Oliver A. Williams Cardiff University
Richard B. Jackman University College London
Philippe Bergonzo CEA-LIST
Greg N. Swain Michigan State University
Kian Ping Loh National University Singapore
Monday AM, November 28, 2011
Room 306 (Hynes)
9:30 AM - **N1.1
Recent Progress in Diamond Raman Lasers.
Richard Mildren 1 Show Abstract
1 , MQ Photonics Research Centre, Macquarie University, New South Wales, Australia
Diamond’s relatively low mass elemental mass, strong bonding and highly symmetric lattice provide a host of attractive and outstanding properties including large Raman scattering cross-section, high thermal conductivity, wide transparency range and lattice stability to name a few. Interest in exploiting these properties for optical devices has increased recently in parallel with improvements in the quality of synthetic material grown by chemical vapor deposition. Diamond lasers, which use the phenomenon of stimulated Raman scattering to provide optical gain, is one area in the emergent fields of diamond photonics and optical engineering that has excellent prospects for addressing important challenges in laser source development. In this paper, the recent progress in diamond Raman lasers others will be reviewed. The talk will highlight areas in which diamond holds promise for enhancing laser performance beyond that easily achieved by other means and for addressing important applications.
10:00 AM - **N1.2
Surface Engineering of Graphene.
Andrew Wee 1 , Wei Chen 2 1 Show Abstract
1 Physics, National University of Singapore, Singapore, 0, Singapore, 2 Chemistry, National University of Singapore, Singapore Singapore
A major challenge in graphene-based devices is opening the energy band gap and doping. Molecular functionalization of graphene is one approach to modifying its electronic properties. Surface transfer doping by surface modification with appropriate molecular donors or acceptors represents a simple and effective method to non-destructively dope graphene. Surface transfer doping relies on charge separation at interfaces, and represents a valuable tool for the controlled and non-destructive doping of 2D materials, since traditional dopant implantation methods are not suitable. Molecular self-assembly of bimolecular systems on graphene is demonstrated, and represents a controlled method of surface engineering the properties of graphene. The doping of epitaxial graphene using oxide thin films is also presented. The hole doping effect of graphene modified by MoO3 thin film is confirmed by electrical transport measurements on prototype graphene devices.
10:30 AM - **N1.3
Charge State Manipulation of Single Qubits in Diamond.
Moritz Hauf 1 , Bernhard Grotz 2 , Boris Naydenov 2 , Markus Dankerl 1 , Sebastien Pezzagna 3 , Jan Meijer 3 , Fedor Jelezko 4 , Jörg Wrachtrup 2 , Martin Stutzmann 1 , Friedemann Reinhard 2 , Jose Garrido 1 Show Abstract
1 Walter Schottky Institut, Technische Universität München, Garching Germany, 2 Third Institute of Physics, Stuttgart University, Stuttgart Germany, 3 RUBION, Ruhr-Universität Bochum, Bochum Germany, 4 Institute of Quantum Optics, Ulm University, Ulm Germany
Nitrogen-vacancy defects (NV) in the diamond lattice have been extensively studied in the past for several reasons. NV centers can act as single photon emitters in the visible range with absolute photo-stability. They have found applications in novel fields like quantum computation  and single spin magnetometry. In this context, it is of great interest to understand the effect of diamond surface termination and gain control over the charge state of NV centers in diamond.In ensemble experiments with shallow implanted defects we have shown that by changing the diamond surface termination from oxygen to hydrogen, the fluorescence of the negatively charged NV (NV-) can be suppressed. This effect depends on the implantation energy and dose used for the creation of NV-centers in diamond by low-energy nitrogen implantation . We attribute this behavior to the band bending which occurs at hydrogen-terminated diamond surfaces according to the transfer-doping model. A two-dimensional hole gas is formed at the diamond surface, converting the NV- to either neutral (NV0) or even positively charged NV-centers (NV+). Recently, we have shown that electrostatic control of the charge state of single NV centers can be achieved by using H-terminated surface-conductive diamond devices and an electrolyte gate electrode. Similar to diamond solution-gated field effect transistors , the electrolytic gate electrode provides a precise control over the Fermi level position at the diamond surface. In areas of high nitrogen implantation density, this allows a reversible switching of NV centers from NV- to NV0, whereas in areas of low implantation density single centers could be switched from NV0 into a state which shows now fluorescence, most likely NV+. We have performed self-consistent numerical simulations which can reproduce the surface band bending and the concurrent disappearance of the NV--fluorescence for hydrogen-terminated diamond surfaces in contact with an electrolyte. Furthermore, we can simulate the control of the charge state with an external electrolytic gate for the charge transfer levels NV0/- as well as NV+/0.P. Neumann et al., Nat. Phys. 6, 249 (2010)M.V. Hauf et al., Phys. Rev. B 83, 081304 (2011)M. Dankerl et al., Phys. Rev. Lett. 106, 196103 (2011)
N2: Nitrogen Vacancy Centres in Diamond
Monday AM, November 28, 2011
Room 306 (Hynes)
11:30 AM - **N2.1
Diamond Nanophotonics and Quantum Optics.
Marko Loncar 1 , Tom Babinec 1 , Birgit Hausmann 1 , Jennifer Choy 1 , Irfan Bulu 1 , Yinan Zhang 1 , Qimin Quan 1 Show Abstract
1 School of Engineering and Applied Science, Harvard University, Cambridge, Massachusetts, United States
Individual color centers in diamond have recently emerged as a promising solid-state platform for quantum communication and quantum information processing systems, as well as sensitive nanoscale magnetometry with optical read-out. Performance of these systems can be significantly improved by engineering optical properties of color centers using nanophotonic approaches. In this work we describe a high-flux, room temperature, source of single photons based on an individual Nitrogen-Vacancy (NV) center embedded in a top-down nanofabricated, single crystal diamond nanowires1, 2, plasmonic nano-apertures3, and diamond-based optical cavities4 and waveguides. Using the nanowire geometry, for example, an order of magnitude brighter single photon source is realized, with an order of magnitude lower pump power, compared to an NV center in a bulk diamond1. By embedding diamond nanowires in metals3, it is possible to further increase photon flux by increasing photon production rate via Purcell effect. To that end, we demonstrated Purcell factors of ~6 in geometry that consists of diamond nanoposts embedded in silver. Finally, recently we demonstrated optical nanocavities and waveguides fabricated directly in thin diamond films5. Single-photon emission of NV centers embedded in diamond ring resonators, featuring quality factors on the order of 10,000, has been demonstrated. These devices could enable strong coupling between photons and NV centers. 1.T.M. Babinec, B.M. Hausmann, M. Khan, Y. Zhang, J. Maze, P.R. Hemmer, M. Lončar, Nature Nanotechnology, 5, 195 (2010) 2.B.J.M. Hausmann*, T.M. Babinec*, J.T. Choy*, J.S. Hodges, S. Hong, I. Bulu, A. Yacoby, M.D. Lukin, M. Lončar, New Journal of Physics, 13, 045004 (2011)3.I. Bulu, T.M. Babinec, B.M. Hausmann, J.T. Choy, M. Lončar, Optics Express, 19, 5268-5276 (2011)4.B. J. Hausmann, J. Choy, T. Babinec, Q. Quan, M. McCutcheon, P. Maletinsky, A. Yacoby, M. Loncar, CLEO/QuELS 2011, Baltimore, MD May 5, 2011
12:00 PM - N2.2
Electrical Tuning of Single Nitrogen Vacancy Center States Enhanced by Photoinduced Fields.
F. Joseph Heremans 1 , Lee Bassett 1 , Christopher Yale 1 , Bob Buckley 1 , David Awschalom 1 Show Abstract
1 Center for Spintronics and Quantum Computation, University of California, Santa Barbara, Santa Barbara, California, United States
The nitrogen-vacancy (NV) center in diamond is an excellent qubit candidate due to its long spin coherence, optical addressability, and fast manipulation rates, along with the engineering flexibility of solid-state devices. Furthermore, the coherent coupling of the electronic spin of a single NV center to light  provides a pathway towards integrating NV centers into photonic networks as well as for on-demand generation of spin-photon entanglement. Such applications require the ability to tune the NV-center optical transitions to compensate for the natural variations in local strain caused by sample inhomogeneities that perturbs the electronic orbital states. Here we demonstrate a method to electrically tune individual NV-center orbital Hamiltonians into specific regimes via the DC Stark effect by applying voltages to lithographic gates . The DC Stark shifts reveal a significantly enhanced electric field due to the photoionization of deep charge traps within the diamond. These reproducible fields are predominantly directed perpendicular to the diamond surface allowing for three-dimensional control of the local electric field vector with surface gates only. By harnessing this effect, we are able to tune the excited-state orbitals of individual NV centers to degeneracy, a requirement for several spin-photon entanglement schemes. We also demonstrate the ability to tune multiple NV centers to the same degenerate transition energy. This method should enable the coherent coupling of multiple NV-center spins to indistinguishable photons within a photonic network. B. B. Buckley, G. D. Fuchs, L. C. Bassett, and D. D. Awschalom, Science 330, 1212 (2010). L. C. Bassett, F. J. Heremans, C. G. Yale, B. B. Buckley, and D. D. Awschalom, submitted (2011), arXiv:1104.3878v1 [cond-mat.mes-hall].
12:15 PM - N2.3
In Situ Optimization of NV-Center Creation.
Julian Schwartz 1 , Christoph Weis 1 , Thomas Schenkel 1 Show Abstract
1 , LBNL, Berkeley, California, United States
The NV-defect in diamond has been discussed as an excellent candidate for quantum-information processing at room-temperature. While creating these defect-centers by ion implantation with sufficient spatial resolution to enable entanglement is within reach, the challenge of deterministic creation (conversion efficiency >50%) remains. Increasing the conversion efficiency through co-implantation was studied using different co-implant species and fluences at room temperature and 780 C. Despite the significantly different damage profiles of H, He and C, which were used for the co-implantation, the conversion efficiency did not show a species dependence and displayed similar trends across all combinations of parameters. This strongly indicates the additional effects of charging and possibly defect clustering, by which NV centers are prevented from forming or are trapped into an optically inactive state. We present first experimental results and discuss a strategic approach for investigating this phenomenon.This work was supported by the Laboratory Directed Research and Development Programof the Lawrence Berkeley National Laboratory under US Department of Energy contract no.DE-AC02-05CH11231 and through the DARPA Quest program.References J Schwartz, P Michaelides, C D Weis and T Schenkel, New J. Phys.13, 035022 (2011)
12:30 PM - N2.4
The NV Color Center Qubit in Diamond as Readout for Molecular Qubits.
Wolfgang Harneit 1 2 , Rolf-Simon Schoenfeld 2 , Markus Nimmrich 1 , Angelika Kuehnle 1 Show Abstract
1 Institut fuer Physikalische Chemie, Johannes Gutenberg-Univeritaet Mainz, Mainz Germany, 2 Institut fuer Experimentalphysik, Freie Universitaet Berlin, Berlin Germany
The nitrogen-vacancy (NV) color center is a promising candidate for quantum information processing. Individual NV spins are very robust objects that can be coherently manipulated at room temperature, and used for fast and precise magnetometry. The only drawback of this solid-state qubit is that it cannot be created deliberately with atomic precision due to the inherent limitations of ion implantation. Molecular spin qubits, like the fullerene-encapsulated nitrogen atom N@C60, can be purified chemically and then placed on a Si surface with atomic resolution. The challenge of this project is to use the difficult diamond surface instead and engineer a coherent coupling between N@C60 and a shallow NV center. This would enable truly scalable quantum information processing.We have already achieved the first atomic resolution-imaging of single-crystalline diamond using non-contact AFM . Using nanodiamonds (<50 nm diameter) as a model source for shallow NV centers, we demonstrated that even these slightly less advantageous qubits can be used at room-temperature in a quantum algorithm  and for magnetometry . First steps to engineering the desired coupling will also be reported.References: M. Nimmrich et al., Phys. Rev.B 106 (2010) 040504.  F. Shi, W. Harneit et al., Phys. Rev. Lett. 105 (2010) 040504. R.S. Schoenfeld and W. Harneit, Phys. Rev. Lett. 106 (2011) 030802.
12:45 PM - N2.5
A Diamond Quantum Router of Single Photons at Room Temperature.
Birgit Hausmann 1 , Brendan Shields 2 , Qimin Quan 1 , Jennifer Choy 1 , Murray McCutcheon 1 , Patrick Maletinsky 2 , Tom Babinec 1 , Yiwen Chu 2 , Alexander Kubanek 2 , Amir Yacoby 2 , Mikhail Lukin 2 , Marko Loncar 1 Show Abstract
1 SEAS, Harvard University, Cambridge, Massachusetts, United States, 2 Physics Department, Harvard University, Cambridge, Massachusetts, United States
We present an all-diamond photonic platform on chip for single photon routing as well as broadband optical characterization. An all-diamond photonic network on chip requires coupling of a quantum emitter to a low-loss optical cavity that is efficiently coupled to a routing element such as a waveguide while offering scalability to obtain multi-coupling between resonators and routing elements preferably at room temperature for practical applications. Here, we combine room temperature operation with efficient routing of single photons from a Nitrogen-Vacancy (NV) defect center  that are emitted into the tightly confined mode of a high-finesse ring resonator and evanescently coupled to a waveguide . The single photon flux is extracted efficiently via gratings. Our approach offers versatile scalability of elements. Room temperature routing of single photon flux opens up scenarios for photon entanglement created on chip and extracted in free space which opens up a new route towards quantum key distribution and perfectly secure quantum cryptography.We also present measurements demonstrating broadband operation of single diamond ring resonators on quartz substrate in a transmission tapered fiber set-up in the telecom regime as well as in a scanning confocal microscope in the VIS. Quality factors as high as 12000 were measured .
N3: Doping and Devices
Monday PM, November 28, 2011
Room 306 (Hynes)
3:00 PM - **N3.1
Delta-Doped Diamond Transistor Design.
Etienne Gheeraert 1 Show Abstract
1 Institut Néel, CNRS and University Joseph Fourier, Grenoble France
Diamond is a very attractive material for high power and high frequency electronic applications because of its exceptional physical properties. But diamond devices face one specific difficulty: at room temperature, because of the high ionisation energy of dopants, 0.38 eV for boron and 0.6 eV for phosphorus, free carrier density is very low at room temperature, and resistivity is consequently very high. Ionization energy can be reduced with an increase in the doping concentration, down to zero at the metal-insulator transition, but it also induces a detrimental decrease in the carrier mobility. The solution, proposed initially for silicon in the 80’s and then for diamond, is to fabricate a very thin heavily delta-doped layer in sandwich between two high purity diamond epilayers. The quantum confinement in this thin layer induces a delocalization of the free carriers out of the doped region, allowing holes to move into a high mobility diamond. If the doping level is high enough to reach the metal-insulator transition, ie 4e20 cm-3, then a high hole concentration is expected, even at room temperature. The first critical point is to get a quantum confinement strong enough to delocalize a significant part of the free carriers out of the delta layer. The second point is the ability to modulate the hole concentration with a top gate to build a field effect transistor.In order to get quantitative values regarding these two critical points, we simulated the delta structure solving the Schrödinger and Poisson equations consistently. From the quantum confinement of the hole wavefunctions and their occupancy ratio, the part of holes moving out of the delta layer was deduced, depending on the doping level and delta layer thickness. Then, the field effect control of the hole concentration was addressed. In particular, results show that the diamond breakdown field, even very high, limits the sheet carrier density in the structure, otherwise the field is not strong enough to deplete the channel and close the transistor. Detailed behaviour of the delta structure will be presented, and the transistor properties depending on device structure will be discussed.
3:30 PM - N3.2
Dopant Uniformity in Boron Doped Single Crystal Diamond Films.
Shannon Demlow 1 , Dzung Tran 1 , Nutthamon Suwanmonkha 1 , Isil Berkun 1 , Michael Becker 2 , Timothy Hogan 1 , Timothy Grotjohn 1 2 Show Abstract
1 Department of Electrical and Computer Engineering , Michigan State University, East Lansing, Michigan, United States, 2 , Fraunhofer USA Center for Coatings and Laser Applications, East Lansing, Michigan, United States
Due to its superlative properties, such as a wide bandgap, high breakdown voltage, and high electron and hole mobilities, diamond is a potentially exceptional semiconductor for electronic applications, especially high-temperature and high-power devices. Doping issues continue to be a limitation in this field, and the realization of useful electronic devices requires high quality films with controlled and uniform dopant levels. Precision doping is of increasing concern, as delta, or nm scale, doping, has become an increasingly active area of research for enabling active diamond devices. In our previous work on characterization of boron-doped single crystal diamond (SCD), we have used temperature-dependent conductivity measurements to fit the activation energy, and investigated feedgas chemistries containing carbon dioxide for the control of doping for boron incorporation levels less than 1017 cm-3 [1,2]. We have also compared infrared absorption techniques and SIMS measurements for the determination of incorporated boron, and have shown that infrared absorption spectroscopy is sensitive to surface defects on grown samples .This work expands upon our previous effort to grow and characterize high-quality diamond for electrical applications. Films are deposited on high pressure high temperature SCD substrates in a microwave plasma-assisted CVD reactor with feedgas mixtures including hydrogen, methane, diborane, and carbon dioxide. The effect of carbon dioxide in the feedgas mixture on the incorporated boron is further investigated, and results showing the resulting decrease in electrically active boron are presented. We investigated the dopant spatial variation and the role of defect formation on boron incorporation, using infrared and Raman spectroscopy, conductivity and Hall effect measurements, secondary ion mass spectroscopy (SIMS) and scanning electron microscopy (SEM). We present the results of our investigation of the spatial uniformity of the dopant profile in boron doped diamond both across the growth surface and versus depth into the film, as well the properties of the boron doped layers as a function of temperature. Results for boron concentration levels ranging from below 1017 cm-3 to approximately 1020 cm-3 are reported. References S.N. Demlow, M. Becker, and T. Grotjohn, Electrical Conduction Properties of Single Crystal, Boron-Doped Diamond Films, New Diamond and Nano Carbon Confernce (2011).  S.N. Demlow, T.A. Grotjohn, T. Hogan, M. Becker and J. Asmussen, Determination of Boron Concentration in Doped Diamond Films, MRS Proceedings (2011) 1282, mrsf10-1282-a05-15 doi:10.1557/opl.2011.444
3:45 PM - N3.3
Sharp Doped Delta Interfaces by Tuning the Species Residence Time.
Pierre-Nicolas Volpe 1 , Nicolas Tranchant 1 , Jean - Charles Arnault 1 , Christine Mer 1 , Samuel Saada 1 , François Jomard 2 , Philippe Bergonzo 1 Show Abstract
1 , CEA - LIST, Gif sur Yvette France, 2 , GeMaC - CNRS, Meudon France
Delta doping of diamond is seen as a very promising route to fabricate novel generation power and electronic devices [1,2]. Nevertheless, the achievement of abrupt interfaces requires low residence time for involved species.We report on the growth optimisation of diamond boron doped single crystals in a MPCVD reactor where the gas injection has been especially designed to reduce the residence time of species in the substrate vicinity. This technique was applied to rising and descending boron profiles. Reflectometry and SIMS results will be shown with very promising profiles from 2*10^21 to 2*10^16 at/cm3 displaying doping gradients close to 3 nm/decade.  PN.Volpe, P.Muret, J.Pernot, F.Omnès, T.Teraji, F.Jomard, D. Planson, P.Brosselard, N.Dheilly, B.Vergne, S.Scharnholtz. Applied Physic Letters, 97, 22, 223501 (2010). P. Muret, P.N. Volpe, T.-N. Tran-Thi, J. Pernot, C. Hoarau, F. Omnès, T. TerajiDiamond and Related Materials, 20, Issue 3, 285-289 (2011).
N4: Diamond Nanoparticles: Properties and Applications
Monday PM, November 28, 2011
Room 306 (Hynes)
4:30 PM - **N4.1
Odour Monitoring Using Nanodiamond Based Gravimetric Sensor Arrays and Multiparametric Learning for Security Applications.
Emmanuel Scorsone 1 , Benoit Tard 1 , Philippe Bergonzo 1 Show Abstract
1 , CEA-LIST, Gif-sur-Yvette France
Generally speaking gravimetric gas sensors are made of a mass sensitive transducer, such as a micro-cantilever, quartz crystal microbalance or surface acoustic wave (SAW) device coated with a sensitive layer designed to have a high affinity with target molecules. The transducers are resonant devices which exhibit a shift in the resonant frequency upon mass loading when the gas molecules interact with the coating. High sensitivity is achieved both by the transducer and the coating whereas selectivity is mostly achieved by the coating. The design of highly specific sensors is only possible using coatings made of highly specific receptors. Unfortunately 100 % specific receptors or close only exist in biology and include antibodies, enzymes, DNA, etc. These receptors are generally not optimum for operation in the gas phase and their fairly short lifetime limits their use for field applications. Hence non biological receptors would be preferred, but unfortunately no such material has been shown to be 100 % specific to any volatile compound to date. Also the use of highly specific single sensors is not adequate for odor measurement which generally requires the detection of complex gas mixtures. An alternative approach consists of using a multisensor array. In this array, each sensor is coated with a different selective layer having each a broad selectivity to chemical compounds or families of compounds. The relative response signal of the sensors recorded simultaneously gives a fingerprint of a single gas or gas mixture. Combining this approach with data training and pattern recognition tools enables the discrimination of odors even though each individual sensor is not selective. The sensors used in this approach often take advantage of the availability of a wide range of polymers coatings but those feature a number of critical issues such as premature aging, poisoning, lack of reproducibility, etc. In the recent year we have developed alternative coatings made of functionalized nanodiamond. These are coated in particular onto highly sensitive 433 MHz SAW enabling the detection of hazardous volatile compounds in the low ppb range. The small size of the diamond nanoparticles enables high control of coating thickness hence a high level of reproducibility and high sensitivity due to high surface area. Moreover the sp3 nature of the grains offer a robust platform onto which can be immobilized a wide variety of receptors using the carbon chemistry via chemical or plasma routes that will be exposed. The diamond sensor arrays have allowed the selective detection of DMMP, a stimulant for sarin gas, as well as explosive vapors (EGDN, dynamite, etc.) for instance when hidden in a luggage. An insight toward the next generation diamond sensor arrays functionalized with highly stable odorant binding proteins will also be discussed.
5:00 PM - N4.2
Electrostatic Self-Assembly of Diamond Nanoparticles.
Oliver Williams 1 2 , Jakob Hees 2 , Armin Kriele 2 Show Abstract
1 School of Physics & Astronomy, Cardiff University, Cardiff United Kingdom, 2 Micro and Nano Sensors, Fraunhofer IAF, Freiburg, BW, Germany
Diamond nanoparticles are exciting candidates for a diverse array of applications from single photon sources, through drug delivery and bio-labelling to the nucleation sites for growth of nanocrystalline diamond films. The apparent lack of toxicity, facile functionalisation strategies and stability makes them ideal bio-markers and drug delivery agents. The high quantum yield, photostability and fluorescence in the visible range are highly desirable optical properties for both bio-labelling and solid-state single photon sources.For both biological solution based colloids and solid-state substrate supported nanoparticle systems, the diamond nanoparticles must be individually accessible and treatable en masse. In both cases the nanoparticles are initially manipulated in colloidal dispersions and thus the nature of diamond nanoparticles in solution is critical. Unfortunately, diamond nanoparticles produced by the detonation process are tightly bound in aggregates that are difficult to separate into mono-disperse particle colloids. The aggregate size can be up to 100 nm in solution, far in excess of the 5 nm core particle sizes, rendering the dispersions inadequate for the majority of the aforementioned applications.Recently it has been shown that prior treatment of the particles by high temperature annealing in hydrogen gas or air can yield mono-disperse colloids of diamond nanoparticles. Although these approaches solve the colloidal dispersion issue, there is little information on the assembly of these nanoparticles at solid–liquid interfaces. This is a critical step for the production of high nucleation densities of diamond nanoparticles for the nucleation of nanocrystalline diamond films and reducing the nucleation density for discrete single photon emitters supported on quartz or other substrates. In this work we explain the mechanism behind the self-assembly of diamond nanoparticles onto silicon dioxide surfaces. Silicon dioxide is chosen due to it being the natural oxide of all silicon wafers and thus omnipresent in silicon supported diamond nanoparticle systems. It is also the most used transparent substrate for supported diamond nanoparticle single photon emitters. Characterisation of the zeta potential of both the diamond and silicon dioxide shows a clear pH window of electrostatic attraction, outside of which the system is unstable. By controlling the surface groups of the diamond nanoparticles and the pH of the solution, it is possible to yield either very high nucleation densities ideal for diamond growth (~1012cm-2) or low nucleation densities (<109cm-2) ideal for discrete single photon sources.
5:15 PM - N4.3
Detonation Nanodiamons: Properties and Selected Applications.
Robert Edgington 1 , Richard Jackman 1 Show Abstract
1 London Centre for Nanotechnology, University College London, London United Kingdom
Nanodiamonds (NDs), synthesized by a detonation process  are typically formed of 5nm core crystals tightly aggregated to sub-micron particles. Recent advances in the methods for treating these particles have enabled solutions of disaggregated NDs to be prepared , from which is it possible to coat 3D objects with NDs using simple room temperature sonication methods. In contrast, the deposition of thin film diamond using plasma-enhanced chemical vapour deposition (CVD) requires elevated temperatures (~8500C) ruling out many substrate materials, and complex plasma engineering for 3D coating. Hence, there is considerable interest in exploring the properties of NDs, and contrasting them to thin film diamond, and in applications for ND coatings on a wide range of substrates. In this paper, methods for producing and processing NDs will be reviewed, and the electrical properties of both aggregated  and monodispersed  forms of NDs considered. Interestingly, both forms of ND show properties remarkable similar to thin film diamond, in terms of their dielectric properties. Different forms of surface functionilisation of NDs, and the methods for producing them will be discussed. Diamond-based ISFETs have previously been demonstrated to be effective sensors, when the p-type conductive channel if formed by so-called ‘surface-transfer doping’ involved hydrogenation of the diamond surface. However, this form of device suffers from instability due to the need for an adsorbate layer to activate the doping process. We have recently shown that an ND coating on the gate region of such an ISFET obviates the need for such an adsorbate layer, leading to more stable ISFET operation . We have recently reported upon the suitability of nanodiamond monolayers to act as a platform for neuronal cell growth . Neurons cultured on various ND-coated substrates perform remarkably well, without the need for the standard protein-coated materials normally required for their initial cell attachment. Moreover, sustained neurite outgrowth, cell-autonomous neuronal excitability and excellent functionality of the resulting electrical networks result. Hence, it would appear ND layering provides an excellent growth substrate on various materials for functional neuronal networks and bypasses the necessity of protein coating, which promises great potential for chronic medical implants. Shenderova et al Crit. Rev. Solid State Mater. Sci., 27, 227 (2002) Williams et al Chem. Phys. Letts., 445, 255 (2007)  Bevilacqua et al Appl. Phys. Letts., 93, 132115 (2008)  Chaudhary et al., Appl. Phys. Letts., 96, 242903 (2010)  Ahmad et al Appl. Phys. Letts., 97, 203503 (2010)  Thalhammer et al, Biomaterials 31, 2097 (2010)
5:30 PM - N4.4
Surface Reconstruction and Selective Reoxidation on Annealed Detonation Nanodiamond.
Tristan Petit 1 , Jean-Charles Arnault 1 , Hugues Girard 1 , Mohamed Sennour 2 , Tsai-Yang Kang 3 , Chia-Liang Cheng 3 , Philippe Bergonzo 1 Show Abstract
1 Diamond Sensors Laboratory, CEA-LIST, Gif-sur-Yvette France, 2 Paristech CNRS UMR 7633, Mines Paris, Evry Taiwan, 3 Department of Physics, National Dong Hwa University, Hua-Lien Taiwan
The use of nanodiamond is very attractive for biomedical applications due to their unique surface chemistry and their fluorescent emitting centers like NV centers. The chemical reactivity of the sp3 carbon on the nanodiamond surface terminated with different groups such as carboxyls, hydroxyls or hydrogen is now well controlled and enables various functionalization routes. However it was shown recently that sp2 hybridized carbon on the nanodiamond surface could also lead to outstanding chemical or catalytic reactivities. If it is well-known that nanodiamonds are progressively transformed into Onion-Like Carbon (OLC) by annealing under vacuum at temperature above 1100°C, surface modifications of nanodiamonds occurring at temperatures below 1000°C remain unclear. This temperature range is though particularly interesting because it corresponds to the early stages of surface graphitization without alteration of the diamond core.In this study we investigate the surface modifications on detonation nanodiamonds induced by annealing under vacuum at temperature lower than 1000°C. We demonstrate by XPS, AES and HRTEM analysis that the nanodiamond surface reconstructs into graphitic nanostructures that can be controlled down to a single fullerene-like shell. Furthermore, we observed that after air exposure, the surface was spontaneously and selectively reoxidized. Consequently, the annealed nanodiamond could easily be suspended in water and have a highly positive zeta potential. The role of surface chemistry on the zeta potential change will also be discussed based on XPS, FTIR and DLS characterizations.1. Huang, L.-C.L. and H.-C. Chang. Langmuir, 2004. 20(14): p. 5879--5884.2. Krueger, A., et al. Langmuir, 2008. 24(8): p. 4200--4204.3. Girard, H.A., et al. Physical Chemistry Chemical Physics, 2011. 13(24): p. 11517-11523.4. Meinhardt, T., et al., 2011. 21(3): p. 494-500.5. Zhang, J., et al., Angewandte Chemie, 2010. 49(46): p. 8640-8644.6. Kuznetsov, V.L., et al., Journal of Applied Physics, 1999. 86(2): p. 863-870.
5:45 PM - N4.5
Fluorescent Nanodiamonds as Vector for siRNA Delivery to Ewing Sarcoma Cells.
Anna AlHaddad 2 , Marie-Pierre Adam 1 , Catherine Durieu 3 , Jacques Botsoa 1 , Géraldine Dantelle 4 , Sandrine Perruchas 4 , Thierry Gacoin 4 , Christelle Mansuy 5 , Solange Lavielle 5 , Claude Malvy 2 , Eric Le Cam 3 , Francois Treussart 1 , Jean-Rémi Bertrand 2 Show Abstract
2 Laboratoire de Vectorologie et Théapeutiques Anticancéreuses, CNRS UMR8203, Université Paris Sud 11, Institut de Cancérologie Gustave Roussy, Villejuif France, 1 Laboratoire de Photonique Quantique et Moléculaire, CNRS UMR 8537, Ecole Normale Supérieure de Cachan, Cachan France, 3 Laboratoire de Signalisation, Noyaux et Innovations en cancérologie, CNRS UMR8126, Université Paris Sud 11, Institut de Cancérologie Gustave Roussy, Villejuif France, 4 Laboratoire de Physique de la Matière Condensée, CNRS UMR7643, , Ecole Polytechnique, Palaiseau France, 5 Laboratoire des Biomolécules, CNRS UMR7203, Université Pierre et Marie Curie,, Ecole Normale Supérieure, Paris France
Nanotechnologies are opening new routes to the anti-cancer drug-delivery domain, providing a good tissue distribution and a low toxicity. Drug delivery vehicles relying on nanoparticles have been proposed, among which the one made of diamond (size<20 nm) is a promising candidate .We have investigated the delivery of small interfering RNA (siRNA) by nanodiamonds (ND) into cells in culture, in the context of the treatment of a rare child bone cancer (Ewing sarcoma) by such a gene therapy. siRNA is adsorbed onto the NDs after their coating with cationic polymers, so that the interaction is strong enough for the complex to pass the cell membrane without losing the drug, while not preventing its subsequent release.The cellular studies showed a specific inhibition of the gene expression by the ND-vectorized siRNA, at the mRNA and protein levels. The fluorescence of color center created in the nanodiamonds was used to monitor the release in the intracellular medium of fluorescently-labeled siRNA. This technique brings a quantitative insight in the efficiency of siRNA to stop cell proliferation .We also investigated in details the internalization process and the intracellular release of siRNA by the cationic NDs, using a combination of Transmission Electron Microscopy analysis, fluorescence microscopy and chromatography techniques. Different behaviors were observed depending on the type of cationic polymer, offering a tool for a better control of the delivery process.References E.K. Chow et al., Sci Transl Med 3, 73ra21 (2011) A. AlHaddad et al., submitted, arXiv:1106.2252v1 [q-bio.BM]
Oliver A. Williams Cardiff University
Richard B. Jackman University College London
Philippe Bergonzo CEA-LIST
Greg N. Swain Michigan State University
Kian Ping Loh National University Singapore
N5: Electron Emission
Tuesday AM, November 29, 2011
Room 306 (Hynes)
9:30 AM - N5.1
Secondary Electron Emission from Hydrogenated Nanocrystalline Surfaces: A Temporal Study.
Joseph Welch 1 , Aysha Chaudhary 1 , Richard Jackman 1 Show Abstract
1 London Centre for Nanotechnology, University College London, London United Kingdom
Secondary electron emission from diamond surfaces which display negative electron affinity (NEA) can be used for the purposes of electron amplification. There are two approaches currently under investigation for the formation of stable NEA diamond surfaces. The first involves the addition of a monolayer of an alkali metal, such as Cs or Li, to the diamond surface. A simpler method involves hydrogenating the diamond surface. When sample surface is hydrogenated, the electron affinity drops so the diamond surface becomes NEA, which assists in the emission of the secondary electrons. Before any NEA is revealed any wetting layer, must be removed, since water adds on an extra layer of OH2 molecules, which constitutes a second capacitor. This capacitor is in series with the first capacitor of C-H, thereby increasing the surface electron affinity to positive (PEA). However, When primary electrons impinge onto the hydrogenated sample surface, the hydrogen desorbs over time, which in turn reduces NEA as the vacuum-barrier height becomes too high for the secondary electrons to escape.In this paper the temporal evolution of the secondary emission yield (SEY), or electron gain, is explored at different temperatues. Gains greater than 10 can be readily recorded, and it can be shown that the surface can be made sufficiently stable for some types of electron amplification applications, where low currents are used.
9:45 AM - N5.2
Diamond: Photocathode and Electron Amplifier.
John Smedley 1 , Ilan Ben-Zvi 1 , Xiangyun Chang 1 , Jonahan Rameau 1 , Triveni Rao 1 , Erdong Wang 1 , Qiong Wu 1 , Erik Muller 2 , Tianmu Xin 2 Show Abstract
1 , Brookhaven National Laboratory, Upton, New York, United States, 2 Physics and Astronomy, Stony Brook University, Upton, New York, United States
Due to its ability to form a stable negative electron affinity (NEA) surface, diamond can operate as both an electron amplifier and as a photocathode. It has the potential to dramatically increase the average current available from photoinjectors, perhaps to the ampere-class performance necessary for flux-competitive fourth-generation light sources. We report on electron emission from hydrogen-terminated diamond, with both photon and electron generated carriers. An emission gain of over 200 has been achieved using a thermionic cathode; electron emission has also been observed with photon-generated carriers. The emission mechanism from H-terminated diamond has been investigated using Angle-Resolved Photoemission Spectroscopy, with both laser (6 eV) and synchrotron (12-20 eV) illumination. A novel emission mechanism relying on optical phonons to connect the conduction band minimum to the gamma point, allowing normal emission of electrons, has been identified. The implications of this mechanism on the function of the amplifier as an electron source will be discussed.
10:00 AM - N5.3
Ultraviolet Photodetector Driven by Diamond Cold Cathode.
Tomoaki Masuzawa 1 , Richika Kato 1 , Masanori Onishi 1 , Yuki Kudo 2 , Ichitaro Saito 3 , Takatoshi Yamada 4 , Ken Okano 1 Show Abstract
1 Dept. of Physics, ICU, Tokyo Japan, 2 Graduate School of Pure and Applied Science, University of Tsukuba, Tsukuba Japan, 3 Dept. of Engineering, University of Cambridge, Cambridge United Kingdom, 4 Nanotube research center, National Institute of Advanced Industrial Science and Technology, Tsukuba Japan
Recent advances in optical engineering opened up various applications using ultraviolet (UV) light. These applications include a new generation optical storage device, UV photolithography, and medical diagnosis such as positron emission tomography (PET). For integrated devices, a common choice for a low-cost UV detector is a silicon (Si) avalanche photodiode (APD), though the relatively narrow band gap of Si tends to result in a high dark current. For such applications, solid-state APDs are intensively studied using wide-gap semiconductors, such as silicon carbide and various nitride materials . In medical diagnosis, however, detection of weak UV light is becoming more important, and a demand in high sensitive photodetectors is much greater than that in fabrication cost or device size. In such field, photo multiplier tubes are still commonly used for their high gain (~1,000,000) and low dark current, even though they require high operation voltage of ~1kV and have slow response due to signal multiplication process. In order to develop a high-gain UV detector with low operation voltage and short response time, we propose a photodetector that consists of a diamond cold cathode and selenium-based photoconductive film.In our previous studies, we were focusing on fabrication of a photodetector, which is one of the practical applications of cold cathode, by combining a diamond cold cathode and an amorphous selenium (a-Se) photoconductor. The prototype photodetector showed a low operation voltage, and could detect visible lights of ~0.5 lx .In this study, an attempt was made to detect UV light using the prototype photodetector. Field emission characteristics of the detector are compared between under UV illumination versus no illumination. The result suggested an increase in the emission current with a fixed operating voltage, by the UV light illumination. This indicated that the fabricated prototype photodetector could detect UV light. Although the detection efficiency is not high compared to solid-state avalanche photodiodes in previous studies, drastic improvement in the detection gain is expected when the device is operated in the avalanche multiplication mode. X. Xin et al., IEEE Electronics Letters 41 (2005) 212. J. B. Limb et al., Appl. Phys. Lett 89 (2006) 011112. N. Kato et al., J. Vac. Sci. Technol. B 24 (2006) 1035.
10:15 AM - **N5.4
Nanostructure TEM Analysis of Diamond Cold Cathode Field Emitters.
Travis Wade 3 , Nikkon Ghosh 1 , James Wittig 1 3 , Weng Kang 1 , Larry Allard 4 , Kinga Unocic 4 , Jim Davidson 1 3 , Norman Tolk 2 3 Show Abstract
3 Material Science & Eng, Vanderbilt University, Nashville, Tennessee, United States, 1 Electrical Engineering, Vanderbilt University, Nashville, Tennessee, United States, 4 , Oak Ridge National Labs, Oak Ridge, Tennessee, United States, 2 Physics, Vanderbilt University, Nashville, Tennessee, United States
Chemical vapor deposited (CVD) diamond is an attractive material for electron field emitters, in part because of its low or negative electron affinity, mechanical strength, and chemical inertness. CVD nanodiamond possesses unique properties including controlled sp2-carbon content and p-type electrical conductivity when doped with boron. Arrays of ultra-sharp diamond tips with a radius of curvature less than 5 nm have been fabricated and show significant improvement in emission brightness and turn-on field compared to other field emitters. Variation in field-dependent emission thresholds is considered to arise from variation in the geometric field enhancement factor of individual tips, followed by the additional emission of more tips as the field increases. However, above 5V/µm, all participating tips are observed to be active and electron emission behavior is consistent with the Fowler-Nordheim electron tunneling description. Irregularities in emission behavior between tips were historically attributed to anomalies in the fabrication process: “sharp” vs. “less sharp” tips. However, differences have been observed in electron emission thresholds between tips that appear to be equally well formed. This study examines the emitter to provide insight into how surface and subsurface structure may affect emission.Sub-surface parameters including dopant concentrations, oriented graphite present at grain boundaries on the diamond surfaces, and structural features such as voids, influence the transport of electrons to the emitter surface. As a principal mode of electron conduction in nanodiamond, the presence and orientation of graphite at the grain boundaries may substantially influence a tip’s electron emission behavior. Transmission electron microscopy performed in this study provides new insight into tip structure and composition with implications for field emission and diamond growth.
N6: Biosensors and Bioelectronics
Tuesday AM, November 29, 2011
Room 306 (Hynes)
11:15 AM - **N6.1
Diamond and Graphene: Advanced Carbon Materials for Bioelectronics.
Jose Garrido 1 Show Abstract
1 Walter Schottky Institut, TU München, Garching Germany
Biosensing and bioelectronic applications have enormously profited from employing field effect transistors as transducing devices, mainly due to their intrinsic amplification capability and the high integration offered by semiconductor technology. Due to the maturity of Si technology, most of the work with the so-called solution-gated field effect transistors (SGFETs) has been done based on Si-MOSFETs. However, several disadvantages of the Si technology, such as high electronic noise and poor stability, have motivated the search for more suitable materials. The sensitivity of SGFETs devices largely depends on the distance between the conductive channel and the surface. Therefore, the use of FETs structures with surface channels offer clear advantages. In this respect, the surface conductive channel of hydrogenated diamond appears as an ideal candidate for the development of highly sensitive SGFETs. Similarly, the surface conduction offered by graphene offers similar, if not better, potential. Furthermore, the facile integration of graphene electronics with flexible substrates might open the way for a true breakthrough in the field of electrically functional neural prosthesesIn this contribution, I will report on our work towards the development of graphene- and diamond-based platforms for applications in biosensing and bioelectronics. The electronic properties of graphene and diamond in contact with aqueous electrolytes will be discussed. It will be shown that the graphene/electrolyte and the diamond/electrolyte interfaces can be exploited for capacitive charging using a gate electrode to control the electrolyte potential, thus enabling the preparation of SGFETs. Graphene and diamond SGFETs will be compared to Si-SGFETs based on the gate sensitivity and low-frequency noise performance of these devices. Both diamond and graphene SGFETs will be shown to exhibit a high transconductance and correspondingly high sensitivity, together with an effective gate noise as low as tens of µV. Different cell types have been cultured onto graphene and diamond surfaces in order to assess the biocompatibility of these materials for those particular cell cultures. It was found that cells show a healthy growth comparable to standard glass substrates. Furthermore, we have investigated the ability of diamond and graphene SGFETs to transduce the electrical activity of electrogenic cells. To this end, cardiomyocyte-like HL-1 cells have been cultured on SGFET arrays. Employing the transistors beneath, we were able to detect and resolve the action potentials generated by the HL-1 cells. The propagation of the cell signals across the transistor array can be successfully tracked. These results demonstrate the potential of diamond and graphene to outperform state-of-the-art Si-based devices for biosensor and bioelectronic applications.
11:45 AM - N6.2
A Fully Ion Beam Micromachined Diamond Biosensor Designed for the Detection of Quantal Catecholamine Secretion from Chromaffin Cellschromaffin Cells.
Ettore Vittone 1 , Valentina Carabelli 2 , Emilio Carbone 2 , Sara Gosso 2 , Leonardo La Torre 3 , Paolo Olivero 1 , Federico Picollo 1 , Valentino Rigato 3 Show Abstract
1 Expeirmental Physics Dept. and NIS excellence center, University of Torino, Torino Italy, 2 Department of Neuroscience, NIS Centre of Excellence , University of Torino, Torino Italy, 3 INFN- National Laboratories of Legnaro, University of Torino, Legnaro (Pd) Italy
It is shown that ion beam direct writing of graphitic channels in monocrystalline diamond is an effective tool to fabricate sensors for biochemical analysis.A Ib monocrystalline diamond sample (3x3x0,5 mm3) was irradiated with a focused 1.6 MeV He ion beam scanned over a segmented path in order to define highly damaged regions with a resolution of the order of micrometer. A suitable variable thickness mask was used onto the diamond surface to modulate the penetration depth of ions and to shrink the damage profile toward the surface. After the irradiation, the sample was annealed at high temperature (> 800°C) to promote the conversion to the graphitic phase of the end-of range (about 3 micrometer in depth) regions which experienced an ion induced damage exceeding a damage threshold of the order of 1E23 vacancies/cm3 and to recover the sub-threshold damaged regions to the highly resistive diamond phase. This process provided buried highly conductive graphitic channels embedded in a highly electrically insulating and chemically inert diamond matrix, with end points (with dimension below 10 micrometer) emerging to the surface and available to be used as electrodes.The channels show a graphitic-like conductivity (around mOhmxcm); from amperometric characterization, the dark current recorded when one of the terminals was immersed in distilled water or in tyrode saline solution, was below 10 pA for a bias voltage of 800 mV with respect to a reference Ag/ClAg electrode.The microelectrodes show a high electrochemical responsiveness to oxidizable molecules as evaluated by recording the drift redox currents following the addition of consecutive micro-drops of adrenaline in proximity to the emerging channels.Finally, the functionality of these channels for the detection of bio-signals will be also tested by positioning adrenal chromaffin cells in the proximity of the emerging channels and recording the amperometric signals corresponding to the quantal release of catecholamines contained in a single secretory vesicle.
12:00 PM - N6.3
Electron Transfer between Diamond Electrodes and Biomolecules Immobilized via Conductive Polymer Brushes.
Andreas Reitinger 1 , Naima Hutter 2 , Franz Fuchs 1 , Andreas Donner 1 , Roberta Caterino 1 , Oliver Williams 3 , Martin Stutzmann 1 , Rainer Jordan 4 , Jose Garrido 1 Show Abstract
1 Walter Schottky Institut, Technische Universität München, Garching Germany, 2 Wacker Chair of Macromolecular Chemistry, Technische Universität München, München Germany, 3 , Fraunhofer-Institut für Angewandte Festkörperphysik IAF Freibur, Freiburg Germany, 4 Chair of Macromolecular Chemistry, Technische Universität Dresden, Dresden Germany
The development of diamond-based amperometric biosensors requires a precise control over the biofunctionalization of diamond surfaces . In this work, we report on two routes to immobilize redox-active bio-molecules on or close to the surface of nanocrystalline diamond electrodes.
The first, more conventional, approach is based on a variety of relatively simple and small linker molecules, which in principle allows for a direct electron transfer between the coupled bio-molecules (including cytochrome c, horseradish peroxidise, and glucose oxidase) and the diamond electrode.
In the second approach we use polymer brushes to immobilize bio-molecules. In contrast to the immobilization based on small linker molecules, polymer brushes enable a much higher loading of biomolecules. Using self-initiated photografting and photopolymerization (SIPGP), brushes of polymers with lengths ranging from several nanometers to a few micrometers can be created on the diamond surface . The SIPGP results in a strong covalent bond between polymer and diamond. We further demonstrate that biomolecules can be effectively incorporated into the polymer brushes . However, when bio-molecules are immobilized along these polymers, an efficient electron transfer path between molecules further away from the surface and the diamond electrode has to be established. Here, we use ferrocene groups to mediate electrons along the polymers and compare different ways to integrate the ferrocene molecules into the polymer brushes. Having demonstrated the feasibility of this approach in principle, we will discuss the details of the electron transfer mechanism in these systems.
 A.Härtl et al., Nature Materials 3, 736 (2004)
 N.A. Hutter et al., Phys. Chem. Chem. Phys. 12, 4360 (2010)
 N.A. Hutter et al., Soft Matter 7, 4861 (2011)
12:15 PM - **N6.4
Covalently Functionalizing Graphene FETs for Real-Time Biosensing.
Paul Sheehan 1 Show Abstract
1 U.S. Naval Research Laboratory, U.S. Naval Research Laboratory, Washington, District of Columbia, United States
The sensitive and specific detection of biomolecules without using a label is a long-standing goal of the biosensors community. Several promising advances of the past several years formed biological field effect transistors (bioFETs) that have as the gate nanoscale materials such as nanowires and carbon nanotubes. The nanoscale dimensions of these materials allow the small charges associated with biomolecules to significantly change conduction through the gate. These conduction changes can be correlated with solution concentration to give precise readouts. While bioFETs are a promising way forward, there are many processing difficulties associated with these 1-D materials that inhibit large scale, reproducible fabrication of devices. Here, we will discuss our efforts to develop biosensors based on 2-D chemically modified graphene. These devices impart the sensitivity gains seen from other nanoscale materials, but offer a configuration that is amenable to processing techniques that are common in the semiconductor industry. We will focus primarily on chemically modifying graphene for attachment of biomolecular probes. Devices utilizing both graphene and graphene oxide will be covered, and surface spectroscopic studies of the material modification will be discussed. Successful results for the detection of specific DNA hybridization will also be presented, with detection limits that compare favorably with the best results reported from nanowire bioFETs.
N7: Diamond Growth
Tuesday PM, November 29, 2011
Room 306 (Hynes)
2:45 PM - **N7.1
Novel Graphene and Nanodiamond Growth Strategies Using Large Area Linear-Antenna Microwave Plasma Enhanced CVD System.
Milos Nesladek 3 , Andy Taylor 1 , Frantisek Fendrych 1 , Otakar Frank 2 , Martin Kalbac 2 , Ladislav Kavan 2 Show Abstract
3 IMO, Hasselt University, IMOMEC division IMEC, Diepenbeek Belgium, 1 Institute of Physics, Academy of Sciences of the Czech Republic, Prague Czechia, 2 Department of Electrochemical Materials, Academy of Sciences of the Czech Republic, Prague Czechia
Graphene growth for large-area electronic and optical applications has recently attracted much interest. Several growth strategies including chemical exfoliation, thermal CVD, plasma CVD and others have been used. Recently it has been suggested that graphene layers can be prepared by low pressure MW systems, such as slit-antenna delivery , at lower temperatures. However, the first results suggested also the presence of amorphous carbon in the atomic monolayers. In this work we study the use of a low pressure linear antenna MW plasma delivery system working in pulsed mode with CH4:H2 and CH4:Ar:H2 gas mixtures for the growth of graphene on Cu foils at Ts 400 - 700°C, subsequently transferring them to glass substrates. We have recently used this system for nanodiamond (ND) thin films growth. Firstly, we discuss the conditions leading to transition from ND to graphene growth. Secondly, we used Raman spectroscopy  to study transition from amorphous layers to graphene by optimising the growth conditions such as plasma parameters, gas composition and substrate temperature. For comparison we use thermal CVD to prepared graphene monolayers. Raman spectroscopy using various laser excitations shows very sharp graphene signatures at 1600 cm-1 and 2660 cm-1, pointing to high quality graphene layers. Additionally we use Photothermal Deflection Spectroscopy (PDS) to monitor optical absorption to follow the transition from amorphous graphene layers, showing the band-gap opening for low temperature layers (400 - 600 °C), to highly crystalline monolayers by changing the substrate temperature and plasma parameters in MW – LA PE CVD system. Kim J, Ishihara M, Koga Y, et al. App. Phys. Lett. 98, 091502, 2011  Taylor A, Fendrych F, Fekete L, et al., Diam. Related Materials 20, p 613-615, 2011.  Kalbac M, Farhat H, Kong J, et al., NanoLetters, 11 , p 1957-1963, 2011
3:15 PM - N7.2
Heteroepitaxial Growth of High Quality Diamond Films on Silicon Carbide.
Gary Harris 1 2 , Robert Westervelt 3 , Halvar Trodahl 3 , James Griffin 1 , Crawford Taylor 1
1 HNF, Howard University, Washington, District of Columbia, United States, 2 Electrical & Computer Engineering, Howard University, Washington, District of Columbia,