Showing papers on "Diamond published in 2009"

Ultralong spin coherence time in isotopically engineered diamond

Abstract: As quantum mechanics ventures into the world of applications and engineering, materials science faces the necessity to design matter to quantum grade purity. For such materials, quantum effects define their physical behaviour and open completely new (quantum) perspectives for applications. Carbon-based materials are particularly good examples, highlighted by the fascinating quantum properties of, for example, nanotubes or graphene. Here, we demonstrate the synthesis and application of ultrapure isotopically controlled single-crystal chemical vapour deposition (CVD) diamond with a remarkably low concentration of paramagnetic impurities. The content of nuclear spins associated with the (13)C isotope was depleted to 0.3% and the concentration of other paramagnetic defects was measured to be <10(13) cm(-3). Being placed in such a spin-free lattice, single electron spins show the longest room-temperature spin dephasing times ever observed in solid-state systems (T2=1.8 ms). This benchmark will potentially allow observation of coherent coupling between spins separated by a few tens of nanometres, making it a versatile material for room-temperature quantum information processing devices. We also show that single electron spins in the same isotopically engineered CVD diamond can be used to detect external magnetic fields with a sensitivity reaching 4 nT Hz(-1/2) and subnanometre spatial resolution.

Ab initio theory of the lattice thermal conductivity in diamond

Abstract: We present a first-principles theoretical approach to calculate the lattice thermal conductivity of diamond based on an exact solution of the Boltzmann transport equation. Density-functional perturbation theory is employed to generate the harmonic and third-order anharmonic interatomic force constants that are required as input. A central feature of this approach is that it provides accurate representations of the interatomic forces and at the same time introduced no adjustable parameters. The calculated lattice thermal conductivities for isotopically enriched and naturally occurring diamond are both in very good agreement with experimental data. The role of the scattering of heat-carrying acoustic phonons by optic branch phonons is also investigated. We show that inclusion of this scattering channel is indispensable in properly describing the thermal conductivity of semiconductors and insulators. The accurate adjustable-parameter-free results obtained herein highlight the promise of this approach in providing predictive descriptions of the lattice thermal conductivity of materials.

Chemical vapour deposition synthetic diamond: materials, technology and applications.

Abstract: Substantial developments have been achieved in the synthesis of chemical vapour deposition (CVD) diamond in recent years, providing engineers and designers with access to a large range of new diamond materials. CVD diamond has a number of outstanding material properties that can enable exceptional performance in applications as diverse as medical diagnostics, water treatment, radiation detection, high power electronics, consumer audio, magnetometry and novel lasers. Often the material is synthesized in planar form; however, non-planar geometries are also possible and enable a number of key applications. This paper reviews the material properties and characteristics of single crystal and polycrystalline CVD diamond, and how these can be utilized, focusing particularly on optics, electronics and electrochemistry. It also summarizes how CVD diamond can be tailored for specific applications, on the basis of the ability to synthesize a consistent and engineered high performance product.

Plasmon-enhanced single photon emission from a nanoassembled metal-diamond hybrid structure at room temperature.

Abstract: In this Letter we present the controlled coupling of a single nitrogen vacancy center to a plasmonic structure. With the help of an atomic force microscope, a single nanodiamond containing a single nitrogen vacancy center and two gold nanospheres are assembled step-by-step. We show that both the excitation rate and the radiative decay rate of the color center are enhanced by about 1 order of magnitude, while the single photon character of the emission is maintained. Hot spots between diamond and gold nanoparticles provide an efficient near-field coupling, despite the mismatch in size and shape. Our approach provides hybrid systems as important building blocks for novel nanophotonic light sources in advanced plasmonic devices stable even at room temperature.

Dynamic Polarization of Single Nuclear Spins by Optical Pumping of Nitrogen-Vacancy Color Centers in Diamond at Room Temperature

Abstract: We report a versatile method to polarize single nuclear spins in diamond, based on optical pumping of a single nitrogen-vacancy (NV) defect and mediated by a level anticrossing in its excited state. A nuclear-spin polarization higher than 98% is achieved at room temperature for the 15N nuclear spin associated with the NV center, corresponding to microK effective nuclear-spin temperature. We then show simultaneous initialization of two nuclear spins in the vicinity of a NV defect. Such robust control of nuclear-spin states is a key ingredient for further scaling up of nuclear-spin based quantum registers in diamond.

Boron-doped diamond electrode: synthesis, characterization, functionalization and analytical applications.

Abstract: In recent years, conductive diamond electrodes for electrochemical applications have been a major focus of research and development. The impetus behind such endeavors could be attributed to their wide potential window, low background current, chemical inertness, and mechanical durability. Several analytes can be oxidized by conducting diamond compared to other carbon-based materials before the breakdown of water in aqueous electrolytes. This is important for detecting and/or identifying species in solution since oxygen and hydrogen evolution do not interfere with the analysis. Thus, conductive diamond electrodes take electrochemical detection into new areas and extend their usefulness to analytes which are not feasible with conventional electrode materials. Different types of diamond electrodes, polycrystalline, microcrystalline, nanocrystalline and ultrananocrystalline, have been synthesized and characterized. Of particular interest is the synthesis of boron-doped diamond (BDD) films by chemical vapor deposition on various substrates. In the tetrahedral diamond lattice, each carbon atom is covalently bonded to its neighbors forming an extremely robust crystalline structure. Some carbon atoms in the lattice are substituted with boron to provide electrical conductivity. Modification strategies of doped diamond electrodes with metallic nanoparticles and/or electropolymerized films are of importance to impart novel characteristics or to improve the performance of diamond electrodes. Biofunctionalization of diamond films is also feasible to foster several useful bioanalytical applications. A plethora of opportunities for nanoscale analytical devices based on conducting diamond is anticipated in the very near future

High yield fabrication of fluorescent nanodiamonds

Abstract: A new fabrication method to produce homogeneously fluorescent nanodiamonds with high yields is described. The powder obtained by high energy ball milling of fluorescent high pressure, high temperature diamond microcrystals was converted in a pure concentrated aqueous colloidal dispersion of highly crystalline ultrasmall nanoparticles with a mean size less than or equal to 10 nm. The whole fabrication yield of colloidal quasi-spherical nanodiamonds was several orders of magnitude higher than those previously reported starting from microdiamonds. The results open up avenues for the industrial cost-effective production of fluorescent nanodiamonds with well-controlled properties.

Beamline I11 at Diamond: a new instrument for high resolution powder diffraction.

Abstract: The performance characteristics of a new synchrotron x-ray powder diffraction beamline (I11) at the Diamond Light Source are presented. Using an in-vacuum undulator for photon production and deploying simple x-ray optics centered around a double-crystal monochromator and a pair of harmonic rejection mirrors, a high brightness and low bandpass x-ray beam is delivered at the sample. To provide fast data collection, 45 Si(111) analyzing crystals and detectors are installed onto a large and high precision diffractometer. High resolution powder diffraction data from standard reference materials of Si, α-quartz, and LaB6 are used to characterize instrumental performance.

Turning carbon nanotubes from exceptional heat conductors into insulators.

Abstract: Thermal conductivity ($\ensuremath{\kappa}$) of isolated carbon nanotubes (CNTs) is higher than the $\ensuremath{\kappa}$ of diamond; however, in this Letter we show that the $\ensuremath{\kappa}$ of a packed bed of three-dimensional random networks of single and multiwall CNTs is smaller than that of thermally insulating amorphous polymers. The thermoelectric power ($\ensuremath{\Sigma}$) of the random network of CNTs was also measured. The $\ensuremath{\Sigma}$ of a single wall nanotube network is very similar to that of isolated nanotubes and, in contrast with $\ensuremath{\kappa}$, $\ensuremath{\Sigma}$ shows a strong dependence on the tube diameter.

Ultimate metastable solubility of boron in diamond: synthesis of superhard diamondlike BC5.

Abstract: The acknowledgment to L. Dubrovinsky for microprobe analysis was an error. On page 2, the statement that ‘‘The 1:5 boron-to-carbon ratio has been additionally confirmed by electron energy loss spectroscopy (GIF2000, Gatan) and by electron microprobe analysis (Cameca SX-50, Camebax)'' should read ‘‘The 1:5 boron-to-carbon ratio has been additionally confirmed by electron energy loss spectroscopy (GIF2000, Gatan) and by x-ray electron probe microanalysis (S400, Leica/PGT Spirit).'' In the caption of Fig. 1(b), the following remark should be added: ‘‘For clarity, the lines of rhenium from a gasket and lines of sodium chloride separating the sample from diamonds have been subtracted from the diffraction patterns.'' We also take an opportunity to add a missing sentence in the paragraph devoted to the electrical properties of c-BC5 on page 4: ‘‘Recently, diamondlike BC5 has been predicted to be metallic and superconducting with a Tc of 45 K [1].'' None of the results and conclusions in the Letter is affected by this negligence.

Nanodiamond-Polymer Composite Fibers and Coatings

Abstract: While nanocrystalline diamond is quickly becoming one of the most widely studied nanomaterials, achieving a large fraction of diamond nanoparticles in a polymer coating has been an unresolved problem. In this work, polymer nano- and microfibers containing high loadings of 5 nm diamond particles (up to 80 wt % in polyacrylonitrile and 40% in polyamide 11) have been demonstrated using electrospun nanofibers as a delivery vehicle. The electrospun nanofibers with a high load of nanodiamond in the polymers were fused into thin transparent films, which had high mechanical properties; an improvement of 4 times for the Young's modulus and 2 times for the hardness was observed already at 20% nanodiamond in polyamide 11. These films can provide UV protection and scratch resistance to a variety of surfaces, especially in applications where a combination of mechanical, thermal, and dielectric properties is required.

Excited-state spectroscopy of single NV defects in diamond using optically detected magnetic resonance

Abstract: Using pulsed optically detected magnetic resonance techniques, we directly probe electron-spin resonance transitions in the excited-state of single nitrogen-vacancy (NV) color centers in diamond. Unambiguous assignment of excited state fine structure is made, based on changes of NV defect photoluminescence lifetime. This study provides significant insight into the structure of the emitting 3 E excited state, which is invaluable for the development of diamond-based quantum information processing.

Boron-Doped Diamond Film Electrodes—New Tool for Voltammetric Determination of Organic Substances

Abstract: This review with 194 references summarizes the recent progress in the development and applications of boron-doped diamond film electrodes in electroanalysis of organic compounds. It is based on the survey of 106 papers listed in a comprehensive table devoted to batch voltammetric and liquid flow amperometric methods using boron-doped diamond electrodes. The varieties in their construction, surface pre-treatment and electroanalytical methods used are discussed. Special attention is paid to miniaturized boron-doped diamond electrodes for in vitro/in vivo sensing, or electrochemical detection coupled to conventional or chip-based electrophoretic detection systems. Further, possibilities and limitations of surface modification are discussed.

Harder than diamond: superior indentation strength of wurtzite BN and lonsdaleite.

Abstract: Recent indentation experiments indicate that wurtzite BN (w-BN) exhibits surprisingly high hardness that rivals that of diamond Here we unveil a novel two-stage shear deformation mechanism responsible for this unexpected result We show by first-principles calculations that large normal compressive pressures under indenters can compel w-BN into a stronger structure through a volume-conserving bond-flipping structural phase transformation during indentation which produces significant enhancement in its strength, propelling it above diamond's We further demonstrate that the same mechanism also works in lonsdaleite (hexagonal diamond) and produces superior indentation strength that is 58% higher than the corresponding value of diamond, setting a new record

Thermal Conductivity of Diamond Composites

Abstract: A major problem challenging specialists in present-day materials sciences is the development of compact, cheap to fabricate heat sinks for electronic devices, primarily for computer processors, semiconductor lasers, high-power microchips, and electronics components. The materials currently used for heat sinks of such devices are aluminum and copper, with thermal conductivities of about 250 W/(m·K) and 400 W/(m·K), respectively. Significantly, the thermal expansion coefficient of metals differs markedly from those of the materials employed in semiconductor electronics (mostly silicon); one should add here the low electrical resistivity metals possess. By contrast, natural single-crystal diamond is known to feature the highest thermal conductivity of all the bulk materials studied thus far, as high as 2,200 W/(m·K). Needless to say, it cannot be applied in heat removal technology because of high cost. Recently, SiC- and AlN-based ceramics have started enjoying wide use as heat sink materials; the thermal conductivity of such composites, however, is inferior to that of metals by nearly a factor two. This prompts a challenging scientific problem to develop diamond-based composites with thermal characteristics superior to those of aluminum and copper, adjustable thermal expansion coefficient, low electrical conductivity and a moderate cost, below that of the natural single-crystal diamond. The present review addresses this problem and appraises the results reached by now in studying the possibility of developing composites in diamond-containing systems with a view of obtaining materials with a high thermal conductivity.

Low temperature studies of the excited-state structure of negatively charged nitrogen-vacancy color centers in diamond.

Abstract: We report a study of the $^{3}E$ excited-state structure of single negatively charged nitrogen-vacancy (NV) defects in diamond, combining resonant excitation at cryogenic temperatures and optically detected magnetic resonance. A theoretical model is developed and shows excellent agreement with experimental observations. In addition, we show that the two orbital branches associated with the $^{3}E$ excited state are averaged when operating at room temperature. This study leads to an improved physical understanding of the NV defect electronic structure, which is invaluable for the development of diamond-based quantum information processing.

Diamond anvil cell, 50th birthday

Abstract: The year 2008 marked the fiftieth birthday of the diamond anvil cell. Its birth took place when Alvin Van Valkenburg, while working with his colleagues, Charles E. Weir, Ellis R. Lippincott, and Elmer N. Bunting, first realized that he could look right through one of the diamond anvils and see a sample while it was at high pressure. In the following years, these scientists and many others adapted the diamond anvil cell to a wide variety of analytical techniques that have provided an impressive amount of information about materials at high pressures and high temperatures. But, virtually all of those techniques start with looking into the diamond anvil cell.

Electronic and optical properties of boron-doped nanocrystalline diamond films

Abstract: We report on the electronic and optical properties of boron-doped nanocrystalline diamond (NCD) thin films grown on quartz substrates by CH4/H2 plasma chemical vapor deposition. Diamond thin films with a thickness below 350 nm and with boron concentration ranging from 1017 to 1021 cm−3 have been investigated. UV Raman spectroscopy and atomic force microscopy have been used to assess the quality and morphology of the diamond films. Hall-effect measurements confirmed the expected p-type conductivity. At room temperature, the conductivity varies from 1.5×10−8 Ω−1 cm−1 for a nonintentionally doped film up to 76 Ω−1 cm−1 for a heavily B-doped film. Increasing the doping level results in a higher carrier concentration while the mobility decreases from 1.8 down to 0.2 cm2 V−1 s−1. For NCD films with low boron concentration, the conductivity strongly depends on temperature. However, the conductivity and the carrier concentration are no longer temperature dependent for films with the highest boron doping and the NCD films exhibit metallic properties. Highly doped films show superconducting properties with critical temperatures up to 2 K. The critical boron concentration for the metal-insulator transition is in the range from 2×1020 up to 3×1020 cm−3. We discuss different transport mechanisms to explain the influence of the grain boundaries and boron doping on the electronic properties of NCD films. Valence-band transport dominates at low boron concentration and high temperatures, whereas hopping between boron acceptors is the dominant transport mechanism for boron-doping concentration close to the Mott transition. Grain boundaries strongly reduce the mobility for low and very high doping levels. However, at intermediate doping levels where hopping transport is important, grain boundaries have a less pronounced effect on the mobility. The influence of boron and the effect of grain boundaries on the optoelectronic properties of the NCD films are examined using spectrally resolved photocurrent measurements and photothermal deflection spectroscopy. Major differences occur in the low energy range, between 0.5 and 1.0 eV, where both boron impurities and the sp2 carbon phase in the grain boundaries govern the optical absorption.

CVD diamond for electronic devices and sensors

Abstract: Series Preface Preface List of Contributors Basic Properties, Defects and Impurities, Surface properties and Synthesis 1 Basic Properties of Diamond: Phonon Spectra, Thermal Properties, Band Structure ( Gordon Davies ) 2 Transport Properties of Electrons and Holes in Diamond ( Jan Isberg ) 3 Point Defects, Impurities and Doping ( Alison Mainwood ) 4 Surface Conductivity of Diamond ( Lothar Ley ) 5 Recent Progress in the Understanding of CVD Growth of Diamond ( JE Butler, A Cheesman and M N R Ashfold ) 6 Heteroepitaxial Growth ( M Schreck ) Radiation Sensors 7 Detectors for UV and Far UV Radiation ( Alan T Collins ) 8 Diamond Radiation Sensors for Radiotherapy ( Mara Bruzzi ) 9 Radiation Sensors for High Energy Physics Experiments ( H Kagan and W Trischuk ) 10 CVD-Diamond Detectors for Experiments with Hadrons, Nuclei, and Atoms ( E Berdermann and M Ciobanu ) 11 Neutron Detectors ( G Verona-Rinati ) Active Electronic Devices 12 High-Power Switching Devices ( Jan Isberg ) 13 H-Terminated Diamond Field-Effect Transistors ( Makoto Kasu ) 14 Doped Diamond Electron Devices ( E Kohn and A Denisenko ) 15 Optoelectronic Devices Using Homoepitaxial Diamond p - n and p - i - n Junctions ( Toshiharu Makino and Hiromitsu Kato ) Electrochemical and Biological Sensors 16 Biofunctionalization of Diamond Surfaces: Fundamentals and Applications ( J A Garrido ) 17 Diamond Electrochemical Sensors ( John S Foord ) Micro-Electro-Mechanical Systems 18 CVD Diamond MEMS ( J Kusterer and E Kohn ) Superconductivity in CVD Diamond 19 Superconductivity in Diamond ( Yoshihiko Takano ) Index

Understanding the chemical vapor deposition of diamond: recent progress.

Abstract: In this paper we review and provide an overview to the understanding of the chemical vapor deposition (CVD) of diamond materials with a particular focus on the commonly used microwave plasma-activated chemical vapor deposition (MPCVD). The major topics covered are experimental measurements in situ to diamond CVD reactors, and MPCVD in particular, coupled with models of the gas phase chemical and plasma kinetics to provide insight into the distribution of critical chemical species throughout the reactor, followed by a discussion of the surface chemical process involved in diamond growth.

Theory of spin-conserving excitation of the N-V(-) center in diamond.

Abstract: The negatively charged nitrogen-vacancy defect in diamond is an important atomic-scale structure that can be used as a qubit in quantum computing and as a marker in biomedical applications. Its usefulness relies on the ability to optically excite electrons between well-defined gap states, which requires a clear and detailed understanding of the relevant states and excitation processes. Here we show that by using hybrid density-functional-theory calculations in a large supercell we can reproduce the zero-phonon line and the Stokes and anti-Stokes shifts, yielding a complete picture of the spin-conserving excitation of this defect.

Fundamental investigation of subsurface damage in single crystalline silicon caused by diamond machining

Abstract: Single crystalline silicon was plunge-cut using diamond tools at a low speed. Cross-sectional transmission electron microscopy and laser micro-Raman spectroscopy were used to examine the subsurface structure of the machined sample. The results showed that the thickness of the machining-induced amorphous layer strongly depends on the tool rake angle and depth of cut, and fluctuates synchronously with surface waviness. Dislocation activity was observed below the amorphous layers in all instances, where the dislocation density depended on the cutting conditions. The machining pressure was estimated from the micro-cutting forces, and a subsurface damage model was proposed by considering the phase transformation and dislocation behavior of silicon under high-pressure conditions.

Chip-based microcavities coupled to NV centers in single crystal diamond

Abstract: Optical coupling of nitrogen vacancy centers in single-crystal diamond to an on-chip microcavity is demonstrated. The microcavity is fabricated from a hybrid gallium phosphide and diamond material system, and supports whispering gallery mode resonances with spectrometer resolution limited Q > 25000.

Fabrication of boron-doped diamond nanorod forest electrodes and their application in nonenzymatic amperometric glucose biosensing.

Abstract: A boron-doped diamond nanorod forest (BDDNF) electrode has been fabricated by hot filament chemical vapor deposition (HFCVD) method. This BDDNF electrode exhibits very attractive electrochemical performance compared to conventional planar boron-doped diamond (BDD) electrodes, notably improved sensitivity and selectivity for biomolecule detection. The BDDNF electrode, with the possibility of fabricating a sensitive biosensor for glucose without any catalyst or mediators, shows good activity toward direct detection of glucose by simply putting the bare BDDNF electrode into the glucose solution. Furthermore, the marked selectivity of the BDDNF electrode is very favorable for the determination of glucose in the presence of ascorbic acid (AA) and uric acid (UA). The robust sensitive and selective responses of this nanostructure indicate the promise of this kind of diamond electrode for real applications.

Printable, flexible and stretchable diamond for thermal management

Abstract: Various heat-sinked components and methods of making heat-sinked components are disclosed where diamond in thermal contact with one or more heat-generating components are capable of dissipating heat, thereby providing thermally-regulated components. Thermally conductive diamond is provided in patterns capable of providing efficient and maximum heat transfer away from components that may be susceptible to damage by elevated temperatures. The devices and methods are used to cool flexible electronics, integrated circuits and other complex electronics that tend to generate significant heat. Also provided are methods of making printable diamond patterns that can be used in a range of devices and device components.

Three-dimensional stimulated emission depletion microscopy of nitrogen-vacancy centers in diamond using continuous-wave light.

Abstract: Charged nitrogen-vacancy (NV) color centers in diamond are excellent luminescence sources for far-field fluorescence nanoscopy by stimulated emission depletion (STED). Here we show that these photostable color centers can be visualized by STED using simple continuous-wave or high repetition pulsed lasers (76 MHz) at wavelengths >700 nm for STED. Furthermore, we show that NV centers can be imaged in three dimensions (3D) inside the diamond crystal and present single-photon signatures of single color centers recorded in high density samples, demonstrating a new recording scheme for STED and related far-field nanoscopy approaches. Finally, we exemplify the potential of using nanodiamonds containing NV centers as luminescence tags in STED microscopy. Our results offer new experimental avenues in nanooptics, nanotechnology, and the life sciences.

Superconducting group-IV semiconductors.

Abstract: Despite the amount of experimental and theoretical work on doping-induced superconductivity in covalent semiconductors based on group IV elements over the past four years, many open questions and puzzling results remain to be clarified. The nature of the coupling (whether mediated by electronic correlation, phonons or both), the relationship between the doping concentration and the critical temperature (T(c)), which affects the prospects for higher transition temperatures, and the influence of disorder and dopant homogeneity are debated issues that will determine the future of the field. Here, we present recent achievements and predictions, with a focus on boron-doped diamond and silicon. We also suggest that innovative superconducting devices, combining specific properties of diamond or silicon with the maturity of semiconductor-based technologies, will soon be developed.