bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of a Thick Homoepitaxial CVD Diamond Film
Authors: Plano M. A. , Moyer M. D. , Moreno M. M. , Black D. , Burdette H. , Robins L. , Pan L. S. , Kania D. R. , Banholzer W. 
Published: April 2011

ABSTRACTA thick homoepitaxial CVD diamond film was grown on a large high temperature, high pressure (HTHP) Ha diamond to study the defects present in the CVD film. The HTHP diamond had dimensions of 6 mm x 6 mm x 0.44 mm. The thickness of the diamond was increased to 0.84 mm by microwave plasma CVD. X-ray topographs were taken before and after growth to compare the defects in CVD diamond to those in the HTHP diamond. Prior to growth the substrate was unstrained and the characteristic microstructure of stacking faults and dislocations was observed. There was also a surface relief, visible optically, on the substrate of lines along the [100] which are probably due to polishing. After deposition of the CVD film, the crystal was strained with the film in tension. The defect structure observed throughout the CVD film followed the surface relief of the substrate. Cathodoluminescence spectra indicate that the film contains nitrogen defect complexes which are not present in the substrate. Cathodoluminescence also indicates that there are more non-radiative recombination centers in the film than in the substrate. Electrical results from transient photoconductivity measurements indicate that while the mobilities of the film and the substrate are comparable, the lifetime is much shorter in the film, possibly reflecting the higher concentration of non-radiative recombination centers.
Cathodoluminescence Spectroscopy of Boron Nitride Films
Authors: Taylor C. A. , Brown S. W. , Subramaniam V. , Kidner S. , Rand S. C. , Clarke R. 
Published: April 2011

ABSTRACTWe report results from cathodoluminescence spectroscopy of boron nitride films grown on Si (100) substrates by ECR ion source assisted magnetron sputtering of a hexagonal BN target. Three main peaks are observed in the near-bandgap region for hexagonal boron nitride films at energies of 4.90 eV, 5.31 eV, and 5.50 eV. In addition, deep-level emission spectra of predominantly cubic boron nitride films are correlated with sample growth conditions. In particular we show that the emission intensity, position, and linewidth are strongly dependent on the substrate bias voltage used during sample growth.
Low Energy Threshold in the Growth of Cubic Boron Nitride Films by ECR Plasma Assisted Magnetron Sputtering
Authors: Taylor C. A. , Kidner S. , Clarke R. 
Published: April 2011

ABSTRACTWe report the growth of cubic boron nitride (cBN) films by magnetron sputtering on Si (100) substrates. The films are grown in the presence of negative substrate bias voltages and a nitrogen plasma produced by an electron cyclotron resonance source. We find evidence for a sharp low-voltage threshold in the substrate bias (-105 V) beyond which the samples are predominantly cBN. The structural quality of the cBN films is optimized in a narrow range of voltages near this threshold. We discuss the important role of energetic ions in the formation of cBN in light of recent theoretical findings.
Nucleation and Step Dynamics in SIC Epitaxial Growth
Authors: Atsunami Hiroyuki , Kimoto Tsunenobu 
Published: April 2011

ABSTRACTRecent progress in horaoepitaxial growth of 6H-SiC by stop-controlled epitaxy utilizing off-angle substrates is discussed in detail. Features of step-controlled epitaxy and its growth mechanism are described based on experimental results. The growth mode on off-angle substrates is explained by a stagnant layer model. The diffusion length of adatoms on a surface is calculated using a simple surface diffusion model. The critical conditions of two-dimensional nucleation and step-flow growth are predicted based on theoretical calculation and experimental results. Microscopic surface processes such as nucleation and step motion are made clear by observing the grown layer after short-time growth.
Growth of Epitaxial 2H-silicon Carbide by Pulsed Laser Deposition
Authors: Stan Mark A. , Patton Martin O. , Vithana Hemasiri K. M. , Johnson David L. , Warner Joseph D. , Piltch Nancy D. , Yang Jinwei , Pirouz Pirouz 
Published: April 2011

ABSTRACTSilicon carbide films have been grown on 6H-SiC (0001) and Si (001) wafers by laser ablation using an excimer laser. The films were deposited at heater plate temperatures between 970° C to 1270° C. Film composition, morphology and polytypism were determined by Auger electron spectroscopy, atomic force microscopy and high resolution transmission electron microscopy (TEM). In the course of these experiments growth of 2H-SiC on 6H-SiC was observed at the highest heater plate temperatures. Cross-sectional TEM images clearly show the symmetry of a film grown at 1270° C as c-axis oriented 2H-SiC containing columnar grains with average diameter of 20 nm and length of 100 nm.
Dynamics of the Nitrogen Bound Excitons in 6H and 3C SiC
Authors: Bergman J. P. , Harris C. I. , Kordina O. , Henry A. , Janzén E. 
Published: April 2011

AbstractWe have measured the photoluminescence decay time of the bound excitons at the neutral nitrogen donors in the 6H and 3C polytypes of SiC. At 2K the decay times are 8.0 ns, 1.8 ns and 1.5 ns, for the P, R and S bound excitons in 6H SiC. For the nitrogen exciton in 3C, we find a decay time of 160 ns. These values are faster than previously reported for shallow donors in other indirect bandgap materials such as Si or GaP. Each of the observed decay times is found to be independent of the doping level in the sample, is temperature independent at low temperatures but decrease when the bound excitons are thermally ionised. The decay time related to different donor levels in 6H exhibits a strong dependence on the donor binding energy. We suggest that the dominant mechanism responsible for the observed decay time is a phonon-less Auger process. In high-purity 6H samples we have also measured the free exciton decay time at low temperatures to be 12 ns.
The Effects of Friction and Wear on PECVD Diamond Films.
Authors: Languell M. L. , Davidson J. L. , Wert J. J. , George M. A. , Collins W. E. , Burger A. 
Published: April 2011

ABSTRACTThe effects of friction and wear were examined on plasma enhanced chemical vapor deposition (PECVD) diamond films deposited on tungsten substrates. The tribology of diamond on diamond was studied and the changes in surface roughness and the bearing ratio were determined before and after wear. The (111) textured heteroepitaxial films were studied morphologically by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The changes in morphology involved a transition from the large as grown diamond crystallites with a mean diameter of 10 μm to a surface with grains as small as 100 nm. The nature of the wear-modified films will be discussed regarding the possible mechanisms for the surface changes.Work partially supported by NASA Lewis Research Center grant NAG3–1430.
On the Nature of the Native Defect ESR in Thin Diamond Films
Authors: Shinar J. , Jia H. , Lang D. P. , Pruski M. 
Published: April 2011

ABSTRACTThe X-band ESR of thin diamond films deposited from 99.5% H2/0.5% CH4 is compared to that of films similarly prepared from D2CD4 and H2/13CH4. The main line and the satellites at ±7.2 G are unaffected by annealing at T <. 1100°C, but their intensity is reduced upon annealing at T ∼ 1200°C. As the satellites are absent from the deuterated films, they are attributed to newly identified dangling bond-H centers, either on internal microvoid surfaces or embedded in the tetrahedral network. This is consistent with the 13C spin-lattice relaxation rate, which indicates that the distribution of paramagnetic centers is homogeneous to within ∼0.04 μm. However, they may be nonuniformly distributed on a finer scale, consistent with the concentrations in m ulti vacancies or stacking faults recently suggested by Fanciulli and Moustakas.
On the Structure of Thin diamond Films: A 1H and 13C Nuclear Magnetic Resonance Study
Authors: Shinar J. , Pruski M. , Lang D. P. , Hwang S.-J. , Jia H. 
Published: April 2011

ABSTRACTThe 1H and 13C nuclear magnetic resonance (NMR) of thin diamond films deposited from naturally abundant (1.1 at.%) as well as 50% and 100% 13C-enriched CH4 heavily diluted in H2is described and discussed. Less than 0.6 at.% of hydrogen is found in the films which contain crystallites up to ∼15 μm across. The 1H NMR consists of a broad 50–65 kHz wide Gaussian line attributed to H atoms bonded to carbon and covering the crystallite surfaces. A narrow Lorentzian line was only occasionally observed and found not to be intrinsic to the diamonds. The 13C NMR demonstrates that >99.5% of the C atoms reside in a quaternary diamond-like configuration. The 13C spin-lattice relaxation times T1 are four orders of magnitude shorter than in natural diamond and believed to be due to 13C spin diffusion to paramagnetic centers, presumably carbon dangling bonds. Analysis of T1 indicates that within the 13C spin diffusion length of ∼0.05 μm these centers are uniformly distributed in the diamond crystallites, possibly concentrated on the internal surfaces of a relatively dense system of nanovoids.
Radiation Defects in SiC - Electron Irradiation With Different Energies
Authors: Volm D. , Meyer B. K. , Mokhov E. N. , Baranov P. G. 
Published: April 2011

ABSTRACTRadiation defects in 6H SiC introduced by electron irradiation at energies of 400 keV and 1 MeV are studied by low-temperature photoluminescence and Zeeman spectroscopy. We observe a new two line spectrum at 2.547 and 2.528 eV which dominates in the spectrum of the sample irradiated at 400 keV. For 1 MeV irradiation numerous recombination lines are observable and also the well known D1 center lines appear. Annealing the sample at 1100 °C leads to the disappearance of almost all lines but the D1 lines are still present.
Properties Of crystalline 3C-SIC Grown From Methyl Trichlorosilane
Authors: Moore W. J. , Kaplan R. , Freitas J. A. , Altaiskii Y. M. , Zuev V. L. , Ivanova L. M. 
Published: April 2011

ABSTRACTCubic silicon carbide grown by thermal decomposition of methyl trichlorosilane in hydrogen has been studied in infrared (IR) transmission, cyclotron resonance (CR), and photoluminescence (PL). Sample characteristics include: The nitrogen concentration, determined from CR and IR can be of the order of 1015 cm-3 or less. Ionized impurity concentrations determined from the linewidths of CR and IR spectra can be less than 7 × 1014 cm-3. Low temperature electron mobilities from CR are near 105 cm2 v-1 s-1. Carrier freeze-out is consistent with either uncompen-sated donors with activation energy near 50 meV or heavily compensated donors with 20 meV activation energy. The latter choice, however, is excluded by the low ionized impurity concentration. These high quality samples show little or no evidence of the apparently shallow (< ∼20 meV) donor which usually dominates the low temperature conductivity of 3C-SiC grown on Si. Nitrogen donor excitation spectra are in excellent agreement with effective mass theory. Only nitrogen donors at 54.2 meV and an unidentified effective-mass donor at 47.8 meV are observed. If material with the characteristics described above can be reliably reproduced then there is substantial expectation that high quality electronic devices based on 3C-SiC can be fabricated.
Growth of Beta Silicon Carbide Film on Si by Hot-Filament CVD
Authors: Rong Zhang , Hongtao Shi , Shidong Yu , Youdou Zheng , Yuliang He , Xiangna Liu 
Published: April 2011

ABSTRACTIn this paper, we will report fabrication and structure study of single crystal β-SiC film on Si substrate by hot-filament chemical vapor deposition (HFC VD). The reaction sources are hydrogen-diluted methane(CH4) and Silane(SiH4). The wafer surface temperature is about 650°C. The typical growth rate is 200nm/h. Raman scattering spectrum shows a peak centering at 960cm-1 with a full width at half magnitude (FWHM) of 75cm-1. At room temperature, the photoluminescence spectrum gives a wide band at 580nm (2.2eV) with a FWHM of 55nm. Fourier transmission infrared (FT-IR) spectrum exhibits an absorption peak at 12.6 μm XRD and XPS analysis indicate that the epilayer is a stoichiometrical single crystal cubic silicon carbide film.
Electron Emission Properties of the Negative Electron Affinity (111)2×1 Diamond-Tio Interface
Authors: Bandis C. , Haggerty D. , Pate B.B 
Published: April 2011

ABSTRACTWe report photoemission measurements from the (111)2×1 diamond-titanium monoxide (TiO) interface. Submonolayer deposition of TiO on the (111)2×1 diamond surface modifies the electron affinity of the surface from positive to negative. No change in the band bending was observed as a result of the TiO deposition. Total electron yield measurements from the diamond-TiO interface were also performed. The yield spectra, as expected for a negative electron affinity (NEA) surface, have emission thresholds that are in good agreement with the absorption coefficient of diamond. To further understand the emission properties of NEA (111) diamond surfaces we also compare the electron yield photo-excitation spectra of the diamond-TiO interface with the yield spectra of hydrogenated (111)1×1:H diamond surfaces.
Infrared Study of Trimethylgallium Adsorption on GaAs(100)
Authors: Gee Paul E. , Qi Haihua , Hicks Robert F. 
Published: April 2011

ABSTRACTTrimethylgallium (TMGa) adsorption on GaAs(100) has been studied by infrared spectroscopy. The adsorbed TMGa exhibits up to five C-H stretching vibrations between 2700 and 3000 cm−1 and five C-H deformations between 1100 and 1500 cm−1. The adsorbate uptake is a maximum at arsenic coverages of –65%. These and other results indicate that TMGa dissociatively adsorbs onto As dimers with methyl transfer to second-layer Ga atoms and to As atoms. Above 333 K, molecular desorption competes with adsorption, causing the saturation coverage to fall with increasing temperature. The desorption kinetics depend on the composition of the GaAs(100) surface. These kinetics suggest that above 773 K, TMGa is more likely to decompose on the c(2×8) than on a more Ga-rich surface.
Effect of Substrate Misonrentation on Ordering in Ga0.5In0.5P
Authors: Su L.C. , Ho I.H. , Stringfellow G.B. , Leng Y. , Williams C.C. 
Published: April 2011

ABSTRACTOrdering produced in Ga0.5ln0.5P epitaxial layers grown by OMVPE can be controlled by variations in the substrate misorientation as well as the growth temperature and the growth rate. The ordering produced at a growth temperature of 620°C and a relatively low growth rate of 0.5 μm/hr is found to depend strongly on both the direction and angle of substrate misorientation. Transmission electron microscope images and transmission electron diffraction (TED) patterns as well as electrostatic force microscopy (EFM) and photoluminescence (PL) has been studied for misorientation angles of 0, 3, 6, and 9° from (001) toward the (111)B, (111)A, and [010] directions in the lattice. Misorientation in the (111)B direction (to produce [110] steps) increases ordering for angles of up to approximately 4°. Increasing the misorientation angle in the (111)A direction actually leads to a decrease in the degree of order observed. Misorientation in the [010] direction also decreases the degree of order, although the effect is much less than observed for misorientation in the (111)A direction. The most highly ordered material produced under these growth conditions is for a misorientation angle of 3° in the (111)A direction. Increasing the growth temperature to 720°C produces completely disordered material. This wide variation in ordering behavior has allowed the growth of an order/disorder heterostructure for a substrate misorientation of 3° in the (111)A direction. The heterostructure consists of a Ga0.52In0.48P layer grown at 740°C followed by an ordered layer grown at 620°C. The x-ray diffraction results show that both layers are precisely lattice-matched to the GaAs substrate. TED patterns show that the first layer is completely disordered and the top layer is highly ordered, with only a single variant. EFM images of the order/disorder heterostructure show a pronounced contrast at the interface, attributed to the large difference in the nature of the surface states in the ordered and disordered materials. The 10 K PL spectrum consists of two sharp and distinct peaks at 1.995 and 1.830 eV from the disordered and ordered materials, respectively. The peak separation represents the largest energy difference between ordered and disordered materials reported to date. Such heterostructures may be useful for photonic devices.
Application of Selective Area MOVPE for DFB Gratings with Modulated Coupling Coefficient
Authors: Tidemand-Petersson Peer , Albrektsen Ole , Møller-Larsen Anders , Salzman Joseph 
Published: April 2011

ABSTRACTA new application of selective area metalorganic vapour phase epitaxy is demonstrated: fabrication of distributed feedback (DFB) gratings with sub-micron period and modulated coupling coefficient Kc. A SiO2 mask layer defines the InGaAs(P) grating pattern as well as the lateral variation in growth rate and, hence, thickness of the grating. In this way K can be varied along the laser cavity in a controlled and reproducible manner.
The Optimization of Interfaces in InAsSb/InGaAs Strained-Layer Superlattices grown by Metal-Organic Chemical Vapor Deposition
Authors: Biefeld R. M. , Baucom K. C. , Kurtz S. R. 
Published: April 2011

ABSTRACTWe have prepared InAsSb/InGaAs strained-layer superlattice (SLS) semiconductors by metal-organic chemical vapor deposition (MOCVD) using a variety of growth conditions. The presence of an InGaAsSb interface layer is indicated by the x-ray diffraction patterns. The optimized growth conditions involved the use of low pressure, short purge times between the growth of the layers, and no reactant flow during the purges. We used MOCVD to prepare an optically pumped, single heterostructure InAsSb/InGaAs SLS / InPSb laser which emitted at 3.9 μm with a maximum operating temperature of approximately 100 K.
Enhancement of Gold on n-InGaAs Schottky Barrier Height by Using a thin p-InP Layer
Authors: Yang Bing , Chen J. C. , Choa F. S. 
Published: April 2011

ABSTRACTIn this study, we demonstrate the enhancement of n-In0.53Ga0.47A s Schottky barrier height by using a thin (300-1800 Å) p-InP surface layer. An increase in the barrier height of 0.46 eV, making the total barrier height 0.66 eV, was obtained in a Au/p-InP/n-InGaAs structure, resulting in a great reduction of leakage currents. Results of the electrical measurements are summarized in table 1. The barrier height of n- In0.53Ga0.47As was increased from 0.2 eV to 0.66 eV when a 1200-Å-thick p-InP surface layer was employed.
Fermi Level Pinning in Au Schottky Barriers on InGaP and InGaAlP
Authors: Gorbyley V.A. , Chelniy A.A. , Chekalin A.A. , Polyakov A.Y. , Pearon S.J. , Smirnov N.B. , Gnorkov A.V. , Leiferov B.M. , Popova E.V. , Kusikov V.A. , Balmashnov A.A. 
Published: April 2011

ABSTRACTIt is shown that in Au/InGaP and Au/InGaAlP Schottky diodes the Fermi level is pinned by metal-deposition-induced midgap states. Hydrogen plasma treatment of such diodes greatly improves the reverse currents. The measured Schottky barrier heights seem to correlate with the valence band offsets measured by DLTS on quantum well structures.
The Use of Tetraethyltin as an N Type Dopant Source in GAAs, ALGAAs, and ALAS for Lasers and Bragg Reflectors Grown by MOCVD
Authors: Pinzone C. J. , Neff I. G. , Chelakara R. V. , Fertitta K. , Dupuis R. D. 
Published: April 2011

ABSTRACTThe use of Tetraethyltin (TESn) as a source of donors in GaAs and its A1xGal-xAs alloys with x varied from 0 to 1 has been investigated for the growth of heterostructures by low pressure metalorganic chemical vapor deposition. (LP-MOCVD). The donor activity increases in the binary and ternary alloys as a function of tetraethyltin molar flow fraction and with increasing temperature. High quality one quarter wave Distributed Bragg reflectors (DBRs) were grown with TESn as an n type dopant source with no degradation in reflectivity observed. No surface accumulation of tin was observed and the morphology of all epitaxial samples was excellent. Sn incorporation in AlAs produced n type material as determined by Van der Pauw Hall measurements. The use of TESn as a convenient and controllable dopant source in structures such as vertical cavity surface emitting lasers which incorporate DBRs as well as other heterostructure devices is therefore practical..
Growth Temperature Uniformity of MBE-Grown GaAs Determined by Scanning Room Temperature Photoluminescence
Authors: Stair K. , Bird T. , Moretti A. , Chambers F. , Choi-Feng C. 
Published: April 2011

ABSTRACTWe have used scanning room temperature photoluminescence to map GaAs quantum well widthsand AIGaAs barrier compositions over 2-inch and 3-inch diameter epitaxial layers grown by MBE at temperatures ranging from 600 to 700ºC. Analysis of these maps allows a nondestructive quantitative analysis of the GaAs growth rate uniformity from which we can calculate the temperature distribution during growth. We have used this technique to compare the thermal uniformity of various substrate holders designed for use in the Intevac ModGenII MBE system.
Dopant and As4/Ga Flux Ratio Influence on the Electrical and Structural Properties of LT GaAs
Authors: O'Hagan S. P. , Missous M. 
Published: April 2011

ABSTRACTDouble crystal x-ray diffraction and Hall effect measurements have been performed on GaAs layers grown by molecular beam epitaxy at low substrate temperature (200-250°C). The concentration of excess As incorporated in undoped material is found to be a strong function of growth temperature but not of As4/Ga beam equivalent pressure ratio at a given temperature. Doping with Si or Be at concentrations of 1019cm−3 or greater has resulted in significant reduction of excess As concentration in layers grown at 250'C. This effect is seen to diminish with reducing substrate temperature. The effect is not seen when Se is used as the doping source. Reducing As overpressure in the presence of such a high doping concentrations has led to highly electrically active n- and p-type layers grown at 250'C.
A Molecular Dynamics Study of InGaAs Layers on GaAs Substrates
Authors: Moran G J , Morrison I , Matthai C C 
Published: April 2011

ABSTRACTWe have performed molecular dynamics simulations of thin layers of InGaAs on GaAs substrates for different In concentrations to determine the critical thickness before strain relaxation occurs. We have considered both dislocation formation and islanding as possible mechanisms for strain relief. The results for the critical thickness for strain relief by misfit dislocations is slightly lower than that found using elasticity theory. For high In concentrations, facetted islands are found to be stable and are energetically favoured.
Optical Properties of Light-Hole Excitons in MOVPE Grown (Ga,In)As-GaAs Quantum Wells
Authors: Bigenwald P. , Laire O. , Zhang X. , Briot O. , Gil B. , Cloitre T. , Aulombard R.L. 
Published: April 2011

ABSTRACTWe study the optical properties of metalorganic vapour phase epitaxy (MOVPE) grown (Ga,In)As-GaAs single quantum wells as a function of the growth parameters. Our objective is to study the properties of the type II light-hole excitons with light-hole wave function delocalized in the thick GaAs layers and electrons confined in the ternary alloy. However, marked structures (like for type I excitons) are observed in the reflectivity spectra. This we interpret in the context of a novel approach of the exciton problem via a self-consistent calculation of the electron-hole interaction.