, but the thermodynamics of intermixed junction materials plays an important role for the stability of the bonded interface at the elevated temperature. A careful materials selection is thus needed. Another critical issue to be carefully considered is the depth of ion penetration determined by the ion energy and the required thickness of the coating layer. One of the merits of IBM is that the surface pretreatment is not imperative for the metallic substrate as in conventional diffusion bonding, because a forceful intermixing by the energetic ions mitigates the effect of the initial surface conditions.


 

SESSION II10: Novel Processing Techniques & Analysis II
Chair: Karl-Heinz Heinig

Friday Morning, April 29, 2011
Room 3016 (Moscone West)


8:30 AM II10.1
MS&E Research and Training using Ion Beams. Daryush Ila, Robert L. Zimmerman, Claudiu I. Muntele, Lawrence R. Holland and S. Budak; Physics, Alabama A&M University, Huntsville, Alabama.

The Accelerator facility at the Center for Irradiation (CIM) of Materials @ AAMU (http://cim.aamu.edu) established in 1990 to serve the University in its research, education and services the need of the local community and Industry. CIM irradiation capabilities oriented around two tandem type ion accelerators with seven beam lines providing high resolution Rutherford backscattering spectrometry (RBS), MeV focus ion beam, high energy ion implantation and irradiation damage studies, particle induced x-ray emission (PIXE), particle induced gamma emission (PIGE), and ion induced nuclear reaction analysis in addition to fully automated ion channeling. One of the two tandem ion accelerators designed to produce high flux ion beam for high fluence MeV ion implantation and high fluence ion irradiation damage study. The CIM facility is well equipped with variety of surface analysis systems, such as SEM, ESCA, as well as scanning micro-Raman analysis, UV-VIS Spectrometry, luminescence spectroscopy, nanoscale thermal conductivity, electrical conductivity, IV/CV systems, mechanical test systems, AFM, FTIR, Voltmetry analysis as well as low energy implanters, Ion Beam Assisted Deposition and MBE systems. In this presentation we will demonstrate how the facility provides education and training services to schools, industries and how highlight few of the recent inventions at CIM. Sponsors: Supported in part by NSF, NASA, DOE and industries.


8:45 AM II10.2
A Novel Strategy to Maximize Deposition Efficiency and Electrical Conductivity for Electron Beam Induced Pt Deposition as a Gentle Alternative to Ion Beam Assisted Deposition. Harald Plank1,2, Stephan G. Michelitsch2, Christian Gspan1,2, Andreas Hohenau3, Joachim Krenn3, Gerald Kothleitner1,2 and Ferdinand Hofer1,2; 1Institute for Electron Microscopy, Graz University of Technology, Graz, Austria; 2Graz Centre for Electron Microscopy, Graz, Austria; 3Institute for Physics, University of Graz, Graz, Austria.

During the last decade particle induced deposition of conducting (Pt, W, Au, …) or insulating (SiOx, …) materials from a gaseous precursor via ions or electrons has become an essential part of focused ion beam (FIB) based processes such as ion lithography, device fabrication and modification, or multi-purpose surface patterning down to the nanometer range. However, the use of ions on critical samples such as nanoscale devices or soft matter specimens can cause significant problems due to sputter contributions, unwanted ion implantation or considerable thermal stress. Hence, electron beam induced deposition (EBID) attracts more and more attention as complementary tool to FIB related processes due to its wide absence of the mentioned drawbacks. However, EBID shows two major problems which have to be solved: i) low deposition rates, making this technique time and cost intensive; and ii) chemical impurities (mostly carbon) which influence the intended functionality such as electrical conductivity, which is of particular interest for electronic, optoelectronic, or sensor applications. During the last years different procedures have been applied before, during and after electron induced deposition to address both problems whereby clear emphasis was put on purification strategies. E.g. the highest conductivity for electron assisted Pt deposits has been achieved by thermal post-annealing at 300°C in an 1 ppm O2 atmosphere reducing the resistivity from 107 µΩ.cm to 104 µΩ.cm, however, resulting in a strongly porous structure due to the massive loss of carbon. Although such treatments are applicable to some samples many substrate materials (soft matter, biological, …) would strongly suffer from high temperature treatments in combination with reactive atmospheres. Hence, other ways have to be found to enhance the functionality for e.g. conducting materials deposited via EBID. In this work we demonstrate how deposition rates and conductivities for Pt deposits can be maximized by a simple strategy applicable for all electron microscopy suited samples without external curing procedures. As a first step the deposition efficiency is increased about a factor of > 3 by simple but efficient changes of beam parameters during deposition. In a second step, the electron beam is used to decrease the resistivity more than two orders of magnitude (< 105 µΩ.cm) with a rate better than 1 min/µm3. Beside the practical aspect of the work, a detailed investigation reveals the establishment of a specific working regime during deposition as the key element for the improvements. This leads to a high number of partially dissociated precursor molecules which are trapped within the deposit. The specially tailored post-treatment is then able to finish the dissociation process leading to strongly improved conductivities without any high temperature ex-situ steps. This allows for manifold combinations with FIB processes due to the gentle nature of highly efficient EBID processes.


9:00 AM II10.3
Molecular Dynamic-secondary Ion Mass Spectrometry (D-SIMS) Excited by C60+-Ar+ Co-ionization. Jing-Jong Shyue1,2, Yun-Wen You1, Hsun-Yun Chang1, Wei-Chun Lin1 and Chi-Jen Chang2; 1Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan; 2Department of Materials Sciences and Engineering, National Taiwan University, Taipei, Taiwan.

Cluster ion sputtering has been proven to be an effective technique for depth profiling of organic materials. In particular, C60+ ion beams are used to profile soft maters. The limitation of carbon deposition associated with C60+ sputtering can be alleviated by concurrently using a low-energy Ar+ beam. In this work, the role of this auxiliary atomic ion beam was examined by using an apparatus that could analyze the sputtered materials and the remaining target simultaneously using dynamic secondary ion mass spectrometry (D-SIMS) and x-ray photoelectron spectrometry (XPS), respectively. It was found that the auxiliary 0.2 kV Ar+ stream was capable of slowly removing the carbon deposition and suppresses the carbon from implantation. D-SIMS of poly(ethylene terephthalate) (PET) and Poly(methyl methacrylate) (PMMA) was also excited by various combinations of continuous C60+ and Ar+ ion sputtering. Individually, the Ar+ beam failed to generate fragments above 200 m/z, and the C60+ beam excited molecular fragments of >1000 m/z. By combining the two beams, the auxiliary Ar+ beam extends the sputtering range of the C60+ beam and allows for the use of this technique in molecular D-SIMS. Another advantage to this technique is that the high ion yield and sputtering rate of C60+ generates adequate high-mass fragments that mask the damage from the Ar+ beam. As a result, fragments with ~900 m/z can be clearly observed. In addition, a more steady sputtering condition was achieved more quickly with co-sputtering than by using C60+ alone. Furthermore, co-sputtering yields a smoother surface than single C60+ sputtering, leading to possible better depth resolution than single C60+ sputtering.


II10.4 

Abstract Withdrawn 


 

SESSION II11: Networking & Discussion - Coming Events, Trends, Challenges
Chair: John Baglin

Friday Morning, April 29, 2011
Room 3016 (Moscone West)


10:00 AM II11.1
New Directions of the Ion Beam Modification of Materials. Daryush Ila, Physics, Alabama A&M University, Huntsville, Alabama.

Only relatively recently have high energy ion beams been used to modify and improve materials for applications in medicine and biology, even more recent has been the application of ion beam for nano-science and nanotechnology. Our team has been among a few other pioneer research groups in the ion beam community who have studied the interaction of ion beam for nanoscience and nanotechnology, specifically the interaction of MeV ions in its track through variety of materials with applications for control cell adhesion, improved surface properties of polymers used for heart-valve, for hip-joint implants, for fabrication of nanopores, for nanolithography, as well as to change the surface properties of bio-compatible polymers for controlled drug/medication delivery, nanostructure formation, and fabrication of sensors and thermoelectric materials. This presentation will include examples of new trends in ion beam modification of polymers and metals for percutaneous devices and other implants, for fabrication of nanopores, and surface modification of ceramics and semiconductors in order to fabricate sensors for extreme environment as well as for fabrication of highly efficient thermoelectric materials, taking advantage of the nano-structures produced in the ion beam track. Since there is a separate session on nanolithography, we will slightly touch the most recent development on ion beam application for nanolithography and projection ion beam.



10:15 AM NEWS & DISCUSSION:


Participants are invited to offer information, comments, News (including up to 3 slides), related to:

New Facilities and collaborations; Resources available; Future needs and opportunities. Student opinions and ideas welcome.

Moderator : John Baglin

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