Symposium Organizers
Vladimir Matias Los Alamos National Laboratory
Robert Hammond Stanford University
Guus Rijnders University of Twente
Darrell Schlom The Pennsylvania State University
U1: Ion Scattering
Session Chairs
Vladimir Matias
Frances Ross
Monday PM, November 27, 2006
Room 300 (Hynes)
10:00 AM - **U1.1
Studies of Multifunctional Thin Film Growth and Interface Processes via Integrated In Situ Time-of-Flight Ion Beam and X-Ray Photoelectron Spectroscopy
Orlando Auciello 1
1 Materials Science Division, Argonne National Laboratory, Argonne, Illinois, United States
Show AbstractWe have developed unique combinations of in situ and ex situ analytical techniques capable of providing information about thin film growth and interface processes at the atomic scale. The in situ techniques include time-of-flight ion scattering (TOF-ISARS) and mass spectroscopy of recoil ions (MSRI), functional in relatively high background pressure environments such as growth of oxide films in oxygen atmospheres. These techniques are not only powerful for understanding fundamental thin film science, but are also useful for establishing composition-microstructure-property relationships critical for the development of materials integration for fabrication of film-based micro and nanodevices. We will discuss examples of application to understanding ferroelectric and high-k dielectric film growth and interface processes and using this knowledge for developing integration of ferroelectric capacitors with silicon microcircuits for non-volatile ferroelectric random access memories (FERAMs), development of high-K dielectric capacitors for high-frequency devices, and development of new high-K dielectric layers for the next generation of nanoscale CMOS gates. This presentation will include a review of studies of a new TiAl layer developed in our laboratory that can be used as a material with a double diffusion barrier / bottom electrode functionality for integration of ferroelectric capacitors with CMOS devices for fabrication of FeRAMs, high-K dielectric layers with Cu electrodes for high frequency devices, and as a new high-K dielectric for the next generation of nanoscale CMOS devices. We will discuss results from systematic studies designed to understand TiAl film growth and oxidation processes using sputter-deposition in conjunction with complementary in situ characterization techniques mentioned above and ex situ transmission electron microscopy and electrical characterization. This work was supported by the US Department of Energy, BES-Materials Sciences, under Contract W-13-109-ENG-38.
10:30 AM - **U1.2
Mass Spectrometry of Recoiled Ions for In-situ Surface Analysis: Status and Possiblities.
J. Albert Schultz 1
1 , Ionwerks Inc., Houston, Texas, United States
Show AbstractMass Spectrometery of Recoiled Ions (MSRI) in combination with time of flight ion and neutral scattering spectrometery (INSS) have been used in a number of laboratories for monitoring and controlling surface elemental composition during thin film growth processing. Pulsed keV ion beams impinge a growing surface at grazing incidence and the recoiled elements and ions which are either scattered (INNS) or recoiled (MSRI) into a forward direction are measured by their time of flight between the surface and an ion detector positioned some tens of cm away. Surface compositions can be inferred by INSS from energy losses of the scattered neutrals or ions. MSRI enables qualitative mass spectrometry from the surface by time of flight reflectron mass spectrometry of the ionized directly recoiled elements.The limitations of these two techniques becomes apparent when trying to devise instrumentation which can provide even semi-quantitative surface analysis at time scales of a few seconds and precisions of a few ppm. The possibilities of alternative but related approaches to rapid surface analysis which may now be possible (given advances in laser and detection technology) will be suggested and discussed.
11:00 AM - U1: Ions
BREAK
12:00 PM - **U1.4
Time-of-Flight Ion Scattering Spectroscopy of Oxide Thin Films: Surface Structure Analysis and Sensitivity to Atomic Layer-by-layer Engineering.
Adrian Gozar 1 , Gennady Logvenov 1 , Ivan Bozovic 1
1 Condensed Matter and Materials Science, Brookhaven National Laboratory, Upton, New York, United States
Show AbstractWe report results of angle resolved time-of-flight ion scattering and Mass Spectroscopy of Recoil Ions (MSRI) data in charge density wave BaBiO3 and high temperature superconducting (HTS) cuprate thin films grown by Molecular Beam Epitaxy.The BaBiO3 spectra show that the film has a pure BiO termination layer. The time-of-flight data at 270 total scattering angle display dramatic changes when the azimuth angle is changed by as little as one degree. These data reveal an atomically smooth film surface and, in conjunction with computer simulations, should allow us to determine the crystal structure of the surface layers. We also show that the angle resolved MSRI spectra correlate with the quantitative results obtained from Direct Recoil Spectroscopy (DRS), enabling one to use it for accurate surface crystallography.Real time in-situ analysis of HTS thin film growth is performed for La_2-xSr_xCuO_4 and Bi_2Sr_2CaCu_2O_6+delta. The spectra show sensitivity to deposition of fractions of atomic monolayers. Results of the analysis of angular resolved time-of-flight DRS and MSRI spectra performed in order to quantitatively determine the surface composition and structure at every stage of the film growth are discussed.
12:30 PM - U1.5
Ion Scattering Studies of High-κ Gate Stacks: Thermal Stability and Interdiffusion
Lyudmila Goncharova 1 , Tian Feng 1 , Eric Garfunkel 2 , Torgny Gustafsson 1
1 Physics, Rutgers University, Piscataway, New Jersey, United States, 2 Chemistry, Rutgers University, Piscataway, New Jersey, United States
Show AbstractTo enable the selection of appropriate novel materials in nano-electronics, the ultrathin film and interface properties of adjoining materials must be understood at the atomic scale. A wide range of chemical stability and electronic structure issues need to be understood to allow the integration of high-κ dielectrics and metal electrodes in nanoscale CMOS. We will present results on the structure and composition of two different classes of potentially interesting high-κ materials, mainly obtained with medium energy ion scattering (MEIS), a high-resolution, low energy version of Rutherford Backscattering (RBS). We will discuss amorphous or polycrystalline films of materials such as HfO2, ZrO2, Y2O3, etc and present data on their thermal stability and reactivity to adjoining semiconducting channel and gate electrode materials. We will also discuss recent results on the use of isotopically labeled oxygen to learn about how oxygen reacts with and exchanges in the films, as oxygen chemistry appears critical to understanding defects in these systems. Additionally, results on the stability of ultrathin dielectrics on alternative channel materials (Ge and GaAs) will be presented.SRC, Sematech, NIST and NSF are gratefully acknowledged for their financial support.
U2: Electron Microscopy
Session Chairs
Adrian Gozar
Darrell Schlom
Monday PM, November 27, 2006
Room 300 (Hynes)
2:30 PM - **U2.1
In situ Electron Microscopy as a Tool for Imaging the Growth of Nanostructures.
Frances Ross 1 , Suneel Kodambaka 1 , James Hannon 1 , Ruud Tromp 1 , Mark Reuter 1 , Arthur Ellis 1 , Jerry Tersoff 1
1 , IBM T.J. Watson Research Center, Yorktown Heights, New York, United States
Show AbstractNew PresenterMonday 11/27*U2.11:30 - 2:00 PMIn situ Electron Microscopy as a Tool for Imaging the Growth of Nanostructures. Suneel Kodambaka
3:00 PM - **U2.2
A New Design for an Energy-Filtered, Aberration-Corrected LEEM/PEEM Instrument
Rudolf Tromp 1
1 , IBM T.J. Watson Research Center, Yorktown Heights, New York, United States
Show Abstract3:30 PM - U2: Electrons
BREAK
4:30 PM - **U2.3
Quantum Effects in Low Energy Electron Microscopy: a 3D view of Thin FilmGrowth and Structure.
Michael Altman 1
1 Department of Physics, Hong Kong University of Science and Technology, Kowloon Hong Kong
Show Abstract5:00 PM - U2.4
Real-Time Oxidation Studies of Ru(0001) Using Low-Energy Electron Microscopy and Nanospectroscopy.
Jan Flege 1 , Peter Sutter 1
1 Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York, United States
Show AbstractThe oxidation of metallic Ru(0001) leads to the epitaxial growth of RuO2(110), a catalytically highly active surface oxide. In oxidation catalysis under oxygen-rich conditions this oxide likely forms dynamically, and a detailed understanding of the oxidation reaction is important for efforts to optimize catalytic activity. Yet, despite extensive efforts, the reaction kinetics and the nanoscale growth mechanisms remain poorly understood.We have used low-energy electron microscopy (LEEM) to study Ru oxidation. Our experiments employ NO2 as the oxygen carrying precursor, and make full use of the powerful real-time imaging capability of LEEM at variable temperature. Depending on the substrate temperature during NO2 exposure, three different growth regimes are identified: At low temperatures, nanoscale oxide islands nucleate heterogeneously at step bunches and surface defects. At intermediate temperatures, the preference for step-edge nucleation is lifted, and anisotropic RuO2 islands grow on the entire metal surface, exhibiting the symmetry of the hexagonal Ru(0001) surface net. At high temperatures, finally, homogeneous nucleation and the growth of rounded 2D RuO2 islands is observed. By evaluating video-LEEM data recorded for different sample temperatures and oxygen partial pressures, anisotropic energy barriers, pressure-dependent growth rates, and oxygen capture zones could be quantified, providing a comprehensive understanding of the microscopic oxidation mechanism and its kinetics.Finally, photoemission electron microscopy and micro x-ray photoelectron spectroscopy have been applied using a newly-installed photoemission microscope at the National Synchrotron Light Source. These experiments provide a link between the evolution of the surface morphology and the chemical composition during the oxidation reaction.
5:15 PM - **U2.5
In Situ Scanning Electron Microscopy of Single-Walled Carbon Nanotube Growth during Chemical Vapor Deposition.
Yoshikazu Homma 1 2 , Daisuke Takagi 1 , Iwao Wako 1
1 Department of Physics, Tokyo University of Science, Shinjuku, Tokyo, Japan, 2 CREST, Japan Science and Technology Agency, Kawaguchi, Saitama, Japan
Show Abstract Understanding of the growth process of single-walled carbon nanotubes (SWCNTs) is crucial to achieve the growth control of them. In situ observation is a direct way to elucidate the growth process. We have developed an in-situ observation technique for chemical vapor deposition (CVD) of SWCNTs using a scanning electron microscope (SEM). We grew SWCNTs in the SEM using catalytic CVD with ethanol. Ethanol vapor of 10-20 Pa was introduced into the sample chamber with a flow rate of 50-80 sccm by pumping with a mechanical scroll pump. Growth temperature was 600-700°C. SWCNT growth and the SEM observation in high vacuum were done alternately while keeping the substrate at the growth temperature. To observe a growth process successively, ethanol exposure and observation without ethanol were repeated. In our observations, catalyst particles were on the substrate surface (i.e., root growth mode). In the initial stage of growth on the flat surface, most SWCNTs stood on the substrate surface, but they fell down on the surface after reaching the length of 100-200 nm. This is an indication that catalyst particles are not fixed on the substrate surface. As for the diameter of grown SWCNTs, ex situ Raman spectroscopy in combination with in situ SEM observation indicated that the diameter distribution of SWCNTs was narrow (1.0-1.3 nm) in the very beginning of the ethanol supply, and it became larger (0.4-2 nm) as growth proceeded. This may be related to the Ostwald ripening of catalyst particles. On the patterned substrate, suspended SWCNT formation and bundling process was revealed. During growth from a pillar top, the extension direction of a SWCNT fluctuated by 30-40°. This is another indication of catalyst particle movement on the substrate surface. Nearest-neighbor-bridge formation is enhanced as a result of fluctuation of extension direction during growth on a pillar array. Several bundle-bridge formation processes have been observed: bundling to already existing SWCNTs including growth along the initial one and touching of a newly grown SWCNT to the initial one by fluctuation of extension direction. Merging of two parallel bridges is also the mechanism of bundling. Bridging structures and bundle structures are not very rigid. They occasionally showed detaching or debundling behaviors. SEM imaging shows dynamic changes of nanotube architectures during growth.
5:45 PM - U2.6
Chemical Mapping of Individual Semiconductor Nanostructures.
Fulvio Ratto 1 , Andrea Locatelli 2 , Stefano Fontana 2 , Sharmin Kharrazi 3 , Shriwas Ashtaputre 3 , Sulabha Kulkarni 3 , Stefan Heun 4 , Federico Rosei 1
1 , INRS - EMT, Varennes , Quebec, Canada, 2 , Sincrotrone Trieste S.C.p.A., Basovizza, TS, Italy, 3 , University of Pune, Pune India, 4 , TASC – INFM, Basovizza, TS, Italy
Show Abstract
Symposium Organizers
Vladimir Matias Los Alamos National Laboratory
Robert Hammond Stanford University
Guus Rijnders University of Twente
Darrell Schlom The Pennsylvania State University
U3: RHEED
Session Chairs
Robert Hammond
Guus Rijnders
Tuesday AM, November 28, 2006
Room 300 (Hynes)
10:00 AM - **U3.1
Use of RHEED Combined with Other Spectroscopic Methods for in-situ Characterization of Material Deposition.
Philippe Staib 1
1 , Staib Instruments, Williamsburg, Virginia, United States
Show Abstract10:30 AM - **U3.2
High-pressure RHEED Controlled PLD of Complex Oxides.
Dave Blank 1 , Guus Rijnders 1
1 MESA Institute of Technology, University of Twente, AE Enschede Netherlands
Show AbstractRecent developments in strongly correlated materials, in particularly metal oxides, have led to many inventive ideas to apply these materials in novel device concepts. During the last decade a tremendous progress has been made in controlling these complicated materials. To name a few, these are the epitaxial growth technique, understanding of the properties of their defect structure, atomic-level control of their layering, in the case of oxides the manipulation of the oxygen contents and dopant densities, etc.. With our development of high-pressure reflection high-energy electron diffraction during pulsed laser deposition we are able to control the growth of these materials at atomic level. Two independent processes, i.e., nucleation and growth, play an important role during vapour-phase epitaxial growth on an atomically flat surface. Here, nucleation causes the formation of surface steps and subsequent growth causes the lateral movement of these steps. Both processes are determined by kinetics, since they take place far from thermodynamic equilibrium, and affect the final surface morphology. The applicability of high-pressure RHEED to extract the kinetic parameters, determining the growth of complex oxides in PLD, will be demonstrated. In PLD, deposition and growth are separated in time, which enables measurement of the kinetic parameters at growth conditions by monitoring the decay of the adatom density between the deposition pulses and the influence of the kinetics on the epitaxial growth of oxides will be presented.With this controlled growth one is able to design artificial materials with specific properties by atomic-scale tailoring of their compositions. In this presentation we will focus on the epitaxial growth of such heterostructures with special emphasis on growth kinetics as well as the termination control of each deposited layer (final and starting atomic configuration).
11:00 AM - U3: RHEED
BREAK
11:30 AM - **U3.3
Advances in the use of RHEED-TRAX and Cathodoluminescence for In-Situ Growth Characterization and Control.
Thomas Myers 1 , Kyoungnae Lee 1 , Randy Tompkins 1 , Eric Schires 1 , David Lederman 1
1 Physics, West VIrginia University, Morgantown, West Virginia, United States
Show AbstractReflection high-energy electron diffraction (RHEED) is one of the most robust and widespread techniques used for in-situ monitoring during molecular beam epitaxy (MBE) growth. Thus, all MBE systems have an electron gun allowing additional electron-beam stimulated in-situ characterizations. At WVU we are developing two such techniques, spectral analysis of cathodoluminescence (CL) in wide bandgap semiconductors and reflection high-energy electron diffraction-total reflection angle x-ray spectroscopy (RHEED-TRAXS) for in-situ composition monitoring and control.A pressing issue remaining for epitaxial growth is real-time compositional control to a high level of accuracy. For many materials, such as multi-element nitrides and oxides with unity sticking coefficients, it would be extremely beneficial to monitor the composition to a fraction of a monolayer. This technique needs to be both element-specific and surface-sensitive. RHEED-TRAXS is a leading contender as such a technique. The electron beam from a RHEED gun impinges on the sample at a small angle of incidence approximately equal to the critical angle for x-ray reflection. This geometry ensures that the measurement is extremely surface sensitive. This technique can be used to obtain both structural information, via RHEED, and chemical information, via x-ray detection. We are currently developing a compact RHEED-TRAXS using a state-of-the-art Si P-intrinsic-N (PIN) photodiode technology. We have used this system to investigate Ga and In coverage during the growth of GaN, and have observed Ga bi-layer evolution during growth, Mg destabilization of the Ga wetting layer, and significant In surface segregation. We are also investigating the in-situ, real-time composition measurements in complex oxide systems such as YMnO3 with promising initial results.In-situ cathodoluminescence (CL) occurring during RHEED is a strong candidate to determine the growth temperature and alloy composition for wide bandgap semiconductors. CL is easily detected up to and beyond typical growth temperatures for GaN and InGaN, accurately and reproducibly determining sample temperature during growth. Room CL measurement at room temperature can also be used as a means to check the quality of the substrate by comparing intensities of the GaN band edge energy peak and defect peaks. We have performed a detailed study of the factors influencing high temperature CL, and find the reproducibility of CL data and ability for fast CL scanning provide strong advantages for use in the growth of GaN films. CL could also be observed during growth using a ccd camera. This could be used to see temperature inhomogenaities, and potentially to map alloy composition fluctuations. Using tunable narrow bandpass optical filters, we can obtain a spatial/spectral map of sample CL. We will present CL images of samples at differing temperatures.This work was supported by the AFOSR MURI F49620-03-1-0330 and by ONR Grant N00014-02-1-0974.
12:00 PM - U3.4
Quantitative Study of Sub-monolayer growth of Ge(001) Homoepitaxy using Reflection High Energy Electron Diffraction.
Byungha Shin 1 , Michael Aziz 1
1 Division of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States
Show Abstract12:15 PM - U3.5
Reflection High-energy Electron Diffraction (RHEED) Pole Figures for Surface Texture Analysis.
Fu Tang 1 , Gwo-Ching Wang 1 2 , Toh-Ming Lu 1 2
1 Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, Troy, New York, United States, 2 Center for Integrated Electronics, Rensselaer Polytechnic Institute, Troy, New York, United States
Show AbstractF. Tang*, G.-C. Wang, and T.-M. LuDepartment of Physics, Applied Physics and AstronomyCenter for Integrated Electronics Rensselaer Polytechnic Institute, 110, 8th Street, Troy, New York 12180-3590.The preferred crystalline orientation, or texture, is a fundamental property of polycrystalline film and it directly controls many important physical properties such as optical, magnetic, mechanical, and electrical properties of the films. Texture formation is a very complex phenomenon. To date, the fundamental understanding of the atomistic mechanisms on the texture evolution still remains to be a challenging subject. This is largely due to the lack of experimental techniques to obtain detailed information on how the surface texture evolves at different stages of growth. The conventional x-ray pole figure gives an average texture of the entire thickness of the film since x-ray penetrates into the entire film and is not suitable for probing the surface texture during growth. Here we report the use of a conventional reflection high-energy electron diffraction (RHEED) technique to construct a surface pole figure, which can reveal the surface texture of polycrystalline films since electrons have only a very limited penetration depth. In this technique, the surface pole figure is constructed by recording multiple RHEED patterns as we rotate the substrate around the substrate normal. We show that very rich surface texture information can be obtained from the RHEED pole figures of Ru polycrystalline films composed of vertical or slanted nanorods. These Ru nanostructures were grown by the oblique angle deposition using a dc magnetron sputtering system. The vertical nanorods were formed by substrate rotation, while the slanted nanorods were formed with fixed substrate during deposition. From the analyses of constructed surface pole figures we found that the Ru vertical rods (~340 nm) display a simple vertical {10-10} fiber texture. However, Ru slanted nanorods show the complex multiple II-O textures including the co-existence of out-of-plane and in-plane preferred orientations. The evolution of the multiple II-O textures in slanted rods is further investigated by measuring the surface pole figures from the Ru slanted rods grown at various thicknesses (~30 nm, ~100 nm and ~400 nm). The technique allows one to extract information on the surface texture evolution and is readily adapted in a RHEED system. *F.T. is the recipient of the Harry Meiners Fellowship.This work has been supported in part by NSF NIRT (0506738).email address:
[email protected]12:30 PM - U3.6
In situ RHEED Monitoring of Epitaxial Film Growth on Continuously Moving Tape.
Vladimir Matias 1 , Ruud Steenwelle 1
1 , Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show Abstract12:45 PM - U3.7
Magnetic Interface Interactions in Cuprate-manganite Heterostructures and Superlattices.
Hanns-Ulrich Habermeier 1 , Christian Bernhard 2 , Jacques Chakhalian 1 , Soltan Soltan 1
1 , Max-Planck-Institute -FKF, Stuttgart Germany, 2 Physics, University of Fribourg, Fribourg Switzerland
Show AbstractU4: SPM
Session Chairs
Dave Blank
Hanns-Ulrich Habermeier
Tuesday PM, November 28, 2006
Room 300 (Hynes)
2:30 PM - **U4.1
Grain Growth and Film Growth Observed with Real-time, in-situ STM.
Marcel Rost 1
1 Leiden Institute of Physics, Leiden University, Leiden Netherlands
Show AbstractThe ever-growing variety of applications of film and thin film technology clearly demands fundamental research that links well known atomic processes, such as diffusion and nucleation, with the mesoscopic evolution of film properties, both during film growth and during a post deposition treatment (heating, stress, coating,...). Ideally, one would like to apply in-situ, real-time techniques that are nondestructive, surface sensitive and capable of resolving length scales that are relevant in the film evolution, which mostly requires Å resolution.The first real-time, in-situ movies on polycrystalline gold films will be shown that contain observations of grain growth and grain boundary diffusion as well as film growth, obtained with a variable-temperature Scanning Tunneling Microscope (STM).Atomic step resolution all over the film allowed us to identify the individual grains and, thus, also the grain boundaries. The special, thermal drift-compensated design of our home-built STM makes it possible to follow the same sample area of the film over large temperature intervals. In this way, we directly observed grain boundary diffusion and grain growth as we heated the film, which was created before by in-situ deposition at room temperature, up to 475 degrees C. As the film coarsened we observed unexpected changes in surface roughness: an initial decrease of the roughness was followed by a later increase. We can explain this behavior by correlating the surface structure of the film with the evolution of the grain structure of the film (the evolution of the grain and grain boundary configuration) [1].In order to further elucidate film growth, we evaporated several tens of monolayers of gold under grazing incidence on top of a well annealed polycrystalline gold film, while measuring with the STM. This enabled us to visualize film growth in real time.Analyzing the intermediate and developing film structures we succeeded in classifying the growth mode within the empirical film-growth structure-zone model introduced by Mochvan and Demchishin in 1969 [2]. Moreover, the direct observation provides us with atomic-scale insight in this classical growth mode: columnar grain growth is based on step-flow and spiral growth.In addition, by obtaining high resolution images on our polycrystalline gold films we even resolve the well-known Herringbone reconstruction. Using this reconstruction as an atomic scale stress sensor [3] we set the first steps to correlate the stress of individual grains with the specific geometry of the surrounding grainy structure.[1] M.J. Rost, D.A. Quist, J.W.M. Frenken; PRL 91, 026101 (2003)[2] Mochvan and Demchishin; Phys. Met. Metallurg. 28, 83 (1969)[3] U. Tartaglino, E. Tosatti, D. Passerone, and F. Ercolessi1; PRB 65, 241406 (2002)
3:00 PM - U4.2
Monitoring Oxide Thin Film Growth with in-situ Atomic Force Microscopy.
Joska Broekmaat 1 , Frank Roesthuis 1 , Alexander Brinkman 1 , Horst Rogalla 1 , Dave H.A. Blank 1 , Guus Rijnders 1
1 , Faculty of Science & Technology and MESA+ Institute for Nanotechnology, University of Twente Netherlands
Show AbstractComplex oxides exhibit various physical properties such as ferromagnetism, dielectricity, and superconductivity. The nature of these physical properties is determined by very small characteristic length scales. Future heteroepitaxial devices based on such oxides have great potential for applications provided that the growth can be controlled on an atomic level.Currently, in-situ growth morphology characterization is mostly performed by diffraction techniques such as Reflection High Energy Electron Diffraction (RHEED). We have now realized a system, in which Atomic Force Microscopy (AFM) can be performed during Pulsed Laser Deposition (PLD). Deposition and force microscopy are performed in one vacuum chamber and via a fast transfer (in the order of seconds) the surface of a sample can be scanned. In our system we take advantage of the pulsed deposition process, because microscopy measurements can be carried out between the pulses. This provides real-time morphology information on the microscopic scale during growth. The transfer mechanism allows switching between microscopy and deposition with a re-position accuracy of ±500 nm which gives new opportunities to study growth processes. This system is especially useful to study crystal growth, phase transitions, diffusion processes and nanoparticle formation. Furthermore, it will provide information if RHEED is not possible, for example during amorphous and polycrystalline growth. In this contribution, we will present the results obtained with a few model systems on oxide surfaces. We have used treated SrTiO3 (001) oxide substrates with 0.4 nm high substrate steps which are ideal for these experiments. Several materials are currently investigated, such as Au, SrRuO3, PbTiO3 and transparent conducting indium tin oxide. The in-situ AFM has been used to study the initial growth of these materials at various deposition conditions. The physical properties of these materials are correlated with the growth conditions, such as deposition pressure, fluency and substrate temperature. Besides showing the growth results obtained with the AFM, the latest equipment developments will be presented. To scan at elevated temperatures, small heaters have been developed. These small thermal mass heaters are designed in such a way to obtain stable monitoring settings at temperatures >973K in a high pressure environment or even ambient pressure. With high temperature microscopy, growth characterization at typical deposition conditions of complex oxides becomes feasible.
3:15 PM - U4.3
Ultra-low Attempt Frequencies for the Formation of Vacancies on III-V Semiconductor Surfaces Measured by in-situ Scanning Tunneling Microscopy.
Philipp Ebert 1 , Mariya Yurechko 1 , Knut Urban 1
1 Institut fuer Festkoerperforschung, Forschungszentrum Juelich, Juelich Germany
Show AbstractThe rates of atomic processes at growth interfaces, such as diffusion or the formation of vacancies, are classically described by an attempt frequency times the Boltzmann factor, containing the activation barrier and the temperature. The attempt frequencies are arise from vibrational excitations of the crystal lattice and thus are in the order of the Debye frequency, i.e. 1E12 to 1E13 Hz. We demonstrate, however, using variable temperature in-situ STM measurements of the formation kinetics of anion vacancies on p-type InP and GaAs (110) surfaces that the attempt frequency is in the order of 0.1 to 10 Hz, i.e. roughly 12 orders of magnitude smaller than expected. We show that the ultra-low activation frequencies arise from a rate limiting process, which is a one dimensional adatom diffusion mediating the desorption of anions as di-atom molecules.
3:30 PM - U4.4
In-situ Characterization of Iron Oxide Quantum Dots and Thin Film Growth using AFM.
Jessica Thery 1 , Michael Gordon 1 , Thierry Baron 1 , Catherine Dubourdieu 2 , Celine Ternon 1 , Hervé Roussel 2
1 , CEA, Grenoble France, 2 , LMGP, Grenoble France
Show Abstract3:45 PM - U4.5
in-situ Ultrahigh Vacuum Scanning Probe Microscopy Characterization of Ultra-Thin HfO2 Films on Initial Growth Stage
Lei Wang 1 , Kun Xue 1 , Jianbin Xu 1
1 Electronic Engineering, The Chinese University of Hong Kong, Hong Kong Hong Kong
Show AbstractHfO2 and Hf silicates are emerging as a potential replacement of SiO2 in CMOS technology. In this study, in-situ characterization of ultra-thin HfO2 on silicon substrate has been performed by ultrahigh vacuum scanning tunneling microscopy (UHVSTM) and conducting atomic force microscopy (UHV-c-AFM).UHVSTM is a powerful technique to investigate morphological and electronic structures of HfO2 films [1]. Furthermore, UHV-c-AFM can be used to differentiate the morphological and electronic convolution, and to study electrical degradation and leakage paths of ultrathin HfO2 in comparison with UHVSTM data. To study the initial growth stage, HfO2 films in different thickness varying from a sub-monolayer to a couple of monolayers were prepared by e-beam evaporation of Hf atoms and simultaneous oxidation on Si(111) under a base pressure less than 10-8 mbar. Sample post-annealing was in-situ conducted at different temperatures under UHV conditions, and STM images were subsequently acquired and analyzed. It is found that the top surface of hafnium oxide and/or silicate species first appeared as aggregated clusters on the stepped silicon surface after the initial deposition. With increasing the amount of the deposited species, the cluster size became larger. Further deposition progressively resulted in the formation of a continued HfO2 layer, and the stepped surface disappeared. Moreover, local electronic properties were examined on a nanometer scale, in aspects of current-voltage (I-V) and dI/dV characteristics. Detailed analyses of STM and AFM images indicate that the protrusions seen in STM images are likely correlated with the fixed charge sites [2]. And the evolution of the leakage current paths was directly observed by the UHV c-AFM.1.J. H. Lee and M. Ichikawa, J. Appl. Phys. 91, 5661 (2002).2.N. Miyataa, H. Ota and M. Ichikawa, Appl. Phys. Lett. 86, 112906 (2005).
4:30 PM - U4.6
In Situ Study of Optical Conductivity of Electroless Deposited Percolating Silver Films.
Stefan Kooij 1 , Anna Jo de Vries 1 , Agnes Mewe 1 , Herbert Wormeester 1 , Bene Poelsema 1
1 Solid State Physics, MESA+ Institute for Nanotechnology, University of Twente, Enschede Netherlands
Show AbstractConductive metal patterns can be fabricated through the selective electroless growth of silver on isolated nanocolloidal gold particles, deposited onto chemically functionalized substrates using microcontact printing. The transition from isolated nanoparticles to continuous, conducting silver films is characterised by a percolation threshold. Using spectroscopic ellipsometry in the visible and near-infrared spectral range on homogeneous particulate films, we have investigated this percolation threshold. From the ellipsometry spectra obtained as a function of electroless silver deposition times, the effective thickness as well as the complex dielectric function of the growing films are determined. For short deposition times, the optical spectra exhibit features characteristic of an effectively insulating, particulate layer. A maximum is observed in the imaginary part of the dielectric function, which shifts towards lower energy with increasing amounts of deposited silver. For thicker films, the appearance of a Drude-like free electron contribution to the optical spectra is exhibited by a strong increase of both the real and imaginary parts of the dielectric function towards lower energy. From the optical spectra, the percolation threshold is identified. The ellipsometry results are discussed in relation to DC conductivity measurements, which also reveal a percolation threshold. Furthermore, our conclusions and the advantages of our approach are discussed in relation to recently published in situ experiments, in which the growth of magnetron sputtered silver nanoparticles is monitored real-time yielding similar optical responses.
4:45 PM - U4.7
Atomic resolution STM of in-situ grown epitaxial SrRuO3 films: structure and electronic properties.
Junsoo Shin 1 2 , J. Zhou 3 , S. Kalinin 2 5 , V. Meunier 4 5 , E. Plummer 1 2 5 , A. Baddorf 2 5
1 Physics and Astronomy, University of Tennessee, Knoxville, Tennessee, United States, 2 Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 3 Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 5 Center for Nanophase Materials Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 4 Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
Show AbstractStrontium ruthenate, SrRuO3, is broadly used as a conductive electrode for oxide electronics due to good conductivity and relatively small lattice mismatch to SrTiO3 and many perovskite ferroelectrics. Understanding the interface structure and properties of oxide heterostructures requires the knowledge of the atomic structure of SrRuO3 prior to deposition of a second component. However, the perovskite structure of SrRuO3 precludes surface preparation through cleaving, which produces atomically flat surfaces for layered ruthenates. Here, we explore the atomic surface structure of SrRuO3 by growing the atomically flat epitaxial thin films on single-stepped (001) SrTiO3 by pulsed laser deposition (PLD) at 700 °C in 100 mTorr O2 pressure. The structure and electronic properties of films were characterized in-situ by scanning tunneling microscopy (STM) and low energy electron diffraction (LEED). Atomic resolution STM images of SrRuO3 films were observed at RT after the sample was annealed at ~550 °C in 1 torr oxygen pressure for 90 min following growth. The STM images demonstrate the atomic features and randomly ordered defects, similar to those observed in cleavable layered strontium ruthenates. Surfaces contain significant disorder, suggesting a liquid-like state for the surface. After higher annealing temperatures, more ordering of atomic rows was observed, which suggests the film surface has high mobility. After growth, a p(2x2) LEED pattern has been observed, which suggests that several possible crystal domain orientations of orthorhombic SrRuO3 with (2x1) structure on cubic SrTiO3 coexist in one thin film. The several possible models for defects including electronic phase separation and ordering of defect pairs are discussed. Research sponsored by the Division of Materials Sciences and Engineering, Office of Basic Energy Sciences, U.S. Department of Energy, under contract DE-AC05-00OR22725 with Oak Ridge National Laboratory, managed and operated by UT-Battelle, LLC.
5:00 PM - U4.8
In-situ Investigation of Surface Oxygen Vacancies in Perovskites
Fabio Miletto Granozio 1 , Gabriella De Luca 4 , Roberto Di Capua 2 , Nathascia Lampis 2 , Paolo Perna 3 , Milan Radovic 2 , Marco Salluzzo 1 , Umberto Scotti di Uccio 3 , Alessia Sambri 2 , Ruggero Vaglio 1 2
1 Coherentia, CNR-INFM, Napoli Italy, 4 Physics Department, Università di Salerno, Salerno Italy, 2 Physics Department, Università Federico II, Napoli Italy, 3 DiMSAT, Università di Cassino, Cassino (FR) Italy
Show AbstractOxygen nonstoichiometry plays a major role in the physics of complex oxides with perovskite structure, also because of its effect on carrier density. Such issue has been systematically investigated in the multichamber system recently set up in our labs, equipped with a RHEED/PLD chamber for thin film growth, and with two XPS/SPA-LEED, and STM/AFM chambers for sample characterization. Variable temperature electron diffraction and photoemission experiments, complemented by scanning probe analyses, were performed in our system in order to systematically address the influence of thermodynamic conditions on oxygen content. SrTiO3-x, in particular, was taken as a prototypical example of an oxygen deficient perovskite for most experiments. The configuration of oxygen vacancies in the terminating TiO2 layer appears to be influenced by the presence of surface steps.
5:15 PM - U4.9
In Situ Monitoring of the Stress Evolution During Electrochemical Deposition of Thin Films
Tianzhi Luo 1 , Robert Cammarata 1 2
1 Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland, United States, 2 Mechanical Engineering, Johns Hopkins university, Baltimore, Maryland, United States
Show AbstractThe stress evolution during electrochemical deposition of metals on amorphous substrates was monitored by an in situ, real time cantilever curvature measurement technique. The technique used is similar to that employed for in situ stress measurements performed during physical vapor deposition of thin films, but has been modified for optimal use in an electrochemical system. The electrodeposited films displayed Volmer-Weber island growth behavior, and exhibited a compression-tension-compression stress development that could be correlated with discrete island formation, island-coalescence, and post-coalescence growth stages, respectively. Under constant current conditions, the voltage transient displayed a corresponding three-stage character. Atomic force microscopy images confirmed that the microstructures of the films underwent three-dimensional island nucleation and growth. In the post-coalescence regime, interruption of the deposition resulted in an exponentially decreasing stress relaxation. The overall stress behaviors during growth and after the growth interruption were found to be very similar to that observed during physical vapor deposition of films on amorphous substrates. The experimental results will be analyzed in terms of recently proposed stress generation mechanisms.
5:30 PM - U4.10
Stress Evolution due to Island Coalescence During Film Growth.
Abhinav Bhandari 1 2 , Brian Sheldon 1 , Sean Hearne 2
1 Engineering, Brown University, Providence, Rhode Island, United States, 2 , Sandia National Labs, Albuquerque, New Mexico, United States
Show AbstractU5: Poster Session: In Situ Characterization
Session Chairs
Yves Chabal
Brian Stephenson
Wednesday AM, November 29, 2006
Exhibition Hall D (Hynes)
9:00 PM - U5.1
The Electronic Structure of 1,2-PCB10H11 Molecular Films: A Precursor to a Novel Semiconductor.
Snjezana Balaz 1 , Dimtcho Dimov 3 , Neil Boag 3 , Kyle Nelson 1 , Benjamin Montag 1 , Jennifer Brand 1 , Peter Dowben 2
1 College of Engineering and Technology, University of Nebraska-Lincoln, Lincoln, Nebraska, United States, 3 Chemistry and Nanotechnology, Institute for Materials Research, University of Salford, Salford United Kingdom, 2 Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, Nebraska, United States
Show AbstractThe band gaps and electronic structure of undoped films of molecular icosahedra of closo-1-phospha-2-carbadodecaborane (1,2-PCB10H11) are reported. 1,2-PCB10H11 adsorbs on Au and Ag substrates to generate molecular thin films with the Fermi level (chemical potential) placed closer to the lowest unoccupied molecular orbital than has been observed with closo-1,2-dicarbadodecaborane (1,2-C2B10H12, orthocarborane) adsorbed on Co, Cu or Ag. Both 1,2-PCB10H11 and 1,2-C2B10H12 molecular films exhibit an unoccupied molecular defect state above the Fermi level. The vibrational modes, observed in infra-red absorption, are close to the values expected for the isolated 1,2-PCB10H11 molecule. Consistent with the placement of the Fermi level in the molecular films, fabrication of heterojunction diodes from partially dehydrogenated 1,2-PCB10H11 indicates that the resultant PCB10Hx semiconductor film is more n-type than the corresponding boron carbide semiconductor formed from 1,2-C2B10H12, orthocarborane.
9:00 PM - U5.10
Structural Depinning of Ne Monolayers on Pb at T < 6:5 K
Lorenzo Bruschi 2 , Giovanni Fois 2 , A. Pontarollo 2 , Giampaolo Mistura 2 , Bruno Torre 1 , Francesco Buatier de Mongeot 1 , Corrado Boragno 1 , Renato Buzio 1 , Ugo Valbusa 1
2 Dipartimento di Fisica G.Galilei, Università di Padova , Padova Italy, 1 Dipartimento di Fisica, Università di Genova, Genova Italy
Show AbstractWe have studied the nanofriction of Ne monolayers with a quartz-crystal microbalance technique at temperatures below 6.5 K and in ultrahigh-vacuum conditions. Very homogeneous and smooth lead electrodes have been physically deposited on a quartz blank at 150 K and then annealed at room temperatures.With such a Pb-plated quartz-crystal microbalance, we have observed a pronounced depinning transition separating a low-coverage region, where the film is nearly locked to the oscillating electrode, from a high-coverage region characterized by slippage at the solid-fluid boundary. Such a behavior has been found to be very reproducible [1]. These data are suggestive of a structural depinning of the solid Ne film when it becomes incommensurate with the lead substrate, in agreement with the results of an extensive molecular-dynamics study. Further results acquired at higher temperatures and with different gases will be presented.[1] L. Bruschi et al. Phys. Rev. Lett. 96, 216101 (2006)
9:00 PM - U5.11
Retardation of Interfacial Layer Kinetics During Low Temperature UV Oxidation of Nitrogen Doped HfO2 Dielectrics.
Seungyoung Son 1 , Junnwoo Son 1 , Junghoon Jang 1 , Rajiv Singh 1
1 Materials Science & Engineering, University of Florida, Gaineville, Florida, United States
Show Abstract9:00 PM - U5.12
Characterization of Alumina Optical Waveguides Grown by Ion Beam Assisted Deposition for SPARROW Biosensors.
Pavan Samudrala 1 , Joshua Nightingale 1 , Min Lim 2 , Timothy Cornell 1 , Praneetha Poloju 1 , Dimitris Korakakis 1 , Lawrence Hornak 1
1 Lane Department of Computer Science and Electrical Engineering, West Virginia University, Morgantown, West Virginia, United States, 2 Bennett Department of Chemistry, West Virginia University, Morgantown, West Virginia, United States
Show AbstractOptical sensors based on evanescent wave coupling to an engineered biolayer provide an efficient approach to efficiently monitor the biolayer for affinity regulated binding. The SPARROW (Stacked Planar Affinity Regulated Resonant Optical Waveguide) biosensor design is an evanescent optical sensor of interest for its potential high sensitivity to effective refractive index change and simple stacked structure fabrication [1]. Uniform dielectric optical films with minimal surface roughness are required for such stacked waveguide structures, since the coupling characteristics used in signal transduction as well as biolayer nucleation and growth are dependent on the quality of the waveguides. In this study, alumina waveguides were chosen for their moisture stability and refractive index. Single mode waveguides are required for efficient device operation resulting in waveguides between 150nm and 250nm in thickness. Alumina optical films were fabricated on borofloat substrates using an ion assisted e-beam deposition technique. The optical and physical characteristics as well as the optical waveguide propagation loss were analyzed as a function of oxygen flow rate and drive current. The waveguides were characterized using ellipsometry, atomic force microscopy (AFM), prism coupler and waveguide loss measurements. Ellipsometer results indicate low global surface roughness with variation on the order of a nanometer over the 3 inch sample. The surface of the films was probed locally using Atomic Force Microscopy (AFM) and the dependence of surface roughness on the above parameters was observed. Over a range of few microns the RMS surface roughness is 0.7 nm with maximum peak to valley distance of 2 nm. The refractive indices of the films were found to vary from 1.62-1.64. Thickness or refractive index measurements were independently validated by comparison of modeled waveguide modal indices with those achieved from experimental prism coupler measurements. The waveguide optical loss was measured using the scattered power measurement technique employing a CCD camera and digital image processing techniques [2]. The optical losses were found to vary from 2db/cm to 6db/cm as a function of the drive current and oxygen flow rate. Reduced optical waveguide loss was achieved with low drive current and high flow rate. The influence of these factors on the optical film quality and the potential they hold for achieving further waveguide performance improvement is discussed.References:1)D.Lloyd, L.Hornak, S.Pathak, D.Morton, and I.Stevenson; “Application of Ion Beam Assisted Thin Film Deposition Techniques to the fabrication of Biosensor Chip With fieldability Potential for Important Biohazard Detection Applications” 47Annual Technical Conference Proceedings, Soc of Vac. Coaters, ISSN 0737-5921 (2004)2)Thomas A. Strasser and Mool C.Gupta, “Optical loss measurement of low-loss thin film waveguides by Photographic Analysis” Applied Optics, 31, 2041-2046 (1992).
9:00 PM - U5.13
Growth Kinetic Studies of Ge(001) Homoepitaxy by Pulsed Laser Deposition.
Lan Zhou 1 , Hua Zhou 1 , Randy Headrick 1
1 Physics, University of Vermont, Burlington, Vermont, United States
Show AbstractIt has been observed experimentally and theoretically that under certain conditions, Pulsed Laser Deposition (PLD) produces smoother thin films than thermal (molecular-beam-epitaxy and chemical vapor deposition) growth techniques. It is believed that the mechanism leading to the improved quality of surfaces is related to the two key characteristics in PLD: (1) pulsed mode of deposition (2) the enhancement of surface mass transport by energetic species. Each laser pulse ablates the target surface, and induces a high instantaneous flux of energetic ionic and neutral species (atoms, molecules, and small clusters) arriving on the substrates to form thin films. In this work, in situ characterization probes, such as the Langmuir probe and the time-resolved reflection high-energy electron diffraction (RHEED) with microsecond range temporal resolution and ex situ atomic force microscopy (AFM) are used to study the growth kinetics of pulsed laser deposited Ge (001) homoepitaxy. (1) Characterization of laser plume. In situ monitoring of the plume by Langmuir probe, the growth rate by the quartz crystal thickness monitor and the morphology information by ex situ AFM can give an insight into the correlation between the surface roughness of the thin films and the spatial, energy distribution of the ions and neutrals in the plume. It is observed that both the number and the average energy of the ions are strongly peaked about the target normal, while the neutrals have a wider distribution compared to the ions. The films are rougher when the substrates are positioned off-axis with respect to the target normal. (2) Interactions between the laser plume and the growing surface. As a consequence of the speed distribution of the particles in the plume, the deposition time is the order of tens of microseconds - fast ions arrive on the surface first then the slow neutrals. The time-resolved RHEED with microsecond temporal resolution can provide the whole picture of the formation of Ge epi-layer for individual laser shots during the deposition time and the time between two pulses.
9:00 PM - U5.14
In-situ Curvature Measurements During the Heteroepitaxy of Group-III-nitrides.
Armin Dadgar 1 3 , F. Schulze 1 , U. Haboeck 2 , F. Bertram 1 , J. Blaesing 1 , A. Diez 1 , T. Schenk 4 , K. Haberland 4 , A. Hoffmann 2 , T. Zettler 4 , C. Thomsen 2 , J. Christen 1 , A. Krost 1 3
1 FNW/IEP, Otto-von-Guericke-Universitaet magdeburg, Magdeburg Germany, 3 , AZZURRO Semiconductors AG, Magdeburg Germany, 2 Institut fuer Festkoerperphysik, TU-Berlin, Berlin Germany, 4 , Laytec GmbH, Berlin Germany
Show Abstract9:00 PM - U5.15
Bismuth Nanoparticles Formation by Electron Beam Irradiation in TEM.
Selene Sepulveda-Guzman 1 , Nora Elizondo-Villarreal 1 , Xiaoxia Gao 2 , Alejandro Torres-Castro 1 , Miguel Jose-Yacaman 1 3
1 Chemical Engineering, The University of Texas, Austin, Texas, United States, 2 Texas Materials Institute, The University of Texas, Austin, Texas, United States, 3 Texas Advanced Materials Center, The University of Texas, Austin, Texas, United States
Show Abstract9:00 PM - U5.16
Study on the Growth of Metal Oxide Nanowires by Synchrotron-based In-situ X-ray Diffraction
Guan Wang 1 , Xiao-Qing Yang 2 , Jonathan Hanson 2 , Xianrong Huang 1 , Michael Dudley 1
1 Materials Science Dept., Stony Brook University, Stony Brook, New York, United States, 2 Department of Chemistry, Brookhaven National Lab, Upton, New York, United States
Show Abstract9:00 PM - U5.17
High Speed Piezo Force Microscopy (4 seconds per image) for Dynamic Piezoactuation Mapping at the Nanoscale
Ramesh Nath 1 , David Shuman 1 , Bryan Huey 1
1 Institute of Materials Science, University of Connecticut, Storrs, Connecticut, United States
Show Abstract9:00 PM - U5.18
Electron Transport Properties of Organic Semiconductors Studied via Photoemission Spectroscopy and Current-Voltage Characteristics
Chih-I Wu 0
0 Electrical Engineering, National Taiwan University , Taipei, Taiwan, Taiwan
Show Abstract9:00 PM - U5.19
Photoemission Studies of Substitution Dependent of Electronic Structures and Transport Properties in Oligofluorene Thin Films
Chih-I Wu 2 1
2 Graduate Institute of Electro-Optical Engineering, National Taiwan University, Taipei Taiwan, 1 Electrical Engineering, National Taiwan University , Taipei, Taiwan, Taiwan
Show Abstract9:00 PM - U5.2
Passive Film Growth on Titanium Alloys in Simulated Body Fluid.
Julia Claudia Mirza Rosca 1 , Heinz Sturm 2 , Agustin Santana Lopez 1
1 Mechanical Engineering, Las Palmas de Gran Canaria University, Las Palmas de GC Spain, 2 BAM VI.2901, Federal Institute of Materials Research, Berlin Germany
Show Abstract9:00 PM - U5.20
In Situ UHV-TEM Observation of the Formation of Copper Oxide Nanostructure.
Li Sun 1 , Chao Fang 1 , Xuetian Han 1 , Alan McGaughey 2 , Judith Yang 1
1 Department of Materials Science and Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States, 2 Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania, United States
Show AbstractFor oxidation, most traditional methods focus on after-oxidation structures which cannot provide real time information about nucleation and initial growth of oxide. However, in situ UHV-TEM (ultra high vacuum-transmission electron microscopy) experiments can provide visual oxidation processes in real time and dynamic information of oxide islands at the nanometer scale. This experimental tool provides unique and critical data of these gas surface reactions in a wide pressure and temperature range needed for a fundamental understanding of the atomistic kinetics.We have used in situ ultra high vacuum transmission electron microscopy (UHV-TEM), to study the oxidation mechanism of Cu due to its wide industrial application. The initial stages of oxidation of Cu(100) at various temperatures (from 200 to 450 °C) and pressures (from 5×10-5 to 4×10-4 torr) has been examined. The quantitative measurements of the nucleation rate and saturation density versus pressure and temperature have been provided and the effect of electron beam exposure has been carefully considered. Comparison of our experimental data with simple nucleation rate theory demonstrates that there is qualitative agreement between nucleation rate theory and the initial stages of oxidation, but not quantitative. In particular, we find the correct asymptotic functional form is predicted, but with inconsistent exponents. Possible reasons for the quantitative disagreement and the implications to various oxidation theories are discussed.To further quantitative understanding of these nano-scale processes and the morphology evolution, an atomistic Kinetic Monte Carlo model, TFOx (Thin Film Oxidation), has been developed to simulate 2-D nanoscale oxidation behavior. By adjusting the input parameters, combined with different potential gradients, TFOx model has been used to study the dramatic effect of the attachment probabilities and the combined potential gradients on the island morphology. We are also transferring the old VB (Video Basic) version TFOx to the new C++ version to upgrade the speed of the program, make it more powerful and a new more efficient algorithm for the simulation of nanoscale oxidation process is also being developed in order to correlate better with experimental observations of oxide behavior produced during in situ oxidation of Cu thin films.In our future work, we will extend our researches to the initial stages of oxidation of metals with alloying elements, such as CuAu, CuTi, so that the results can be readily compared with Cu nano-oxidation.
9:00 PM - U5.21
Depth Profiling Raman Spectra as a New Approach to Study in-situ Growth of YBCO Films.
Maria Branescu 1 , Coralie Naudin 2 , Arturas Vailionis 3
1 , National Institute for Materials Physics, Bucharest Romania, 2 , Horiba Jobin Yvon, Ville Neuve d’Ascq France, 3 , Stanford University, Palo Alto, California, United States
Show Abstract9:00 PM - U5.3
Surface Reactions of Metal Catalysts for Carbon Nanotubes on an Oxide Thin Layer/Si Substrates Studied by in situ Micro X-ray Adsorption Spectroscopy using SPELEEM.
Fumihiko Maeda 1 , Hiroki Hibino 1 , Satoru Suzuki 1 , FangZhun Guo 2 , Yoshio Watanabe 2
1 NTT Basic Research Laboratories, NTT Corporation, Atsugi-shi, Kanagawa, Japan, 2 , The Japan Synchrotron Radiation Research Institute, Mikazuki-cho Sayo-gun, Hyogo, Japan
Show Abstract9:00 PM - U5.4
Investigation of the Directed Self-Assembly of Poly(L-lactic acid) and Poly(D,L-lactic acid) at the Air-Water Interface via Planar Array Infrared Spectroscopy
Young Shin Kim 1 , D. Bruce Chase 2 , John Rabolt 1
1 Materials Science and Engineering, University of Delaware, Newark, Delaware, United States, 2 Central Research and Development, DuPont Experimental Station, Wilmington, Delaware, United States
Show AbstractThe newly developed technique1 of planar array infrared (PA-IR) spectroscopy offers several advantages over Fourier transform infrared (FT-IR) methods such as ultrafast speed (<100 µsec) and excellent sensitivity. Recently, the spectral range of the PA-IR instruments has been extended2 to cover the methylene stretching (3200-2800 cm-1) and the IR fingerprint (2000-1000 cm-1) regions simultaneously. However, obtaining a spectrum in the range of 1800-1400 cm-1 at the air-water interface remains difficult due to poor IR reflectivity of water, the extremely low concentration of the ultra thin film, the interference of water at the interface and the presence of water vapor in the air. In this study, we report for the first time the PA-IR spectra (1900-1000 cm-1) of poly(L-lactic acid) (PLLA), poly(D,L-lactic acid) (PDLLA), and their mixtures during Langmuir compression on the surface of a deuterated water subphase. The results clearly show the formation of a PLA/PDLLA complx at the air-water interface with the corresponding presence of IR bands characteristic of the new conformation. 1 D. Elmore, M. W. Tsao, D. B. Chase and J. F. Rabolt, Applied Spectroscopy 2002, 56, 1452 C. Pellerin, C. Snively, Y. Liu, D. B. Chase and J. F. Rabolt, Applied Spectroscopy 2004, 58, 639-646
9:00 PM - U5.5
The Influence of Oxygen Diffusion on Residual Stress for Tantalum Thin Films.
Ming-Hsin Cheng 1 , Tsung-Chien Cheng 1 , Wen-Jun Huang 1 , Mao-Nan Chang 1 , Eddy-Jones Chung 2
1 , National Nano Device Laboratories, Hsinchu Taiwan, 2 , PANalytical, Taipei Taiwan
Show Abstract9:00 PM - U5.6
Characterization of High k Dielectric Leakage by Non-contact Corona Kelvin Based Metrology.
Yunjung Jee 1 , Mi-sung Lee 1 , So-Yeon Yun 1 , Han-Soo Cho 1 , ChungSam Jun 1 , Tae-Sung Kim 1
1 , Samsung Electronics, Hwasung, Gyeonggi-do, Korea (the Republic of)
Show Abstract9:00 PM - U5.7
In-situ X-ray Characterization of Nucleation, Growth, and Phase Stability of Magnetron Sputtered Tin+1AlNn Mn+1AXn Phase Thin Films.
Manfred Beckers 1 3 , Norbert Schell 2 3 , Rui Martins 2 3 , Wolfhard Möller 3 , Lars Hultman 1
1 Thin Film Physics Division, Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping Sweden, 3 Institute of Ion Beam Physics and Materials Research, Forschungszentrum Rossendorf, Dresden Germany, 2 ROBL-CRG , ESRF, Grenoble France
Show Abstract9:00 PM - U5.8
Electrically Guided Assembly of Planar Colloidal Crystals.
Keqin Zhang 1 , Xiang-Yang Liu 1
1 , National University of Singapore, Singapore Singapore
Show Abstract9:00 PM - U5.9
Kikuchi Features as the Origin of the Phase Shift of RHEED Intensity Oscillations During Homoepitaxy by MBE.
Byungha Shin 1 , John Leonard 2 , James McCamy 1 , Michael Aziz 1
1 Division of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States, 2 Materials Science and Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
Show AbstractReflection High Energy Electron Diffraction (RHEED) is routinely used during epitaxial growth to monitor the surface structure and the quality of a film. Despite the widespread usage of RHEED over many years, there still remain fundamental questions unanswered with regard to the interpretation of RHEED measurements. One of these issues is the phase shift of the RHEED intensity oscillations upon changing the incidence angle of electron beams. Therefore, we have conducted a systematic investigation of the phase shift of the RHEED intensity oscillations during homoepitaxy of Ge(001) by molecular beam epitaxy for a wide range of diffraction conditions. Our results show that for small incidence angles with a beam azimuth several degrees away from crystallographic symmetry directions, the phase stays the same; it starts to shift once the (004) Kikuchi line appears in the RHEED pattern. Moreover, under some conditions we observe the oscillations from only the Kikuchi feature and not from the specular spot, and the oscillatory behavior of the Kikuchi feature is almost out of phase with that of the specular spot. All these results convincingly demonstrate that the phase shift is caused by the interference of the specular spot by the Kikuchi features. The lesson that can be learned from our study is that in order to use the RHEED specular intensity oscillation to learn about surface morphology, one must be extremely careful that the RHEED measurements be conducted under conditions where the influence of the Kikuchi features is minimal.
Symposium Organizers
Vladimir Matias Los Alamos National Laboratory
Robert Hammond Stanford University
Guus Rijnders University of Twente
Darrell Schlom The Pennsylvania State University
U6: X-ray I
Session Chairs
Orlando Auciello
Tom Myers
Wednesday AM, November 29, 2006
Room 300 (Hynes)
9:30 AM - **U6.1
X-Ray Standing Wave Imaging of Atoms at Interfaces
Michael Bedzyk 1 2 , Chang-Yong Kim 1
1 Materials Science, Northwestern University, Evanston, Illinois, United States, 2 , Argonne National Laboratory, Argonne, Illinois, United States
Show Abstract We have developed an x-ray synchrotron based strategy for determining the element-specific atomic-scale structure of crystalline interfaces. When combined with XPS and AFM we gain chemical sensitivity and nano-scale morphology. Using conventional X-ray standing wave (XSW) analysis (based on single-crystal Bragg diffraction), the hkl Fourier component for a x-ray fluorescence-selected atomic species is measured. By summing together several such hkl Fourier components, it is possible to directly generate a 3D, direct-space, 0.5 Å resolution, image of the atomic distribution with respect to the bulk crystal primitive unit cell. We have recently demonstrated this for the cases of bulk impurity atoms [1], cations adsorbed at the aqueous / oxide interface [2], metallic atoms at semiconductor surfaces [3], and oxide supported catalysts [4]. This new model-independent XSW imaging approach proves to be very insightful for complex cases in which atoms occupy unknown multiple crystallographic sites. In comparison to direct-methods based on conventional diffraction, the Fourier inversion process for generating an XSW image is much simpler, since the hkl phase (as well as amplitude) of each Fourier component is directly measured. Based on these model-independent XSW atomic images, we then develop models to refine the data analysis into 0.05 Å resolved atomic lattice positions that are used to measure effects such as strain. As part of our procedure, we calibrate the XRF yields to achieve a quantitative measure of the occupation fraction (stoichiometry) as well as the occupation lattice site for each XRF detectable species. In separate XPS measurements, we correlate this structural information with the chemical state of the adsorbed species. We are now applying this method to ALD and MBE grown oxide/oxide, metal/oxide and oxide/semiconductor heteroepitaxial structures and observing how the atoms at the interface redistribute after oxidation and reduction processes. In combination with AFM we are also correlating the atomic-scale and nano-scale structure of metal nanocrystals grown on oxide surfaces. Future directions include microbeam in situ real-time studies of growth and ferroelectric polarity switching.[1] L. Cheng, P. Fenter, M. J. Bedzyk, N. C. Sturchio, Phys. Rev. Lett. 90, 255503-1 (2003).[2] Z. Zhang, P. Fenter, L. Cheng, N. C. Sturchio, M. J. Bedzyk, M. L. Machesky, D. J. Wesolowski, Surf. Sci. Lett., 554(2-3) L95 (2004).[3] A.A. Escuadro, D.M. Goodner, J.S. Okasinski, M.J. Bedzyk, Phys. Rev. B, 70 235416-1-7 (2004).[4]. C.-Y. Kim, J.W. Elam, M. J. Pellin, D.K. Goswami, S. T. Christensen, M. C. Hersam, P. C. Stair, M. J. Bedzyk, J. Phys Chem. B (in press) (2006).
10:00 AM - **U6.2
Synchrotron-Based In Situ X-ray Scattering and Reflectivity Studies of Pulsed Laser Deposition.
Joel Brock 1 2
1 Cornell Center for Materials Research, Cornell University, Ithaca, New York, United States, 2 School of Applied and Engineering Physics, Cornell University, Ithaca, New York, United States
Show AbstractX-ray scattering and reflectivity have been effectively used to measure the atomic-scale structure of surfaces and interfaces for several decades. Modern synchrotron X-ray facilities now deliver sufficient flux to make time-resolved measurements on a wide variety of systems feasible. In particular, time-resolved X-ray structural studies of Pulsed Laser Deposition of SrTiO3 [1-4] have recently been shown to provide detailed insight into the atomic-scale growth mechanisms. In addition to determining the growth mode, the surface/interface roughness, and the film thickness, some of the dynamics of the energetic collisions and the details of the subsequent kinetic relaxation are experimentally accessible. Epitaxial films grown by PLD are now of high enough quality that standard descriptions in terms of continuous surface roughness are no longer adequate to describe the X-ray data accurately[5]. The time-resolved data sets provide both guidance for developing and mechanisms to test a new generation of multi-scale models.1. Fleet, A., D. Dale, Y. Suzuki, and J.D. Brock, Observed Effects of a Changing Step-Edge Density on Thin-Film Growth Dynamics. Physical Review Letters, 2005. 94: p. 036102.1-4.2. Fleet, A., D. Dale, A.R. Woll, Y. Suzuki, and J.D. Brock, Multiple Time Scales in Diffraction Measurements of Diffusive Surface Relaxation. Physical Review Letters, 2006. 96(5): p. 055508.1-4.3. Willmott, P.R., R. Herger, C.M. Schleputz, D. Martoccia, and B.D. Patterson, Energetic Surface Smoothing of Complex Metal-Oxide Thin Films. Physical Review Letters, 2006. 96(17): p. 176102.1-4.4. Tischler, J.Z., G. Eres, B.C. Larson, C.M. Rouleau, P. Zschack, and D.H. Lowndes, Nonequilibrium Interlayer Transport in Pulsed Laser Deposition. Physical Review Letters, 2006. 96(22): p. 226104.1-4.5. Dale, D., A. Fleet, J.D. Brock, and Y. Suzuki, X-ray scattering from real surfaces: discrete and continuous components of roughness. Submitted to Physical Review B, 2006.
10:30 AM - U6.3
Determining the Growth Mode of SrTiO3 (001) Homoepitaxy via Pulsed Laser Deposition using In Situ X-Ray Reflectivity.
John Ferguson 1 3 , Gokhan Arikan 1 2 , Aram Amassian 1 3 , Darren Dale 4 , Arthur Woll 4 , Joel Brock 1 2
1 Cornell Center for Materials Research, Cornell University, Ithaca, New York, United States, 3 Department of Materials Science and Engineering, Cornell University, Ithaca, New York, United States, 2 School of Applied and Engineering Physics, Cornell University, Ithaca, New York, United States, 4 Cornell High Energy Synchrotron Source, Cornell University, Ithaca, New York, United States
Show AbstractHomoepitaxial SrTiO3 thin films were grown on SrTiO3 (001) via Pulsed Laser Deposition. The growth was monitored in real-time by in situ X-ray reflectivity measurements at the anti-Bragg point of the (00L) Crystal Truncation Rod. Due to the need for a large X-ray intensity to monitor the anti-Bragg position, these experiments were performed at the Cornell High Energy Synchrotron Source (CHESS). We investigated the role of laser repetition rate and substrate temperature for films deposited at an O2 background pressure of 10-6 Torr. We observe a transition in growth mode from layer-by-layer to step-flow with increasing temperature while keeping laser repetition rate constant. We observed a similar transition in the growth mode when the substrate temperature is held constant and the laser repetition rate is decreased. The surface miscut is also observed to play a similar role. We show that this transition can be described in terms of the deposition rate, diffusion length, and step spacing.
10:45 AM - U6.4
Effects of Concurrent Discrete and Continuous Roughness on Surface Scattering.
Darren Dale 1 4 5 , Aaron Fleet 2 4 6 , Joel Brock 2 4 , Yuri Suzuki 3
1 Department of Materials Science and Engineering, Cornell University, Ithaca, New York, United States, 4 Cornell Center for Materials Research, Cornell University, Ithaca, New York, United States, 5 Cornell High Energy Synchrotron Source, Cornell University, Ithaca, New York, United States, 2 School of Applied and Engineering Physics, Cornell University, Ithaca, New York, United States, 6 , Lincoln Laboratory, Lexington, Massachusetts, United States, 3 Department of Materials Science and Engineering, UC Berkeley, Berkeley, California, United States
Show AbstractIncoherent surface scattering yields a statistical description of the surface due to the ensemble averaging over many independently sampled volumes. Depending on the state of the surface and the direction of the scattering vector relative to the surface normal, the height distribution is discrete, continuous, or a combination of the two. We present a treatment for the influence of multimodal surface height distributions on Crystal Truncation Rod scattering. The effects of a multimodal height distribution are especially evident during in-situ monitoring of layer-by-layer thin films growth via pulsed laser deposition. We model the total height distribution as a convolution of continuous and discrete components, resulting in a broadly applicable paramaterization of surface roughness which can be applied to other scattering probes such as electrons and neutrons. We will present the application of this analysis to describe our experimental studies of <001> SrTiO3 annealing and homoepitaxial growth.
11:00 AM - U6: X-ray I
BREAK
11:30 AM - U6.5
Interlayer Transport in Pulsed Laser Deposition of SrTiO3 Studied by Time-Resolved Surface X-Ray Diffraction
Gyula Eres 1 , J. Tischler 1 , B. Larson 1 , C. Rouleau 1 , D. Lowndes 1 , P. Zschack 2
1 Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 2 Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois, United States
Show AbstractFilm growth in pulsed laser deposition (PLD) occurs from the energetic plume of material ejected from a solid target by pulsed laser ablation. The plume consists of a complex mixture of neutral and ionized atoms, molecules, and even small clusters with kinetic energies ranging from thermal to a few hundred eV. The extra kinetic energy provides a transient (nonequilibrium) enhancement of surface mobility and is believed to alter the nucleation and growth of thin films. However, the mechanisms by which the transient mobility enhancement affect the growth kinetics are not well understood. We use time-resolved surface x-ray diffraction (SXRD) measurements with microsecond range resolution to study the role of nonequilibrium processes in PLD of SrTiO3. The use of x-ray diffraction greatly simplifies growth kinetics studies because in the kinematic limit the x-ray intensity changes correspond directly to coverage changes. Rather than using a transport model to fit the data, we instead analyze the intensity transients using an approach that allows direct determination of the transient surface coverages from the diffraction intensities [1]. The initial change in the coverage shows the fraction of the pulse instantaneously forming on each layer, and the time evolution of the coverages shows the amount of material transferred from the top of the islands into the growing layer. This analysis reveals that the energy-enhanced interlayer transport occurs on a time scale of microseconds or less and it dominates layer filling in PLD growth. A much smaller fraction of material, which is governed by the dwell time between successive laser shots is transferred by slow, thermally driven interlayer transport processes. [1] J.Z. Tischler, Gyula Eres, B.C. Larson, C.M. Rouleau, P. Zschack, and D.H. Lowndes, Phys. Rev. Lett. 96, 226104 (2006).
11:45 AM - U6.6
Time-resolved X-ray Studies of the Energetic Mechanisms Operant During Pulsed Laser Deposition of SrTiO3.
Gokhan Arikan 1 2 , John Ferguson 1 3 , Aram Amassian 1 3 , Darren Dale 4 , Arthur Woll 4 , Joel Brock 1 2
1 Cornell Center for Materials Research, Cornell University, Ithaca, New York, United States, 2 School of Applied and Engineering Physics, Cornell University, Ithaca, New York, United States, 3 Department of Materials Science and Engineering, Cornell University, Ithaca, New York, United States, 4 Cornell High Energy Synchrotron Source, Cornell University, Ithaca, New York, United States
Show AbstractHomoepitaxial SrTiO3 thin films were grown on SrTiO3 (001) via Pulsed Laser Deposition in three different growth modes: 3D, layer-by-layer, and step-flow. The instantaneous X-ray diffraction intensity drop due to the arrival of a pulse of material at the surface is monitored in real-time at the anti-Bragg position on the (00L) Crystal Truncation Rod. Due to the need for a large X-ray intensity to monitor the anti-Bragg position, these experiments were performed at the Cornell High Energy Synchrotron Source (CHESS). The instantaneous change in reflected intensity ΔI/I contains information on the fast smoothening mechanisms which occur during the impact[1, 2]. By varying temperature, repetition rate, miscut, and the variation in surface morphology, we are able to probe the nature of the dynamics of the energetic collision by monitoring the changes in ΔI/I.1. Fleet, A., D. Dale, Y. Suzuki, and J.D. Brock, Observed Effects of a Changing Step-Edge Density on Thin-Film Growth Dynamics. Physical Review Letters, 2005. 94: p. 036102.1-4.2. Fleet, A., D. Dale, A.R. Woll, Y. Suzuki, and J.D. Brock, Multiple Time Scales in Diffraction Measurements of Diffusive Surface Relaxation. Physical Review Letters, 2006. 96(5): p. 055508.1-4.
12:00 PM - U6.7
Real-time Synchrotron X-ray Studies of Ga Droplet and GaN Quantum Dot Formation by Droplet Heteroepitaxy on C-plane Sapphire.
Yiyi Wang 1 , Ahmet Ozcan 1 , Karl Ludwig 1 , Anirban Bhattacharyya 2 , Theodore Moustakas 2
1 Physics, Boston University, Boston, Massachusetts, United States, 2 Electrical and Computer Engineering, Boston University, Boston, Massachusetts, United States
Show Abstract12:30 PM - U6.9
In-Situ X-Ray Studies of Oxygen Adsorption and Ordering on Cu (001).
Dillon Fong 1 , Jeffrey Eastman 1 , Guangwen Zhou 1 , Paul Fuoss 1 , Peter Baldo 1 , Loren Thompson 1 , Lynn Rehn 1
1 Materials Science Division, Argonne National Laboratory, Argonne, Illinois, United States
Show AbstractMany important oxidative reactions, such as CO oxidation, take place on metal surfaces at high temperatures and partial pressures. Understanding the atomic processes involved in these catalyzed reactions are of great importance and may be achievable by observations of the adsorbate-induced surface structure under temperatures and pressures relevant to working catalysts. Many of the prior studies, however, have only considered quenched-in structures with no dynamic interaction between the metal surface and the gas phase. This presentation describes in-situ synchrotron x-ray studies of the Cu (001) surface as a function of pO2, the oxygen partial pressure, and temperature. We utilize a controlled-flow reaction chamber specially constructed to mount onto an eight-circle diffractometer at the Advanced Photon Source. The chamber allows the flow of oxygen, hydrogen, and argon mixtures with pO2 ranging from 760 to 1×10-12 Torr and sample temperatures variable from 25 to 1000 °C. After reaching a critical pO2, oxygen adsorbs onto the initially clean Cu (001) surface, resulting in the rapid nucleation and growth of c(2×2)-O domains. Domain formation is concurrent with a small in-plane surface contraction and a large out-of-plane surface expansion associated with a compressive adsorbate-induced surface stress. The often reported (2√2×√2)R45 reconstruction is observed only below ~ 150 °C. Relationships between the different surface structures, subsurface oxygen, surface stress, and surface reactivity will be discussed.
12:45 PM - U6.10
Real-time Study of Low-energy Ion Bombardment-induced Surface Smoothing on Nanocorrugated Sapphire
Hua Zhou 1 , Lan Zhou 1 , Randall Headrick 1 , Gozde Ozaydin 2 , YiYi Wang 2 , Karl Ludwig Jr. 2
1 Physics, University of Vermont, Burlington, Vermont, United States, 2 Physics, Boston University, Boston, Massachusetts, United States
Show AbstractSurface morphology modification by low-energy ion bombardment is widely used in many thin film techniques such as sputter deposition, ion-beam-assisted growth and ion polishing, in order to obtain smooth surfaces desirable for device applications. Under certain circumstances, ion bombardment on surfaces is also known to produce 2-D (ripples or wires) and 1-D (dot) structures by a self-organization process that arises from a competition of a roughing instability mechanism and surface relaxation. Knowledge of the mechanisms which govern those surface processes is very crucial to engineer technologically significant surface morphologies at the submicron or nano-scale in a more controlled way. Recently, the fast-growing advances in synchrotron x-ray scattering and detector techniques have enabled detailed investigations into the surface kinetics during ion bombardment. In this work, a study of surface smoothing on nanocorrugated sapphire surfaces by low-energy ion bombardment at normal incidence will be presented. Real time characterization by synchrotron grazing incidence small angle x-ray scattering for the dependence of smoothing rate on ion energy and wavelength of sapphire ripples is performed. A ripple amplitude displays a classic behavior of profile-preserving exponential decay with time upon ion irradiation. The dependence of smoothing rate on ion energy and wavelength is discussed with existing surface smoothing mechanisms. The wavelength dependence exhibits a power law behavior with exponential close to 2 instead of 4, which suggests a dominant smoothing mechanism related to ion impact induced lateral mass redistribution for near normal incidence condition. The appearance of multiple smoothing rate constants at high temperature is thought to be relative with emerging atomic steps after surface recrystallization.
U7: X-ray II
Session Chairs
Michael Bedzyk
Joel Brock
Wednesday PM, November 29, 2006
Room 300 (Hynes)
2:30 PM - **U7.1
In-Situ X-ray Studies of Metal-Organic Chemical Vapor Deposition.
Brian Stephenson 1 , R. Wang 1 , D. Fong 1 , F. Jiang 1 , S. Streiffer 1 , J. Eastman 1 , P. Fuoss 1 , K. Latifi 2 , Carol Thompson 2
1 Materials Science Division, Argonne National Laboratory, Argonne, Illinois, United States, 2 Department of Physics, Northern Illinois, DeKalb, Illinois, United States
Show AbstractX rays provide an excellent atomic-scale probe of non-vacuum processes such as metal-organic chemical vapor deposition (MOCVD). We have developed a growth chamber mounted on a z-axis surface diffractometer optimized for these studies at beamline 12-ID-D of the Advanced Photon Source. This talk will give examples of our in situ synchrotron x-ray scattering and fluorescence studies of processes occurring during MOCVD growth, and at surfaces and interfaces in the MOCVD environment. We have been studying growth of multicomponent oxide and nitride materials. In particular, we report studies of the initial stages of epitaxial growth of Pb(Zr,Ti)O3 (PZT) films on (001) SrTiO3 using simultaneous in situ grazing-incidence x-ray scattering and fluorescence. We observe that the Zr content increases dramatically as strain relaxation occurs, resulting in compositional non-uniformity in the growth direction. These results can be understood based on the interplay between the composition dependence of the lattice parameter, strain relaxation, and growth, consistent with the thermodynamic model of “lattice pulling” developed to describe growth of epitaxial semiconductor alloy films [1]. Such non-uniformity is especially critical in ferroelectric thin films, since both film strain and composition strongly influence ferroelectric properties. In situ x-ray scattering also provides a powerful tool for observing the phase transition, domain structure, and surface structure of ultrathin ferroelectric films [2,3]. We will also report examples of recent results in this area.[1] F.C. Larché and J. W. Cahn, J. Appl. Phys. 62, 1232 (1987)[2] D.D. Fong et al., Science 304, 1650 (2004)[3] D.D. Fong et al., Phys. Rev. Lett. 96, 127601 (2006)
3:00 PM - U7.2
In-situ Synchrotron X-ray Diffraction during Pulsed Laser Deposition of Complex Oxides.
Guus Rijnders 1 , Arjen Janssens 1 , Vedran Vonk 1 , Mark Huijben 1 , Sybolt Harkema 1 , Dave Blank 1 , Heinz Graafsma 2 , Paul Tinnemans 3 , Elias Vlieg 3
1 MESA+ Institute for Nanotechnology & Faculty of Science and Technology, University of Twente, Enschede Netherlands, 2 , European Synchotron Radiation Facility, Grenoble France, 3 Solid State Chemistry, Radboud University, Nijmegen Netherlands
Show Abstract3:15 PM - U7.3
Early-Stage Oxidation Behavior Of Cu-Ni Alloys
Jeffrey Eastman 1 , Dillon Fong 1 , Paul Fuoss 1 , Peter Baldo 1 , Guangwen Zhou 1 , Lynn Rehn 1 , Loren Thompson 1
1 Materials Science Division, Argonne National Laboratory, Argonne, Illinois, United States
Show AbstractIn situ synchrotron x-ray techniques are ideal for providing insight into the oxidation behavior of metals and alloys. Here, we present results from an in situ study of the early-stage processes during oxidation of (001) single crystal Cu-Ni alloys, of interest, for example, as catalysts of a number of important chemical reactions. Grazing incidence x-ray diffraction observations in controlled, elevated temperature oxidizing conditions reveal that, with increasing oxygen partial pressure (pO2), epitaxial cube-on-cube-oriented NiO islands form first, followed by other epitaxial orientations of NiO. As the pO2 continues to be increased, epitaxially-oriented Cu2O islands will also eventually nucleate and grow. In some cases, evidence is seen for the formation of internal, as well as surface oxide islands. Total reflection x-ray fluorescence observations provide a complementary sensitive measure of the changes in the alloy surface composition in response to changes in the composition of the gas environment in contact with the sample. Evidence is seen for Ni surface segregation under intermediate pO2 conditions where NiO, but not Cu2O nucleates and grows. In addition to describing the oxidation behavior of Cu-Ni alloys as functions of alloy composition, temperature, and pO2, we also will discuss the possible effects of the presence of Cu2O islands or oxygen-induced surface structure(s) on the activity of Cu or Cu-Ni surfaces in catalyzing the methanol oxidation reaction.
3:30 PM - U7.4
Time-resolved X-ray Reflectivity Study of Interfacial Reactions and Intermetallic Formation During In-situ Constant Heat-treatment.
Marta Gonzalez-Silveira 1 , Javier Rodriguez-Viejo 1 , M.Teresa Clavaguera-Mora 1 , Thierry Bigault 2
1 Dept. of Physics, Universitat Autonoma de Barcelona, Bellaterra, Barcelona, Spain, 2 , Institut Laue-Langevin, Grenoble France
Show Abstract3:45 PM - U7.5
In situ Characterization of the Dynamics of Pentacene Growth.
Alex Mayer 1 , Aram Amassian 1 , George Malliaras 1
1 , Cornell University, Ithaca, New York, United States
Show Abstract4:00 PM - U7: X-ray II
BREAK
4:30 PM - U7.6
Real-Time In-Situ X-Ray Diffraction Studies of Self-Propagating Exothermic Reactions in Nanostructured Reactive Multilayer Foils.
Jonathan Trenkle 1 , Lucas Koerner 2 , Harish Nathani 1 , Mark Tate 2 , Sol Gruner 2 3 , Timothy Weihs 1 , Todd Hufnagel 1
1 Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland, United States, 2 Department of Physics, Cornell University, Ithaca, New York, United States, 3 Cornell High Energy Synchrotron Source, Cornell University, Ithaca, New York, United States
Show AbstractReactive multilayer foils are energetic materials comprised of alternating nanoscale layers of materials that can sustain a self-propagating exothermic reaction. The reaction characteristics, including the maximum temperature, heat released, and speed of propagation, can be precisely controlled by appropriate design of the multilayer architecture. However, the characteristic length and time scales make studying the reaction itself a significant challenge. For instance, the reaction zone is typically ~100 μm wide and propagates at ~1 m s-1, reaching temperatures in excess of 1500 oC in less than 100 μs, followed by rapid cooling. One aspect that makes these reactions interesting from a scientific point of view is that the rapid heating and cooling may provide kinetic contraints, which would alter the phase transformations relative to those observed in a slower reaction (e.g. by annealing) in the same multilayer system.We have studied phase evolution in-situ during self-propagating reactions in both Al/Ni and Zr/Ni reactive multilayers by means of x-ray diffraction using a pixel array detector at the Cornell High Energy Synchrotron Source. The time resolution (≈50 μs) and spatial resolution (≈60 μm) of the measurements was sufficient to allow us to observe the phase transformation sequence in detail. In both reactive systems, the initial reaction occurs within the first 0.1 ms and forms one or more of the final phases without any metastable intermediate phases being observed. For example, Al/Ni multilayers with an overall composition of Al3Ni2 first form the cubic intermetallic AlNi equilibrium phase, followed by trigonal Al3Ni2 some 47 ms later during cooling. Similarly, in Zr/Ni reactive foils, orthorhombic ZrNi forms prior to the detection of tetragonal Zr2Ni. In this presentation, we will briefly describe the details of the experiments before discussing the kinetics of the phase evolution in Al/Ni and Zr/Ni reactive multilayer foils.
4:45 PM - U7.7
Significant Shift of Phase Transition Temperature of Strained SrRuO3 Thin Films.
Kyoungjin Choi 1 , S. Baek 1 , H. Jang 1 , L. Belenky 1 , C. Eom 1
1 Materials Science and Engineering, University of Wisconsin - Madison, Madison, Wisconsin, United States
Show Abstract5:00 PM - U7.8
Band Alignment in Alternative CMOS Gate Stacks
Eric Garfunkel 1 , Sylvie Rangan 2 , Eric Bersch 2 , Ozgur Celik 1 , Chien-lan Hsueh 2 , Robert Bartynski 2
1 Chemistry, Rutgers University, Piscataway, New Jersey, United States, 2 Physics, Rutgers, Piscataway, New Jersey, United States
Show AbstractThe materials and electrical properties of high-k dielectrics, metal electrodes and alternative semiconductors are under intense scrutiny because of their potential to offer greatly increased performance in CMOS devices. The band alignment at individual interfaces as well as across multilayer stacks is critical to ensure proper device performance including low leakage currents and appropriate threshold voltages. An understanding of the relevant energies, particularly the role played by interface dipoles, may enable the tuning of band offsets at interfaces. Conduction and valence band edge definition, band gap and defect determination, and the proper extraction of an “effective” work function are complex and a consensus has yet to emerge in the materials and CMOS device community. In this presentation, we outline some of our recent work on the characterization of the electronic structure (DOS, band offsets, etc.) in the various layers of complex gate stacks. Results of studies using direct, inverse and internal photoemission will be presented for a series of structures comprised of different metals (Ru, Al, Ti), dielectrics (HfO2, SiO2 and HfxSi1-xO2) and semiconductors (Si, Ge and GaAs). The band offsets we measure for the metal/oxide and oxide/semiconductor interfaces are, to first order, in agreement with a modified Schottky-Mott model which treats the interfaces with bulk properties. But as expected, the results reveal much more complicated interfaces, and in particular strong effects on the chemistry of the entire stacks upon metal deposition. Both Ru and Al induce an energy shift of the core, valence and conduction band levels. Ru stays metallic upon deposition on the oxide, whereas Al is shown to become oxidized. We show that the source of oxygen can be the dielectric or the interface layer between the substrate and dielectric. We also present complimentary analysis using ion scattering, electrical methods, electron and scanning probe microscopy and theory.
Symposium Organizers
Vladimir Matias Los Alamos National Laboratory
Robert Hammond Stanford University
Guus Rijnders University of Twente
Darrell Schlom The Pennsylvania State University
U8: Optical
Session Chairs
Thursday AM, November 30, 2006
Room 300 (Hynes)
10:00 AM - **U8.1
In situ Infrared Absorption Spectroscopy for Thin Film Growth by Atomic Layer Deposition.
Yves Chabal 1
1 Laboratory for Surface Modification, Rutgers University, Piscataway, New Jersey, United States
Show AbstractAtomic Layer Deposition (ALD) is a particularly appealing growth method to deposit ultra-thin films at relatively low temperatures with high conformality. However, the growth mechanisms impacting both the film quality and film/substrate interface are not well understood for lack of in situ chemical characterization. We have developed an ALD reactor equipped with in-situ IR spectroscopy capabilities to investigate film growth and interface formation. Our studies have focused on the growth of high-κ dielectrics such as Al2O3 and HfO2 on silicon and germanium substrates, and the influence of surface chemical pre-treatment and post-annealing on the formation on interfacial layers and film quality.
10:30 AM - U8.2
Using Multi Scale Modelling as a Characterization Tool to Complete Experimental Data.
Anne Hemeryck 1 , Alain Esteve 1 , Nicolas Richard 3 , Mehdi Djafari Rouhani 1 , Andrew Mayne 2 , Yves Chabal 4 , Gerald Dujardin 2 , Genevieve Comtet 2
1 Laboratoire d’Analyse et d’Architecture des Systèmes, CNRS, Toulouse France, 3 , CEA-DIF, Bruyères-le-Châtel France, 2 Laboratoire de PhotoPhysique Moléculaire, CNRS, Orsay France, 4 Laboratory for Surface Modification, Rutgers University, Piscataway, New Jersey, United States
Show Abstract10:45 AM - U8.3
Nano-scale Imaging with Table-top Extreme Ultraviolet Lasers.
Carmen Menoni 1 , Georgyi Vaschenko 1 , Fernando Brizuela 1 , Courtney Brewer 1 , Yong Wang 1 , Miguel Larotonda 1 , Bradley Luther 1 , Mario Marconi 1 , Jorge Rocca 1 , Weilun Chao 2 , Alexander Liddle 2 , Erik Anderson 2 , David Attwood 2 3 , Alexander Vinogradov 4 , Igor Artioukov 4 , Yuri Pershyn 5 , Victor Kondratenko 5
1 Electrical and Computer Engineering, Colorado State University, Fort Collins, Colorado, United States, 2 Center for X Ray Optics, Lawrence Berkeley National Lab, Berkeley, California, United States, 3 Electrical Engineering and Computer Sciences, University of California Berkeley, Berkeley, California, United States, 4 , P.N. Lebedev Physical Institute, Moscow Russian Federation, 5 , KhPI National Technical University, Kiev Russian Federation
Show Abstract11:00 AM - U8: Optical
BREAK
11:30 AM - **U8.4
What Is The Temperature At The Surface Of A Growing Thin Film?
Gertjan Koster 1
1 GLAM, Stanford University, Stanford, California, United States
Show Abstract12:00 PM - U8.5
Subplantation and Enhanced Oxygen Incorporation During Bias-Assisted Low-Pressure Plasma Deposition of Oxides at the RF-Biased Electrode.
Aram Amassian 1 2 , Patrick Desjardins 2 , Ludvik Martinu 2
1 Materials Science and Engineering, Cornell University, Ithaca, New York, United States, 2 Regroupement québécois sur les matériaux de pointe and Engineering Physics Department, École Polytechnique de Montréal, Montréal, Quebec, Canada
Show AbstractWe report on the sub-surface effects of subplantation in an O2 RF discharge during plasma treatment and thin film deposition at the RF-biased electrode. Using in situ real-time spectroscopic ellipsometry (RTSE), we have obtained time-resolved quantitative information about depth-dependent modifications of c-Si(001) exposed to intense ion bombardment under conditions typically used for oxide deposition. RTSE analysis indicates damage formation within the first second of exposure to a depth of a few nanometers below the surface. Oxide growth is detected immediately thereafter (> 1 to 2 s); it forms near the surface of the target on top of an O deficient interfacial damage layer (DL). Both layers experience a self-limiting growth behavior, as oxide and DL thicknesses reach bias-dependent steady-state values, determined by the maximum ion penetration depth. The results are independently confirmed by performing cross-sectional high resolution transmission electron microscopy (HRTEM) analysis. The in situ experimental study was complemented by Monte-Carlo TRIDYN simulations based on the binary collision approximation, which were modified to calculate dynamic changes in the structure and composition of a target exposed to a broad-energy ion source (RF plasma source and corresponding ion energy distribution function) at high fluence. This novel approach has allowed us to obtain the first quantitatively accurate simulation results of ion bombardment-induced sub-surface oxygen incorporation on time-scales from << 1 s up to a few minutes. We will illustrate the effects of subplantation with the use of practical examples, such as interface broadening in TiO2/SiO2 multilayer optical filters, porosity and interface control in dense-porous Si3N4 multilayer devices, and enhanced oxygen incorporation at the RF-biased electrode in magnetron sputtered ITO coatings.
12:15 PM - U8.6
In Situ Characterization of Gas-Phase Processes During Hafnium Oxide Atomic Layer Deposition.
James Maslar 1 , Wilbur Hurst 1 , Donald Burgess 1 , William Kimes 1 , Nhan Nguyen 1 , Elizabeth Moore 1
1 , NIST, Gaithersburg, Maryland, United States
Show AbstractAs device critical dimensions continue to shrink, atomic layer deposition is increasingly being utilized as a method for depositing the thin (nanometer-scale) conformal layers required for many microelectronics applications, including high κ gate dielectric layers, diffusion barriers, copper seed layers, and DRAM dielectric layers. However, the chemistry of atomic layer deposition processes is still not well understood.In this work, the species present in the gas phase during atomic layer deposition of hafnium oxide were investigated in an attempt to gain insight into the chemistry of this system. Hafnium oxide was deposited on a silicon substrate using tetrakis(ethylmethylamino) hafnium and water. Time-resolved and spatially-resolved in situ Raman and infrared absorption spectroscopic measurements were performed near the growth surface in a research-grade, horizontal-flow reactor under a range of deposition conditions. Density functional theory quantum calculations of vibrational frequencies of expected species were used to facilitate identification of observed spectral features. Three-dimensional, time-resolved computational fluid dynamics simulations of the reactor were performed, including gas phase chemistry, and the results compared to the experimental gas-phase measurements. In addition, spatially-resolved, ex situ spectroscopic ellipsometric measurements were performed on hafnium oxide films and compared to results of in situ gas-phase measurements and computational fluid dynamics simulations.
12:30 PM - U8.7
In situ Defect Spectroscopy: Probing Dangling Bonds During a-Si:H Film Growth by Subgap Absorption.
Richard van de Sanden 1 , Igor Aarts 1 , Andrew Pipino 1 , Erwin Kessels 1
1 Applied Physics, Eindhoven University of Technology, Eindhoven Netherlands
Show Abstract