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CVD Diamond (cvd + diamond)
Selected AbstractsThe Influence of Doping Levels and Surface Termination on the Electrochemistry of Polycrystalline DiamondELECTROANALYSIS, Issue 6 2004Matthew Abstract The influence of surface chemistry and boron doping density on the redox chemistry of Fe(CN) at CVD polycrystalline diamond electrodes is considered. It is demonstrated that for this couple both the doping density and the surface chemistry are important in determining the rate of charge transfer at the electrode/electrolyte interface. For hydrogen terminated CVD diamond metallic electrochemical behavior is always observed, even at boron doping densities as low as 7×1018,cm,3. In contrast, the electrochemical behavior of oxygen terminated CVD diamond varies with doping density, a metallic response being observed at high doping density and semiconductor behavior at low doping density. It is shown that the results attained may be explained by a surface state mediated charge transfer mechanism, thus demonstrating the importance of controlling surface chemistry in electroanalytical applications of diamond. [source] Comparative study of TL created in undoped CVD diamond by , rays, UV and visible lightPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 9 2010V. Chernov Abstract The thermoluminescence (TL) properties of CVD diamond film irradiated with , rays and illuminated with UV and visible light (200,450,nm) have been studied. The film (23,µm) was grown for 47,h on monocrystalline silicon. The TL glow curves are similar for , irradiation and short wavelength UV light. The , dose response curves and UV light time response curves exhibit linear,supralinear,sublinear behaviour. The structure of the glow curve was determined by a simultaneous deconvolution of a set of curves recorded after preliminary heating to various temperatures. One set of the TL peak parameters was found for all the curves during the deconvolution. The TL glow curves were found to consist of five strongly overlapped peaks. The peaks at about 350 and 400,K obey first-order kinetics. The next three peaks at about 480, 540 and 580,K are described well by general-order kinetics. The TL curves created with light of wavelength between 250 and 450,nm are different from those created by , radiation and short wavelength UV light. The former have low sensitivity and consist of several strongly overlapped peaks, two of them are observed at about 330 and 600,K. [source] Position-sensitive radiation detectors made of single crystal CVD diamondPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 9 2009M. Pomorski Abstract Based on a single crystal chemical vapour deposition (scCVD) diamond plate a position sensitive detector [position sensitive detection position sensitive detector (PSD)] has been fabricated. The ,9,mm2 sensing area of the detector consists of a diamond-like carbon (DLC) thin film, in the form of a plane-pad resistive electrode layer deposited on the scCVD surface. The 1D position information is obtained from the resistive charge division between two collecting electrodes located at the extremities of the DLC sensing electrode. The detector properties have been tested using a 241Am ,-particles source. The timing characteristics of the device were probed using broad-band (BB) electronics: the signal formation does not exceed 30,ns, thus detector operation with a negligible ballistic effect is possible at high rates approaching 107,particles/s. The linearity and position resolution of the device was measured using low-noise charge-sensitive (CS) electronics: the position resolution reaches 30,µm (,), the deviation from linearity remain below 2% in the full range of the detector sensing area. [source] Compensation in boron-doped CVD diamondPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 9 2008Markus Gabrysch Abstract Hall-effect measurements on single crystal boron-doped CVD diamond in the temperature interval 80,450 K are presented together with SIMS measurements of the dopant concentration. Capacitance,voltage measurements on rectifying Schottky junctions manufactured on the boron-doped structures are also presented in this context. Evaluation of the compensating donor (ND) and acceptor concentrations (NA) show that in certain samples very low compensation ratios (ND/NA below 10,4) have been achieved. The influence of compensating donors on majority carrier transport and the significance for diamond device performance are briefly discussed. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Afterglow and thermally stimulated luminescence induced by UV radiation in CVD diamondPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 9 2007M. Barboza-Flores Abstract Afterglow (AG) and thermoluminescence (TL) of CVD diamond UV-irradiated with wavelength of 200,260 nm at room temperature are reported. The AG curves monotonously decrease with time and are fitted well by the hyperbolic law. The decay times depends on UV wavelength and decreases with the AG intensity increasing. The TL glow curves exhibit two pronounced TL peaks with maxima at about 350 K and 513 K with unstructured signal between them and are fitted well by four TL peaks. The first, 350 K peak with the activation energy of 0.59 eV was supposed to be second kinetics order. The higher temperature peaks at 402 K, 445 K and 513 K with the activation energies of 0.46 eV, 0.49 eV and 0.68 eV, respectively were assumed to be first kinetics order. The comparison of the AG decay times with the kinetics parameters of the 350 K TL peak proved that AG is caused by thermal emptying of the traps responsible for the 350 K peak. The behaviour of AG and 350 K TL peak was described by the model, in which shallow traps, recombination centers and deep thermally disconnected traps are taken into account. The AG and TL creation spectra are practically the same and consists of a broad band, which exponentially increases from 260 nm, reaches a maximum at 240 nm and then begins decreasing. The creation spectra of the AG and TL peaks are the same and closely related with the fundamental absorption of UV light near indirect band gap of diamond. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Thick single crystal CVD diamond prepared from CH4 -rich mixturesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 12 2006G. Bogdan Abstract Recent interests in freestanding single-crystal CVD diamond (SC-CVD) discs for several applications in electronics led to an intense study of SC-CVD layer growth and properties. In this work we have investigated the growth mechanism of monocrystalline CVD diamond films with surfaces smooth in nanometer scale taking into account the defect incorporation in the SC-CVD layers. Specifically we discuss the surface structure characteristics for these conditions as studied with high-resolution AFM mapping. The as-grown CVD layers were removed from the substrate by laser cutting, followed by a polishing step, yielding freestanding plates. Subsequently, microscopic and colour studies as well as infrared absorption spectroscopy were performed. These investigations revealed the presence of several characteristic defects and impurities. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Carbon nanodots made on diamond surface by focused ion beamPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2006Alexander M. Zaitsev Abstract Carbon nanodots were made on the polished surface of a single crystal CVD diamond by a focused 30 keV Ga+ ion beam. The electrical conductance via the nanodots was measured in two types of structures: single nanodots embedded in the gaps of broken carbon nanowires and linear chains of nanodots. Changes of the conductance with annealing temperature allow to make the conclusion that the size of the electrically conductive area of the nanodots increases from a few nanometers to 20 nm after annealing from 500 to 1000 °C. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Electron spin resonance characterization of phosphorus-doped CVD diamond filmsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 11 2004M. Katagiri Abstract Electron spin resonance technique has been applied to characterize defects and to determine local structure of phosphorus in phosphorus-doped (111)-homoepitaxially grown CVD diamond films. Dominant defects have g -value similar to that of the H1 center in polycrystalline CVD diamond, however, are not accompanied with a unique nearby hydrogen atom. These defects are likely to be located near substrate/ epilayer interface. New phosphorus related center with a tetragonal symmetry has been found. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] 2D mapping of the response of CVD diamond X-ray detectors: defects and device dynamicsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 11 2004M. J. Guerrero Abstract To investigate the influence of intrinsic defects in polycrystalline CVD diamond, we have used a micro-focused X-ray beam to induce local photo-currents in solid state ionisation chambers. The device behaviour was studied as a function of the defect level populations. This microscopic study of the X-ray sensitivity was then performed using varying initial states of the devices as well as varying device temperatures. These measurements, coupled with the study of the temporal evolution of the photocurrent as a function of the temperature, seemed to demonstrate the existence of highly localised regions that may detrimentally affect the overall device response. This may demonstrate that the imperfections CVD diamond devices exhibit may be caused by extremely localised point defects. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Analysis of traps in CVD diamond films through thermal depumping of nuclear detectorsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 11 2004A. Balducci Abstract Carrier free paths in Chemical Vapour Deposition (CVD) diamond films depend on the presence of traps, which therefore strongly affect the performance of those CVD diamond based devices which rely on the electronic properties of the material, like radiation detectors. For the same reason, these devices can in turn be used as tools to study carrier dynamics. It is well known that some traps may be saturated by pre-irradiation with ionizing radiation (e.g. ,-particles), a process called "pumping" or "priming". Not all traps behave in the same way. Due to the large bandgap of diamond, both shallow (not affected by pumping) and deep traps for electrons and holes may exist. We measured, using 5.5 MeV 241Am ,-particles, the response of high quality CVD diamond based detectors after successive annealing steps performed at selected temperatures. The analisys of the decay of the detector efficency with annealing time at several temperatures allows a quantitative evaluation of the activation energy of these defects. Two main trapping centres connected to the pumping process were found, both related to holes, having activation energies of about 1.6 eV and 1.3 eV respectively. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Alternating-current conductance and capacitance of a diamond diode in the presence of deep-level impuritiesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2010Ana Rodrigues Abstract The alternating-current conductance and capacitance of a diamond film/aluminium diode was measured over the temperature range 230,330 K. Loss tangent curves for the frequency range 100 Hz,1 MHz exhibited three maxima. Doping of the CVD diamond was not uniform, indicating the presence of deep-level impurities. Results were analysed for the temperature range 230,270 K, at which it is possible to observe processes that are supposed to occur in grains and grain boundary regions of polycrystalline diamond. A loss tangent curve was simulated using an equivalent circuit model composed of resistances and capacitances corresponding to depletion regions and the bulk and of the electrical characteristics of the two phases of diamond. This model explicitly includes deep impurities. The curve-fitting parameters for the loss tangent plot demonstrate that at medium frequency (4 kHz, activation energy 0.2 eV) the bulk resistance is high (100 k,) and the maximum is related to the presence of microcrystals, which exhibit low conductivity. At high frequency (800 kHz, activation energy 0.5 eV) the bulk resistance is low (1 k,), suggesting that the maximum is associated with grain boundary regions. The low values of the relaxation times obtained (10,28 and 4×10,27 s) are justified. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Determination of carrier diffusion coefficient and lifetime in single crystalline CVD diamonds by light-induced transient grating techniquePHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 9 2010T. Malinauskas Abstract We report on a contactless, all-optical study of carrier diffusion and recombination kinetics in single-crystalline diamond layers using the light-induced transient grating (LITG) technique. Decay times of transient diffraction grating yielded carrier lifetime of ,R,,,3,ns and bipolar diffusion coefficient Da,=,12,cm2/s at 300,K. The latter value of Da was found to be 4,5 times lower than the ambipolar diffusivity based on electron and hole mobilities, measured by photo-electrical time-of-flight (ToF) technique. This discrepancy was attributed to the bandgap renormalization at high excess carrier densities and its impact on carrier diffusion. The significant decrease of low temperature diffusivity pointed out to a contribution of many-body effects which are tentatively attributed to the formation of electron,hole liquid (EHL) at T,<,150,K. [source] | ||||||||||