bluuebunny/crossref_metadata_2025_split huggingface dataset:
Doping of Diamond by Co-Implantation with Dopant Atoms and Carbon
Authors: Sandhu G. S. , Kao C. T. , Swanson M. L. 
Published: March 2011

ABSTRACTWe have investigated the challenging problem of doping diamonds, by co-implanting boron, nitrogen or phosphorus together with carbon into natural insulating type -a1 diamonds. All the implantations were done at liquid nitrogen temperature and then the samples were rapidly heated to 1100 °C. Unlike the previous attempts to dope diamond by room temperature or high temperature ion implantations, this method is expected to yield a higher doping efficiency for the implanted atoms. We have characterized the implanted diamonds with electrical and electron spin resonance (EPR) measurements. Boron doped samples showed low electrical resistivities and the EPR signal showed a strong dependence on the boron fluence, indicating a high substitutional fraction of boron atoms. The samples in which nitrogen and phosphorus were co-implanted with carbon showed lower resistivities compared with samples implanted with carbon only. Preliminary thermo-emf measurements indicated n-type conduction in these samples.
Electronic Properties of Diamond/Nickel and Diamond/Boron Nitride Interfaces
Authors: Pickett Warren E. , Erwin Steven C. 
Published: March 2011

ABSTRACTWe present self-consistent local density functional calculations of the electronic structure and bonding characteristics of an ideal diamond/Ni (001) interface and an unrelaxed diamond/BN (110) interface. At this stage the small lattice mismatches are not taken into account. Results include predictions of the band line-ups across the interfaces: the Schottky barrier height in the former case and the valence and conduction band discontinuities in the latter case.
Low Temperature Selective Growth Of β -SiC Using SiH2 Cl2/C3H8/HCl/H2 Gas System
Authors: Ohshita Y. 
Published: March 2011

ABSTRACTβ -SiC is grown on a Si(100) substrate by chemical vapor deposition method under reduced pressure using SiH2 Cl2/C3H8/HCl/H2 gas system. The addition of HCI to SiH2 Cl2/C3H8/HCl/H2 gas system makes it possible to obtain a stoichiometric β -SiC film with a mirror surface at low growth temperature of 900°C. Moreover, β -SiC selective growth on Si(100) surface, with no nucleation on SiO2 surface, is achieved. According to the increase of the HCI flow rate, the density of SiC nucleation on SiO2 surface is greatly decreased. Perfect selective β -SiC film is obtained for HCI concentrations greater than 1.2%.
Ohmic Contacts on β-SiC
Authors: Chaudhry M. I. , Berry W. B. , Zeller M. V. 
Published: March 2011

ABSTRACTWe report on ohmic contacts on β-SiC. The contacts were formed using Ni, NiCr, W, Ti, Wsi2 and TiSi2. Contact resistance measurement and Auger Electron Spectroscopy (AES) were used to study annealing effects on contact materials. Auger analysis of Ni-SiC system indicates that during heat treatment, Ni reacts with Si to form silicide. Similar results are found for NiCr-SiC contacts.Minimum contact resistance of tungsten and titanium on SiC is measured to be 6.l×10−3 ohm/cm2 and 7.6×10−3 ohm/cm2, respectively. High temperature annealing deteriorates both contacts although for titanium contacts the resistance increases less dramatically as compared to tungsten contacts. The silicides of tungsten and titanium yield lower contact resistance than metallic W and Ti contacts. The contact resistance for Wsi2 and TiSi2 after heat treatment decreases to 3.0×10−4 ohm/cm2 and 1.1×10−4 ohm/cm2, respectively.
Growth of High-Resistivity Wurtzite and Zincblende Structure Single Crystal Gan by Reactive-Ion Molecular Beam Epitaxy
Authors: Powell R. C. , Tomasch G. A. , Kim Y.-W. , Thornton J. A. , Greene J. E. 
Published: March 2011

ABSTRACTEpitaxial GaN films have been grown at temperatures between 600 and 900 °C by reactive-ion molecular-beam epitaxy. Ga was provided by evaporation from an effusion cell while nitrogen was supplied from a low-energy, single-grid, ion source. The average energy per accelerated N incident at the growing film surface was ≈ 19 eV. Films deposited on Al2O3(0112) and MgO(100)l×l substrates had wurtzite (a-GaN) and metastable zincblende (α-GaN) structures, respectively. The lattice constants were a = 0.3192 nm and c = 0.5196 nm for α;-GaN and a = 0.4531 nm for β -GaN. The room-temperature optical bandgap Eg of zincblende GaN, 3.30 eV, was found to be 0.11 eV lower than that of the hexagonal polymorph α-GaN. All films were n-type with electron carrier concentrations which decreased from 4×1018 to 8×1013 cm−3 with increasing incident N2+/Ga flux ratios between 0.63 and 3.9. Resistivities <106Ω-cm were achieved.
Structural Defects in GaN Epilayers Grown by Gas Source Molecular Beam Epitaxy
Authors: Sitar Z. , Paisley M. J. , Yan B. , Davis R. F. 
Published: March 2011

ABSTRACTSingle crystal cubic or hexagonal GaN thin films have been grown on various substrates, using a modified gas source MBE technique. A standard effusion cell was employed for the evaporation of gallium. A compact electron cyclotron resonance plasma source was used to activate the nitrogen prior to deposition. The films were examined by transmission electron microscopy. The major defects in the wurtzite GaN were double positioning boundaries, inversion domain boundaries, and dislocations. The zinc-blende GaN showed microtwins, stacking faults, and dislocations. The connection between the observed structural defects and the poor electrical properties of GaN is noted.
Vibrational Spectroscopy of Boron Nitride at High Temperatures and Pressures
Authors: Exarhos Gregory Y. , Hess Nancy J. 
Published: March 2011

ABSTRACTRaman scattering measurements are used to distinguish between amorphous and crystalline phases in sputter deposited boron nitride coatings and bulk materials. Changes in vibrational line frequency and linewidth can be attributed to differences in particle size or inherent strain which can be quantified from pressure-dependent measurements of the bulk material. The response of the Raman-allowed E2g modes (hexagonal phase) to temperature is described by a forced dampeg harmonic oscillator model from which the intra- and interplanar lattice thermal expansion can be estimated.
The Preparation of III-V Semiconductors in Aqueous Solution
Authors: Cumberbatch Toby J. , Putnis Andrew 
Published: March 2011

AbstractIndium arsenide colloids have been prepared by passing arsine through an aqueous solution of the metal nitrate. Similar experiments with gallium solutions produced an extremely fine precipitate which has been tentatively identified as amorphous gallium arsenide. Attempts to precipitate aluminium arsenide from aqueous solutions or mixed organic solvent systems were unsuccessful. The materials were characterised by transmission electron microscopy, X-ray powder diffraction and and optical absorption spectroscopy.
Fractal-Like Structures Present in Hydrogenated Amorphous and Microcrystalline Silicon
Authors: Geerts M.J. , van Oort R.C. , van den Heuvel J.C. 
Published: March 2011

AbstractIn hydrogenated amorphous silicon NMR studies indicate a twophase structural inhomogenity. Hydrogenated microcrystalline films consist of small crystals with a typical size of 100 Å, embedded in an amorphous web. A hydrogen rf plasma is able to etch both type of films, but with different etch rates. The more crystalline parts of a film are etched more slowly, which makes hydrogen plasma etching a technique that can reveal structural inhomogenities and differences in structural disorder as present, both in amorphous and in microcrystalline silicon films.Amorphous and microcrystalline films were etched and fractal-like structures were visible when using a SEM at a magnification of 20000 times. In microcrystalline films the fractals form a closed network. The number and typical size of the fractals present in amorphous films can be influenced by the conditions during the deposition.
Picosecond Photomodulation Study of Nanocrystalline Hydrogenated Silicon
Authors: Wraback M. , Chen Lingrong , Tauc J. , Vardeny Z. 
Published: March 2011

AbstractWe have extended our photomodulation studies of nc-Si:H to the picosecond time domain. We measured the decays of photoinduced reflectivity with 100fs temporal resolution as a function of light intensity. Comparison with the data obtained on a-Si:H and c-Si indicates that ultrafast trapping and recombination processes are mainly the properties of the amorphous phase. It has also been observed that nc-Si:H is unstable under high illumination.
Raman Scattering from Microcrystalline Films: Considerations of Composite Structures with Different Optical Absorption Properties
Authors: Nemanich R.J. , Buehler E.C. , LeGrice Y.M. , Shroder R.E. , Parsons G.N. , Wang C. , Lucovsky G. , Boyce J.B. 
Published: March 2011

AbstractRaman scattering measurements are used to characterize the components of microcrystalline Si and carbon films. A model is described which addresses the properties of Raman scattering from composites of materials of different optical absorption. The analysis shows that the observed spectra are dependent on both the percentage of the components and on the domain size of the more highly absorbing domains. Carbon films produced by different enhanced CVD techniques show both sp2 (graphite) and sp3 (diamond) regions. Silicon films prepared by excimer laser exposure of hydrogenated a-Si and by magnetron sputtering showed features due to both microcrystalline and amorphous regions. The experimental results reflect the length scales of the domains and vibrational excitations.
Role of Surface and Growth-Zone Reactions in the Formation Process of µc-Si:H
Authors: Matsuda A. , Goto T. 
Published: March 2011

AbstractThe role of the surface reaction is discussed in the formation process of µc-Si:H in comparison to that of a-Si:H. It is suggested that the responsible radicals for the formation of µc-Si:H are SiH3 as same in the case of a-Si:H depositions. On the top film-growing surface, a lot of H atoms reach the surface during the course of the μc-Si:H growth giving rise to the change in the surface condition, i. e. the loss probability of SiH3 radicals is increased. At the same time, a full H-coverage of the surface is expected which enhances the surface diffusion of SiH3 radicals, leading to the appearance of a gc nucleus. Moreover, it is speculated that the reaction in the growth zone is not necessary for the nucleation process in µc-Si:H.
The Effect of Hydrogen on the Structure of Amorphous and Microcrystalline Sic Prepared by the Polymer Route
Authors: Chu C-J , Ting S-J. , Bobonneau F. , Mackenzie J.D. 
Published: March 2011

AbstractAmorphous SiC:H thin films have been deposited on different substrates using metal-organic polymer solutions. The structure of the amorphous phase has been proposed as the rings of Si and C atoms with various sizes. Microcrystalline phase can be produced when fired at temperatures higher than 1000°C. 13C MAS-NMR shows the evidence of the C=C-double bonds. ESR results show the major defects in this material are C-dangling bonds. As predict, defects can be decreased by heat treatment in H2 atmosphere.
Selective Deposition of N+ Doped MC-SI:H:F by Rf Plasma Cvd on Si and S1O2 Substrates
Authors: Baert K. , Deschepper P. , Pattyn H. , Nijs J. , Mertens R. 
Published: March 2011

Abstractμc-Si:H:F can be deposited by if plasma-CVD of fluorinated gas sources like SiF4 and SiH2F2, mixed with H2 and/or SiH4. However, this growth process is usually not selective: the layers are deposited on SiO2 as well as on Si substrates. In this paper, selective growth from SiF4 + SiH4 is reported. N+ Si layers were deposited on <100> Si and poly-Si with a conductivity up to 300 resp. 100 S/cm. The selective growth process was applied for Source and Drain regions of poly-Si thin film transistors on insulating substrate.
Development of the Very thin Microcrystalline N-Layer and its Application to the Stacked Solar Cell
Authors: Nakabeppu F. , Ishimura T. , Kumagai K. , Fukui K. 
Published: March 2011

AbstractIn order to improve the efficiency of the amorphous silicon stacked solar cells, we have developed the preparation method of highly conductive very thin microcrystalline silicon n-layers. We have found that the addition of a small amount of Ar gas to deposition gases is effective to make microcrystallite size small. The obtained thin films were characterized by conductivity measurement, R-HEED observation and TEM observation.This newly developed thin microcrystalline n-layers have been applied to the stacked solar cells. Increase of Jsc by 5-6% has been achieved because of the reduction of light absorption loss in n-layer without decrease of Voc and FF.
Microcrystalline Silicon Films Produced by RF Magnetron Sputtering and the Effect of Diffrent Ambients on their Conductivity
Authors: Berjee Ratnabali , Bandyopadhyay A. K. , Sharma S. N. , Patabyal A. K. , Barua A.K. 
Published: March 2011

AbstractResults on characterisation of undoped, μc-Si:H films prepared by rf magnetron sputtering technique are presented. Highly conducting films (10−3 Δ−cm−1) were obtained at fairly low rf power density (l.2W/cm2). Critical parameters for obtaining microcrystalline phase were identified. The effect of humid ambient on film properties was looked into.
Structural and Electrical Characterization of CdSe Thin Films
Authors: Hatalis Miltiadis K. , Lin Fuyu , Westcott Michael R. 
Published: March 2011

AbstractThe structural and electrical properties of thin films of undoped and indium-doped cadmium selenide deposited on glass substrates have been investigated. The as-deposited films were found to be microcrystalline with grain size less than 10 nm. Grain growth occurred upon annealing. Enhanced grain growth was observed in the indium doped films. Transmission electron microscopy of in-situ annealed films revealed the formation of large single crystal areas having cubic structure with <111> as the dominant orientation. The resistivity and the effective electron mobility of polycrystalline cadmium selenide films were investigated as function of annealing conditions and device channel length. Reduction of the electrical resistivity and increase of the electron mobility was observed in devices with channel lengths less than 25μm.
Directional Deposition of Silicon Oxide by a Plasma Enhanced TEOS Process
Authors: Hsieh J. J. , Ibbotson D. E. , Mucha J. A. , Flamm D. L. 
Published: March 2011

AbstractWe have characterized the step coverage and film quality of (tetraethoxysilane) TEOS-based silicon oxides which are directionally deposited on horizontal surfaces of trench features under oxygen-lean conditions in a high frequency (14 MHz) discharge. The film thickness on the sidewalls depends most strongly on the O2 :TEOS feed ratio. Water uptake after ambient exposure was used as a measure of film quality and the amount of water absorbed in the film correlated well with changes in the refractive index and stress. Oxide quality on horizontal surfaces could be improved by decreasing the TEOS feed or increasing the discharge power, but the sidewall oxide quality could not be improved by these methods. Small NF3 additions to the discharge markedly improved sidewall quality, altered the angle between the sidewall and the bottom of trench features from 90° to ˜115° (tapered profile) and increased the deposition rate, while preserving the directionality of deposition.
Polyhydride Bonding Groups in PECVD Amorphous Si Thin Films.
Authors: Davidson B. N. , Parsons G. N. , Wang C. , Lucovsky G. 
Published: March 2011

AbstractIn glow discharge deposition (GD) of a-Si:H alloys, the concentration of electronically-active defects increases as the incorporation of bonded hydrogen in polymerized dihydride groups, (SiH2)n increases. Since the fraction of dihydride groups increases strongly with decreasing substrate temperature (Ts), the incorporation of these bonding groups can only effectively be reduced by restricting Ts to about 230°C or higher. We have found that a-Si:H films produced by remote Plasma Enhanced Chemical Vapor Deposition (remote PECVD) are qualitatively different than the GD films in the following ways: 1) the amount of bonded hydrogen for Ts > 100°C is less by about a factor of two; and 2) the fraction of polyhydride bonding is also significantly less than the monohydride fraction for Ts > 100°C. We develop a statistical model that provides a basis for translating any process-dependent representation of data for the polyhydride fraction into a universally-obeyed scaling relationship in which the independent variable is [H]. The agreement between the statistical model and the experimental data, replotted as a function of [H], supports our observation that the fraction of polyhydride bonding is not determined simply by Ts, but is a function of the particular reaction pathways in the deposition process chemistry.
Diamond Forming Discharges
Authors: Bachmann Peter K. , Lydtin Hans 
Published: March 2011

AbstractMethods to prepare diamond thin films by means plasma chemical vapor deposition are reviewed. The various techniques available to date are compared with respect to their deposition rates, deposition area, quality and homogeneity of the material produced, and their specific advantages and drawbacks. The deposition rates of both thermally induced and plasma induced CVD methods correlate well with the gas temperature in the reaction zone supporting the hypothesis that the large quantities of diamond precursor species necessary for high deposition rates are formed in a hot spot of the deposition system.
In-Situ SubStrate Temperature Measurement During a-Sin Plasma CVD from N2 Rotational Temperature
Authors: Ishihara Shin-Ichiro , Otsuka Akira , Nagata Seiichi 
Published: March 2011

AbstractRotational temperature (Tr) of nitrogen molecule, equivalent to the gas temperature (Tg), was used for monitoring silicon nitride (SiN) surface temperature during rf glow discharge processing. SiN film characteristics such as deposition rate and etching rate for mixture of hydro-fluoric acid (HF) and ammonium fluoride : (NH4F) were dependent on Tr near the substrate. The Tr increased not only with substrate temperature setting (To) but also with gas mixing ratio of H2/(H2+N2) due to improvement of thermal conductance from heater to substrate in the process chamber.
Magnetoklasticity in Rare-Earth Kultiiayers and Films
Authors: Erwin R.W. , Rhyne J.J. , Borchers J. , Salamon M.B. , Du R. , Flynn C.P. 
Published: March 2011

ABSTRACTThe magnetic structure has been measured with neutron scattering and SQUID magnetometry for a number of epitaxial multilayers and films of the magnetic rare-earths dysprosium and erbium grown with non-magnetic yttrium. In almost all cases the first order ferromagnetic phase transitions are suppressed, although the Néel temperatures are within 5% of the bulk values. The observed critical fields are explained by including epitaxial constraints with the bulk theory of magnetoelasticity.
Neutron Scattering Methods for Materials Science
Authors: Pynn Roger , Lujan Manuel 
Published: March 2011

ABSTRACTThis article describes some of the neutron scattering techniques which can be used to probe structures of materials on length scales which range from less than 1 Å to 1 μm. The intent is to remove the veils of secrecy and mystery which have apparently prevented the wide application of these techniques to problems in materials science.
Neutron Depolarization by Flux Latrices in High-TC Materials
Authors: Pickart S. J. , Nunes A. C. , Crow M. L. , Fu Bo , McGuire T. R. , Shinde S. , Shivashankar S. A. 
Published: March 2011

ABSTRACTWe have recently reported[l] neutron depolarization measurements on an YBa2Cu3O7−δ composition exhibiting a transition from a low temperature state which caused depolarization (P=0.76+−.02) to one at high temperatures (T=55K) where depolarization was absent. Since this temperature is well below the measured superconducting transition at 86K, we speculated that the transition was a dynamic one corresponding to flux lattice melting[2] or to formation of a glassy state[3]. We have now extended these depolarization measurements to two specimens of Bi2.2Sr1.7CaCu2O8+δ' prepared and characterized[4] at IBM, which showed superconducting transitions at 80K with weak tails extending to 110K. The two samples have critical current densities, as determined by the Bean expression[5], that differ by 50%.
In-Beam Small-Angle Scattering Studies of Phase Separation in Ni-Ti Single Crystals
Authors: Cerri Alberto , Schoenfeld Bernd , Kostorz Gernot , Wright Albert F. 
Published: March 2011

ABSTRACTPhase separation of quenched supersaturated Ni-(9.5-12.0)at.% Ti single crystals was followed by small-angle neutron scattering during in-beam aging at 773, 813 and 853 K. With the incident beam along <110>, scattering maxima in <100> directions were observed from the earliest stages of decomposition. While the results obtained at 773 K may be compatible with the general features of spinodal decomposition, a two-phase model with homogeneous precipitation in a depleted matrix is more appropriate at 813 and 853 K. Though scaling may be shown to hold, the aging kinetics is considerably slower than expected, which is related to a stabilizing effect of elastic coherency stresses.
Vibrational Spectra for Hydrogenated Amorphous Semiconductors
Authors: Kamitakahara W. A. , Biswas R. , Bouchard A. M. , Gompf F. , Suck J. B. 
Published: March 2011

ABSTRACTHydrogen vibration spectra have been measured by neutron scattering for several amorphous semiconductor materials, including a-Ge:H and a-SiC:H samples containing about 10 at. % H. The data for a-Ge:H are compared in detail with the results of realistic computer simulations.
Comparison of Neutron Elastic and Inelastic Scattering from Fused Quartz, Cab-O-Sil and Aerogel
Authors: Root John H. , Buyers William J. L. , Page John H. , Schaefer Dale W. , Brinker C. J. 
Published: March 2011

ABSTRACTNeutron scattering experiments have been performed to study the structure and dynamics of three preparations of silica: a dense glass (fused quartz), a flame-hydrolyzed aggregate (Cab-O-Sil, grade M5) and a polymeric aerogel. The experiments were performed on the three materials at temperatures selected from 300, 77 and 4.2 K. Neutron inelastic scattering was measured at Q = 2.5, 2.9 and 4.0 Å−1.The elastic scattering indicates a systematic decrease in positional correlations on progressing from fused quartz through Cab-O-Sil to aerogel. The inelastic scattering was analyzed with the Buchenau model [1] to obtain the sample, Q and temperature dependences of the density of states, g(v). In the aerogel g(v) increases with temperature at frequencies greater than 1.5 THz and is enhanced at Q = 2.5 Å−1. Thus a complete explanation of the inelastic scattering from aerogels must account for multiphonon processes, local antiphase motions and anharmonic effects.
Characterization of Molecular Network of Thermosets Using Neutron Scattering
Authors: Wu Wen-Li 
Published: March 2011

ABSTRACTNeutron scattering measurements were conducted to investigate the conformation of the molecular networks in epoxies. Emphasis was placed on the changes in the scattering intensity resulting from curing. Experimental results on homopolymerized epoxy as well as a theoretical interpretation of the results are presented.
Thermal Diffuse Scattering in Neutron Time-of-Flight Powder Patterns
Authors: Radler Michael J. 
Published: March 2011

ABSTRACTInelastic scattering from lattice phonons contributes a significant fraction of the observed Bragg intensity in time of flight neutron powder patterns of transition metal monoxides at elevated temperatures. Ignoring this thermal diffuse scattering (TDS) leads to errors in the site occupations of defects present in these materials. The intensity from one phonon TDS has been calculated as a function of time-of-flight and used to correct the measured intensities. The effect of this correction on the results of Rietveld profile refinement is discussed.