bluuebunny/crossref_metadata_2025_split huggingface dataset:
UV-Sensitive Metal-Semiconductor Photodiodes on 6H-SIC.
Authors: Fröjdh Christer , Thungström Göran , Nilsson Hans-Erik , Sture Petersson C. 
Published: April 2011

ABSTRACTSchottky diodes on Silicon Carbide (SiC) are of interest for many applications because of the relatively simple fabrication process. In this work we have fabricated Schottky diodes by evaporation of Ti on 6H-SiC and measured their electrical and optical properties. Most of the diodes show good rectifying behaviour with low reverse current and an ideality factor below 1.20. The photoresponse of the diodes has been measured in the range 200 – 400 nm. The peak sensitivity was found to be at 270 nm.
Metallization of GaN Thin Films Prepared by Ion Beam Assisted Molecular Beam Epitaxy
Authors: Chan J. S. , Fu T. C. , Cheung N. W. , Newman N. , Liu X. , Ross J. T. , Rubin M. D. , Chu P. 
Published: April 2011

AbstractGallium nitride has generated much interest due to its ability to emit light in the blue to UV range [1]. We have investigated the ohmic contact properties of various metals evaporated onto highly auto-doped n-type GaN thin films which were grown on basal sapphire substrates by ion-assisted molecular beam epitaxy (IAMBE). Electrical measurements of transmission line structures with the metals In, InSn and AuGeNi revealed a wide range of contact resistivity (10∼2 to 10-6 Ω-cm2) which changed with annealing.
Solid-Phase Reaction of Tungsten Thin Films with Polycrystalline Diamond
Authors: Bachli A. , Chen J. S. , Ruiz R. P. , Nicolet M-A. 
Published: April 2011

ABSTRACTThe thermally induced solid-phase reaction of 135 nm thick sputter-deposited W films with polycrystalline CVD-grown diamond substrates is investigated. The samples are annealed in vacuum (5×10/-7 torr) at temperatures between 700 °C and 1100 °C for 1 hour and examined by 2 MeV 4He++ backscattering spectrometry, x-ray diffraction, and scanning electron microscopy.The as-deposited W films contain roughly 5 at.% oxygen. After annealing the samples at 800 °C this oxygen concentration falls below the detection limit of less than 1 %. Incipient W2C phase formation occurs during annealing at 900 °C. The final state, the WC phase, is reached after annealing at 1100 °C.
Deposition of Epitaxially Oriented Films of Cubic SiC on Silicon by Laser Ablation of Elemental Targets.
Authors: Rimai L. , Ager R. , Weber W. H. , Hangas J. , Poindexter B. D. 
Published: April 2011

ABSTRACTSilicon carbide films are grown epitaxially on crystalline silicon substrates heated above 1000 °C, by laser ablation of pure carbon targets to thicknesses between 300 and 400 nm. These films grow on top of the silicon substrate from the carbon in the ablation plume and from the silicon of the substrate. By using a method of alternate ablation of a pure carbon and a pure silicon target, similar epitaxial films can be grown to thicknesses in excess of 1 μm with part of the silicon being supplied by the ablation plume of the silicon target.
Stacking Fault Energy Calculations in 6H- and 15R-SiC
Authors: Chien F. R. , Nutt S. R. , Yoo W. S. 
Published: April 2011

ABSTRACTAs-grown SiC single crystals and as-deposited SiC epilayers often exhibit stacking faults. The most probable fault configurations that occur in 6H- or 15R-SiC crystals are deduced from calculations of the stacking fault energies using a modified Ising model with the Ising parameters taken from earlier ab initio calculations. In this study, experimental TEM observations reveal stacking fault configurations in 6H- and 15R-SiC, and the observed configurations are compared with calculated stacking fault energies.
XPS and Sims Studies of CVD-GROWN Cubic SiC Films on Si(100)
Authors: Wee A. T. S. , Feng Z. C. , Hng H. H. , Tan K. L. , Tin C. C. , Hu R. , Coston R. 
Published: April 2011

ABSTRACTA series of CVD-grown 3C-SiC/Si(100) films of different growth times, and hence film thicknesses, are studied by X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). XPS showed that the surfaces of the samples consist of Si oxides (SiO2 and SiOx where x < 2) and unreacted C.H. Unreacted elemental Si is also present and its amount decreases with increasing growth time. This surface overlayer is further investigated by changing the photoelectron take-off angle and from chemical etching studies. Compositional variations of the SiC films are also studied using SIMS.
Reactive Magnetron Sputtering of Silicon in AR + CH4: Identity and Energy of the Slc Growth Species
Authors: Fitzner M. P. , Abelson J. R. 
Published: April 2011

ABSTRACTDouble-modulation mass spectrometry is used to analyze the identity and energy distribution of the particle flux during low-temperature growth of Si1−xCx by reactive magnetron sputtering of a silicon target in 3 mTorr argon and 0 – 0.35 mTorr methane. The ion fluxes, methane consumption, film deposition rate, and film composition are determined as a function of the methane partial pressure at fixed target current. Argon, silicon, carbon and hydrocarbon ions are detected at the substrate position. The argon and hydrocarbon ions have a narrow energy distribution consistent with the plasma potential. The silicon and carbon ions have a broad energy spread, consistent with that of sputtered neutrals which are post-ionized by the plasma. The film composition (C/Si) varies in the same manner as the arrival ratio of (C+/Si+) ions, but does not correlate well with the arrival ratio of (ΣCHX+/Si+) ions or the methane consumption rate. We conclude that the main source of carbon in Si1−xCx films is the sputtering of C atoms from the Si target surface.
Surface Fermi Level Position of Diamond Treated with Plasma
Authors: Sugino Takashi , Sakamoto Yoshifumi , Furukawa Atsuhiko , shirafuji Junji 
Published: April 2011

ABSTRACTThe surface Fermi level position of undoped epitaxial diamond layers is estimated from contact potential difference between Au reference and diamond measured by Kelvin probe method. The surface Fermi level position of the as-grown layer is located at the energy of 0.75 eV above the valence band edge. O2 plasma treatment leads to an upward shift of the surface Fermi level position to an energy of 1.89 eV from the valence band edge. The surface Fermi level is located at an energy of 0.97 eV above the valence band edge after H2 plasma treatment. Reversible change in the surface Fermi level position is found between O2 and H2plasma treatments. A change in the band bending is observed at the surface of polycrystalline diamond films treated with various ways by X-ray photoclcctron spectroscopy (XPS) analysis. A variation in the current-voltage characteristics of epitaxial and polycrystalline diamonds treated with O2 and H2 plasmas can be qualitatively explained in terms of a change in the band bending due to the shift of the surface Fermi level position.
GaN On 6H-SiC – Structural And Optical Properties
Authors: Wetzel C. , Volm D. , Meyer B. K. , Pressel K. , Nilsson S. , Mokhov E. N. , Baranov P. G. 
Published: April 2011

ABSTRACTRecent progress in the growth of high quality 6H-SiC single crystals has led to an ideal substrate material for GaN epitaxial films. Nearly matching lattice constants of wurzite GaN to 6H-SiC in the hexagonal plane can reduce strain effects at the interface. We employed the sublimation sandwich method to grow single crystal layers at reasonable growth rates with free carrier concentrations of 2×1017 cm-3. Very sharp x-ray diffraction peaks of the GaN (0002) plane are obtained indicating the high quality of this system (Δ(2θ) < 0.1 degrees). These findings are directly reflected in the optical properties. The photoluminescence is dominated by a single sharp exciton line, impurity related donor acceptor transitions are seen with very weak intensities. However, at lower energies the internal luminescence transitions of the 3d transition metal ions Fe and V are observable. The incorporation of Fe is confirmed by electron paramagnetic resonance.
Growth and Characterization of GaN on Si(111)
Authors: Ohtani A. , Stevens K. S. , Beresford R. 
Published: April 2011

ABSTRACTWurtzite GaN films on AlN buffer layers were grown on Si (111) by electron cyclotron resonance microwave plasma assisted MBE (ECR-MBE). High resolution x-ray diffraction studies indicate that the mosaic disorder decreases with increasing growth temperature. The grain size is related to the growth temperature. The best (0002) diffraction peak full width at half maximum was 22 min. for a film 1.7 μm thick. Prominent exciton luminescence is observed at 3.46 eV at 10 K.The plasma I-V characteristics were measured with a Langmuir probe near the growth position. The nitrogen ion density has been extracted from the data, and is a strong function of the N2 flow rate, the microwave power and the aperture size of the ECR source. The crystal quality of AlN is strongly affected by the plasma conditions.
Effect of Aluminum Nitride Buffer Layer Temperature on Gallium Nitride Grown by OMVPE
Authors: Rowland L. B. , Doverspike K. , Gaskill D. K. , Freitas J. A. 
Published: April 2011

ABSTRACTGallium nitride layers were grown by organometallic vapor phase epitaxy on AlN buffer layers deposited in the range of 450–650°C. The GaN growth conditions were kept constant so that changes in film properties were due only to changes in the buffer layer growth temperature. A monotonie improvement in relative crystallinity as measured by double-crystal X-ray diffraction corresponded with a decrease in buffer layer growth temperature. Improvements in GaN electron transport at 300 and 77 K were also observed with decreasing AlN buffer layer temperature. Photoluminescence spectra for the lowest temperatures studied were dominated by sharp excitonic emission, with some broadening of the exciton linewidth observed as the buffer layer growth temperature was increased. The full width at half maximum of the excitonic emission was 2.7 meV for GaN grown on a 450°C buffer layer. These results indicate that minimizing AlN buffer layer temperature results in improvements in GaN film quality.
Electron Spin Resonance Studies of Donors in Bulk and thin Film β3-SiC
Authors: Carlos W. E. , Freitas J. A. , Pazik J. C. , Ivanova L. M. , Altaiskit YU.M. , Zuev V. L. 
Published: April 2011

ABSTRACTWe have investigated the electron spin resonance of donors in bulk and thin film β-SiC at T = 10K to 40K. In both, two donor spectra are resolved; a three line spectrum associated with nitrogen on the carbon site and a broader line of unidentified origin. The observable hyperfine splitting decreases with increasing temperature due to a small valley-orbit splitting, in qualitative agreement with photoluminescence results. The lineshape has a significant lorentzian character even at the lowest temperatures, indicating exchange interactions with residual conduction electrons, possibly from a shallower donor. We find a lower concentration of both donors in the bulk material and a different temperature dependence of the lineshape for the two samples.
Infrared Luminescence from MOCVD Gan
Authors: Leksono M. W. , Oiu C. H. , Melton W. , Pankove J. I. 
Published: April 2011

ABSTRACTAn infrared emission peak at 1.25 eV is observed from a GaN film which exhibits strong yellow luminescence peaking at 2.15 eV. It is most efficient at a temperature of 160 K. The full width at half maximum (FWHM) of the IR peak is 0.17±0.01 eV, which is about 1/3 that of the yellow peak.
Tunable Second-Harmonic Studies of Gan Films Near the Fundamental Bandedge
Authors: Miragliotta Joseph , Bryden Wayne A. , Kistenmacher Thomas J. , Wickenden Dennis K. 
Published: April 2011

ABSTRACTTunable second-harmonic (SH) transmission measurements were performed on a series of GaN films epitaxially deposited onto (OOOl)-oriented sapphire. Analysis of the nonlinear response showed an increase in the second-order nonlinear susceptibility (χ(2)ijk) when the photon energy of the SH field was tuned above the absorption edge in each respective film. Specifically, the magnitude of the χ(2)zxx element in χ(2)ijk reached a maximum of 0.5 × 10-7 e.s.u. just above the the fundamental bandgap with a dispersion similar to the predicted nonlinear response in wide-bandgap cubic zincblende II-VI semiconductors such as ZnSe.
Perturbed -Angular -Correlation Spectroscopy on Indium- and Cadmium- Complexes in Silicon Carbide
Authors: Meier J. , Forkel-Wirth D. , Licht T. , Reislöhner U. , Uhrmacher M. , Witthuhn W. , Collaboration Isolde 
Published: April 2011

ABSTRACTComplex formation at indium and cadmium impurities implanted into samples of 3C-, 4H-and 6H- SiC was investigated by means of Perturbed Angular Correlation (PAC)-Spectroscopy. After annealing at 1600 K up to five different configurations characterized by their specific electric field gradients (EFG(i)) were observed in 6H- SiC, only four complexes in 4H- SiC; in the 3C- modification no complex was observed. All EFG's are axially symmetric and are oriented along the c- axis of the crystal. In a highly nitrogen doped 6H- SiC epi- layer an new EFG was observed. It is tentatively assigned to a close indium- nitrogen pair.
Surface Studies Relevant to the Initial Stages of Diamond Nucleation
Authors: Lannon J. M. , Gold J. S. , Stinespring C. D. 
Published: April 2011

ABSTRACTStudies of diamond heteroepitaxy on silicon indicate that C-C surface species act as nucleation precursors. We have investigated the conversion of the Si(100) 2×1 surface to SiC using C2H4 to obtain an understanding of how C-C species may be formed and to determine the effect of an O-adlayer on enhancing or selecting the reaction channel which leads to these species. Under appropriate conditions, the interaction between C2H4 and the clean silicon surface yields both SiC and C-C species. The presence of an O-adlayer significantly reduces the activity of silicon and enhances the formation of sp2 and sp3 C-C species. These results provide key insights into diamond nucleation conditions in conventional growth processes.
Energies and Atomic Structures of Grain Boundaries in Diamond: Comparison With Grain Boundaries in Silicon
Authors: Kohyama M. , Ichinose H. , Ishida Y. , Nakanose M. 
Published: April 2011

ABSTRACTFairly different features of grain boundaries in diamond from those in Si were experimentally observed in diamond thin films. As the first step in order to understand the fundamental properties of grain boundaries in diamond, the energy and atomic structure of the {122} σ=9 tilt boundary have been calculated for the first time by using the tight-binding electronic theory. The results have been compared with the calculations of the same boundary and the {111} σ=3 boundary in Si. It has been shown that the σ=9 boundary in diamond has a very large interfacial energy caused by the large bond rigidity as compared with the boundaries in Si and the {111}σ=3 boundary in diamond. This point should be related to the observation that the {122}σ =9 boundary is rarely found in diamond thin films.
Fast Recombination of Excess Carrier in 6H-SiC
Authors: Tomashiunas R. , Vanagas E. , Petrauskas M. , Zhindulis A. , Willander M. , Wahab Q. , Bergner H. 
Published: April 2011

ABSTRACTFast carrier recombination phenomena in 6H-SiC has been investigated. Evaluation of carrier recombination in nitrogen doped n-type 6H-SiC grown by the Lely method have been carried out using picosecond photoconductivity, time-resolved photoluminescence and dynamic gratings (DG) techniques. From photoluminescence measurements the hole capture by neutral (nitrogen) donors is discussed. The hole capture times and capture cross sections 820 ps, 2.32 ns and 1.5–10-15cm2, 1.2–10-15cm2, respectively, by each of the inequivalent donor were evaluated. From the photoconductivity measurements the electron lifetimes ∼ 1.5 μs at 300 K and (3.5÷6.5)μs at 125 K were obtained. The ambipolar diffusion coefficient 1.4 cm2.s-1 obtained from dynamic gratings measurements is in good coincidence with the calculated values.
X-Ray Topographic Studies of Defects in PVT 6H-SiC Substrates and Epitaxial 6H-SiC Thin Films
Authors: Wang S. , Dudley M. , Carter C. H. , Kong H. S. 
Published: April 2011

ABSTRACTSynchrotron white beam X-ray topography has been used to characterize defect structures in (0001) 6H-SiC substrates grown by the sublimation physical vapor transport (PVT) technique as well as in 6H-SiC epitaxial thin films grown on these substrates. Defects revealed in 6H-SiC substrates include super screw dislocations and basal plane dislocations. It has been found that back-reflection topographs are particularly suitable for imaging such super screw dislocations as well as basal plane dislocations whenever transmission topography is not applicable. Epitaxial 6H-SiC thin films grown on such (0001) substrates (tilted a few degrees towards the a-axis) were also examined by using surface sensitive grazing Bragg-Laue topography. It has been shown that super screw dislocations were replicated in the epitaxial thin films but no basal plane dislocations were revealed in the thin films. Results from various topographic techniques are discussed.
Solid-State NMR Studies of the Bonding Structure of Diamondlike Amorphous Carbon Films
Authors: Holl Susan M. , Johnson Robert D. , Novotny Vlad. J. , Williams Jeffrey L. , Caley Catherine E. , Hoinkis Mark , Jones Robert E. 
Published: April 2011

ABSTRACTAmorphous carbon films are (a-C:H) of interest because of their useful physical properties. They are extremely hard and chemically inert, resisting degradation by both acids and alkalis. They are insoluble and can be conformably coated onto virtually any substrate. These properties make the films ideal protective coatings on magnetic disks and tools. We have studied several thin (one to two micron) films prepared by plasma enhanced chemical vapor deposition with varying radiofrequency fields strengths to determine structural differences at the atomic level. Several properties of the films, such as hardness and wear rate, are dependent on deposition power. We have found that the sp2/sp3 ratio increases with increasing deposition power. Thus, films that are harder are more “graphitic” and less “diamondlike”. The films studied here contain 11–16 atomic percent hydrogen, most of which is associated with sp3 carbon sites. At least two distinct phases of hydrogens exist. Variable temperature studies reveal that, in contrast to amorphous hydrogenated silicon, proton linewidths in carbon films are temperature dependent, suggesting some molecular motion is present at room temperature.
Application of Desorption Mass Spectrometry to Molecular Beam Epitaxy
Authors: Evans Keith R. 
Published: April 2011

ABSTRACTMolecular beam epitaxy (MBE) is the most powerful crystal growth technique available in terms of the range of structures which can be produced. However, further advances in MBEprocess monitoring and control are required to produce the most demanding structures. Also, process yield, cost, and throughput must be improved for MBE to gain in production worthiness. Because of these issues, there currently is much research activity focusing on the development of advanced in-situ sensors for improved growth parameter monitoring and control. Desorption mass spectrometry (DMS) is an in-situ sensor technique for detecting species leaving the substrate during MBE growth processing. Since in general all surface processes affect desorption rates, and all growth parameters affect surface processes, DMS can be utilized to monitor a variety of MBE growth parameters and phenomena. Theimplementation of simple feedback techniques which link DMS error signals to changes in one or more growth parameters then provides for continuous control of desorption rates. This paper reviews some of the most recent accomplishments in the application of DMS forimproved growth parameter monitoring and control. Additionally, anticipated future directions in the application of DMS to epitaxial growth are discussed.
Materials Issues in Molecular Beam Epitaxy
Authors: Tsao J.Y. 
Published: April 2011

The technology of crystal growth has advanced enormously during the past two decades; among those advances, the development and refinement of molecular beam epitaxy (MBE) has been among the most important. Crystals grown by MBE are more precisely controlled than those grown by any other method, and today form the basis for many of the most advanced device structures in solid-state physics, electronics and optoelectronics.In addition toits numerous device applications, MBE is also an enormously rich and interesting area ofmaterials science in and of itself. In this paper, we discuss a few examples of some of these materials issues, organized according to whether they involve bulk, thin films, orsurfaces [1].
Non-Contact Temperature Measurement with Infrared Interferometry
Authors: Hung Steven C. H. , Dong Haike K. , Tu Charles W. 
Published: April 2011

ABSTRACTWe have successfully utilized the temperature dependence of the refractive indices of various substrates (GaAs and InP) in detecting their temperature variations. The detectionwas accomplished by injecting a beam of HeNe laser (1.15 μm) toward a double-sidepolished substrate. An interference pattern developed among the reflected laser beams, and the actual temperature increment/decrement could be deduced from the interference maxima and minima. The method was first calibrated inside a diffusion furnace from room temperature up to 200ºC, and the detection resolution was found to reach as high as ±0.7ºC. The same measurement setup was later used on the temperature calibration of a substrate heater in a molecular beam epitaxy (MBE) growth chamber, and was finally used to detect surface temperature change during Ar+ laser assisted metalorganic MBE (MOMBE) growth. Because a direct contact is unnecessary and only the relative signal intensity is needed, this low-cost method can be applied to any otherexperiments in a fairly straightforward manner.
Study of Monocrystalline Structure of GaAs/Si Grown by VPE
Authors: Rong Zhang , Youdou Zheng , Yong Yan , Duan Feng , Shanxiang Huang 
Published: April 2011

ABSTRACTA single crystal GaAs/Si heterostructure has been fabricated using the “two step” version of the traditional halogenide VPE technique. The X-ray diffraction spectroscopy, the high resolution electron microscopy observation and the Raman scattering spectroscopy have been used to analyze the structure of the GaAs epitaxial film on Si, while the X-ray photoelectron energy spectroscopy has been used to determine the chemical structure of the GaAs epilayer. The results indicate that the epilayer is a stoichiometric GaAs single crystal film.
Acceptor Concentration Control of p-ZnSe using N2+He Gas Plasma by Molecular Beam Epitaxy
Authors: Kobayashi Masakazu , Yoshikawa Akihiko 
Published: April 2011

ABSTRACTNitrogen and helium mixed gas plasma was used to grow p-ZnSe. Using the mixed gas, the acceptor concentration could be controlled from 6x1016 to 7x1017 cm−3 while films doped using the nitrogen plasma exhibited the acceptor concentration of 3x1017 cm−3. Doping characteristics such as the acceptor concentration and the PL properties depend on the gas mixing ratio and the rf power. Plasma spectroscopy was used to characterize the variety of the species in the plasma. Although the variety of the nitrogen related peaks in the spectrum were not significantly affected by the gas mixing, several peaks (for example 745nm and 825nm) showed intensity variation that was similar to the acceptor concentration variation with respect to the N2 and He gas mixing ratio.