bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cubic Boron Nitride as a New Semiconductor for Optoelectronics: Luminescence Properties and Potentialities
Authors: Era Koh , Mishima Osamu 
Published: March 2011

ABSTRACTIn cubic boron nitride made by high pressure and high temperature technique in our institute, we have found three luminescence bands in the ultraviolet and the short visible region at room temperature by cathode-ray excitation. They are: a band having vibrational structure and ascribable to undoped state of the crystal, a band ascribable to p-type doping and a band ascribable to n-type doping. Discussion is made on differences between the injection luminescence and the cathodoluminescence. Potentialities and difficulties in realizing the potentialities of cBN for optoelectronic applications are discussed.
Boron Phosphide on Silicon for Radiation Detectors
Authors: Lund J. C. , Olschner F. , Ahmed F. , Shah K. S. 
Published: March 2011

ABSTRACTWe report on radiation detectors fabricated from boron phosphide (BP) layers. These devices were fabricated by growing 1 to 10 μm thick layers of BP by chemical vapor deposition (CVD) on (100) oriented n-type silicon substrates. Ohmic contacts were applied to the Si (Au-Sb). Schottky barrier contacts (also Au-Sb) were applied to the BP layer. The devices were tested as radiation detectors and were found to be capable of detecting individual 5.5 MeV alpha particles. With some improvements we hope to fabricate neutron detectors from these devices, making use of the very high cross-section of boron for thermal neutrons.
Synthesis of Metastable Diamond
Authors: Anthony Thomas R. 
Published: March 2011

ABSTRACTDiamond can be grown as an equilibrium phase from a liquid metal solution containing carbon at high pressures and high temperatures. Diamond can also be grown as a metastable phase at subatmospheric pressures and moderate temperatures from hydrocarbon gases in the presence of atomic hydrogen. Atomic hydrogen serves several critical roles in CVD diamond growth, namely: 1) stabilization of the diamond surface, 2) reduction of the size of the critical nucleus, 3) “dissolution” of carbon in the gas, 4) production of carbon solubility minimum, 5) generation of condensable carbon radicals in the gas, 6) abstraction of hydrogen from hydrocarbons attached to surface, 7) production of vacant surface sites, 8) etching of graphite, 9) suppression of polycycic aromatic hydrocarbons. A search for substitutes for atomic hydrogen have been unsuccessful to date but several new processes that do not use atomic hydrogen are currently under study.
Thermodynamics and the CVD of Diamond
Authors: Yarbrough Walter A. 
Published: March 2011

ABSTRACTBulk diamond is unstable relative to bulk graphite except at high pressure and temperature. In spite of this, well crystallized diamond has been grown using numerous CVD methods, most of which have in common the production of atomic hydrogen and hydrocarbon radicals in regimes where solid carbon is expected to be a stable product. Two fundamentally different points of view have emerged in the effort to explain why well crystallized diamond, and not g”reatcphheitde” obry v aittroemouics hcyadrbroogne, nis aot bas erarvtee dh iignh tehre sthea enx dpiearmimoenndt sa. nTd hhee fnicrset dairagmueosn dth iast gkrinapethiictael liys stable with respect to graphite. If diamond formation is kinetically controlled the deposition mechanism is critical and much debate has centered on the mechanism and species involved. Alternatively it is argued that at the growth interface, diamond surfaces are stabilized by termination with hydrogen. If this is correct, and bulk reorganization ignored, then it is shown that a global understanding of the parameters important to the growth of diamond can be obtained without detailed kinetic analyses. Thus it is argued that single crystal diamond films of arbitrarily high purity and perfection are theoretically possible by CVD in spite of the bulk instability of diamond. It is also suggested that general principles exist which might be applied to the growth of other well crystallized metastable phases - notably cubic boron nitride.
Studies of Diamond Growth Mechanisms in a Hot Filament Reactor
Authors: Chu C. Judith , Bai Benjamin J. , D'Evelyn Mark P. , Hauge Robert H. , Margrave John L. 
Published: March 2011

ABSTRACTThe incorporation of methane into low-pressure CVD diamond thin films has been compared to that of acetylene. 13CH4 and 12C2 H2 were used as the hydrocarbon sources in a heated-filament CVD diamond growth process at a total concentration of 0.5% hydrocarbon in 99.5% hydrogen. Results indicated that methane and/or methyl radical is the dominant carbon source for diamond growth in a hot filament reactor under steady state conditions and that acetylene is rapidly hydrogenated to methane. Results also indicated that diamond surface reactions play an important role in determining the relative methane to acetylene ratios.
Adsorption of Hydrocarbon Radicals on the Hydrogenated Diamond Surface
Authors: Pederson Mark R. , Jackson Koblar A. , Pickett Warren E. 
Published: March 2011

ABSTRACTIn order to gain insight into diamond growth, we have calculated equilibrium geometries for several adsorbates on the hydrogenated diamond <111> surface. While the adsorption height of a single methane radical onto a dangling bond is found to be in excellent agreement with the bulk-diamond bond length, the back bonded hydrogens of adjacent adsorbed methyl radicals repel one another. In contrast, adjacent acetlyinic radicals do not repel one another but lead to the introduction of double carbon bonds, misplaced carbon atoms above the active layer and a bond length which is too short in comparison to that of bulk diamond. Our calculations on the acetylene molecule near a dangling bond indicate that the resulting adsorbate bond length is substantially too large and that the carbon atom is unlikely to be stable directly above the surface carbon atom. Of the adsorbates studied, geometrical arguments suggest that the methyl radical is likely to be the most ideal adsorbate.
Optical Properties of II-VI Semiconductor Doped Glass
Authors: Persans P. D. , Tu An , Lewis M. , Driscoll T. , Redwing R. 
Published: March 2011

AbstractWe review structural and optical properties of CdSxSe1−x semiconductor nanoparticles embedded in an insulating glass matrix. Vibrational Raman scattering and x-ray diffraction can be used to determine the composition of the crystallites for all X and sizes. Debye-Scherrer broadening of x-ray diffraction peaks from the crystallites yields an average grain size in the semiconductor crystallites of 60Å for the series studied here. Small angle x-ray scattering reveals that the average particle diameter is close to 120Å. Optical absorption, photoluminescence, and photomodulated absorption spectra are interpreted within a spherical quantum well model. Electron-phonon coupling and size distribution effects on the spectra are also discussed.
Opto-Electronic Properties of μc-Si Grown from SiF4 and H2 by PECVD
Authors: Okada Y. , Campbell I. H. , Fauchet P. M. , Wagner S. 
Published: March 2011

AbstractMicrocrystalline Si was grown from SiF4 and H2 by plasma-enhanced chemical vapor deposition. The films are almost completely crystalline with a crystallite size (determined from Raman spectra) of about 60 Å. The optical absorption and the electrical conductivity of these films were studied. With increasing hydrogen content in the films, the dark conductivity decreases strongly and the activation of the conductivity increases. We explain the conductivity qualitatively in terms of a grain boundary model.
The Role of Hydrogen in Silicon Microcrystallization
Authors: Wagner S. , Wolff S.H. , Gibson J.M. 
Published: March 2011

AbstractWe report and interpret two groups of experiments on the role that hydrogen plays in the formation of silicon microcrystals. We show that the growth of singlecrystal Si by molecular beam epitaxy at 475°C is disrupted by H2, which induces the formation of microcrystals. In crystallization experiments of non-hydrogenated a-Si and of hydrogenated a-Si:H on a hot stage in a transmission electron microscope, hydrogen facilitates the nucleation of crystallites. We explain our observations with a substantial reduction of the grain boundary energy by hydrogen.
Effects of Hydrogen Atoms on Passivation and Growth of Microcrystalline Si
Authors: Ito Toshimichi , Yasumatsu Tatsuro , Watabe Hirokuni , Iwami Motohiro , Hiraki Akio 
Published: March 2011

AbstractEffects of hydrogen atoms bonded to silicon atoms on microcrystalline surfaces in a μc-Si:H and anodized porous silicon have been investigated using infrared spectroscopic technique and a semi-empirical molecular-orbital calculation (AM1 method). Experimental results on thermal stability of the Si-H bonds and oxidation of H-covered Si can be explained consistently in terms of system total energies and heats of formation of various clusters constructed by 13–18 Si and 18–24 H atoms (with an additional 0 atom). Possible role of H on the growth of μ c-Si:H is discussed in relation to stable Si-H bonds.
A Discussion of Electronic Optical Absorption Spectra of Nanocrystalline Silicon thin Films
Authors: Bustarret Etienne , Hachicha M.A. 
Published: March 2011

AbstractBoth fully crystallized nanocrystalline as-deposited silicon layers with an average grain size ranging between 6 and 80 nm and mixed-phase hydrogenated doped and undoped silicon films are studied at room temperature by Photothermal Deflection Spectroscopy (PDS), Transmission Spectroscopy and Spectroscopic Ellipsometry. The differences with regard to similar data obtained on monocrystalline and hydrogenated amorphous silicon are discussed, with an emphasis on the low-energy part of the 0.6-5.6 eV explored range.
Critical Review of Raman Spectroscopy as a Diagnostic Tool for Semiconductor Microcrystals
Authors: Fauchet P.M , Campbell I.H. 
Published: March 2011

AbstractRaman scattering is becoming a widely used tool for the characterization of semiconductor microcrystals due to its sensitivity to crystal sizes below a few hundred angstroms. Through detailed analysis of the first order Raman spectrum it is possible to determine the size and shape of microcrystalline grains. First order spectra must be examined with care however, since they are sensitive to other factors including: stress/strain, surface vibrations, mixed amorphous/microcrystalline phases and intragrain defects. Second order Raman spectra are more sensitive to microcrystalline effects than first order spectra. They offer the potential to measure crystal sizes greater than a few hundred angstroms but much work remains to be done to quantify the size dependence of the second order spectra.
Optoelectronics and Photovoltaic Applications of Microcrystalline Sic
Authors: Hamakawa Y. , Matsumoto Y. , Hirata G. , Okamoto H. 
Published: March 2011

AbstractA review is given of the electrical and optical properties of hydrogenated microcrystalline silicon carbide (μc-SiC:H) films prepared by ECR (Electron Cyclotron Resonance) plasma chemical vapor deposition. The material produced with the ECR plasma technology has a very wide energy gap from 2 to 2.8 eV with good valency electron controllability, e.g., a dark conductivity as high as 10 Scmg− which is more than seven orders of magnitude larger than that of amorphous SiC:H.Employing this material as a wide gap heterojunction window, 15.4% and 12.0% conversion efficiencies have been achieved with the structures of ITO/p type μc-SiC:H/n type poly-Si and p type vc-SiC:H/i type a-Si:H/n type Pc-Si:H heterojunction solar cells, respectively. The successful development of a visible light thin film light emitting diode show the promise of microcrystalline materials for optoelectronic applications.
Dopant Segregation at Polycrystalline Silicon Grain Boundaries in Device Fabrication Processes
Authors: Itoh M. , Aikawa I. , Hirashita N. , Ajioka T. 
Published: March 2011

AbstractThe dopant segregation at the polycrystalline silicon grain boundaries in device fabrication processes has been studied with a new approach using spreading resistance(SR) measurement, SIMS and cross-sectional TEM(XTEM). Phosphorus implanted LPCVD poly-Si films were annealed at 900°C-1000°C in N2 for 30min. Electrically active dopant concentrations obtained from SR measurements are constant in depth within the poly-Si films. On the other hand, the phosphorus concentration measured by SIMS is found to increase with increasing depth and to have linear relationships to reciprocal grain sizes observed by XTEM for all poly-Si films. The linear relationship indicates that the number of segregated phosphorus atoms per unit grain surface area at the grain boundaries is uniform throughout poly-Si films. Both phosphorus concentrations in the grains and at the grain boundaries are evaluated. The heat of segregation of 1.7eV is obtained from the annealing temperature dependence of the segregation ratio. Our results indicate that carrier concentration in the poly-Si film is more sensitive to annealing temperature in device fabrication processes. The carries concentration is determined by kinetics rather than by equilibrium segregation of dopants.
Correlations Between Optical, Electrical, and Structural Properties of In-Situ Phosphorus-Doped Hydrogenated Microcrystalline Silicon - Effects of Rapid Thermal Annealing on Material Properties
Authors: Kotecki David E. , Jeng Shwu J. , Kanicki Jerzy , Parks Christopher C. , Rausch Werner , Seshan Krishna , Tien Jean 
Published: March 2011

AbstractFilms of in-situ phosphorus-doped hydrogenated microcrystalline silicon (n--μc-Si:H) were deposited by plasma enhanced chemical vapor deposition (PECVD) on Si(100) and fused quartz substrates over a range of substrate temperatures (100 - 500°C) and reactant gas dilutions (I - 100% of 1% PH3/SiH4 in H2) while maintaining a constant RF power density (0.1 W-cm−2) and total gas pressure (1 Torr). Some of the films were subjected to a rapid thermal anneal (RTA) at temperatures between 600- 1000°C for a duration of 10 seconds. The μ-Mc-Si:H films were characterized, before and after RTA, in terms of their microstructure, optical band-gap, electrical conductivity, and hydrogen and phosphorus content. The deposition rate was determined to be insensitive to substrate temperature and to decrease with increasing H2 gas dilution indicating that deposition kinetics are dominated by plasma chemistry and are not thermally activated. For pre-annealed films, cross-sectional TEM confirmed the presence of a mixed phase material at all deposition temperatures with gas dilutions ≤10%. The surfaces of thick films (>0.15 μm) were rough, giving them a hazy appearance, while thin μic-Si:H films (<0.15 μm) were smooth and mirror-like. The rough surfaces were correlated with voids and microcracks in the μuc-Si:H films observed by TEM. The optical band-gap of all pre-annealed films was 11.8eV and the electrical conductivity varied between 1 and 20 (Δ-cm)−l. The H content was found to be independent of gas dilution but decreased with increasing substrate temperature; the P content depended on both the gas dilution and substrate temperature, decreasing at high deposition temperatures. RTA was observed to significantly alter film morphology and microstructure, increase electrical conductivity, and decrease the optical band-gap.
Crystal-Axis-Rotation of Laser-Recrystallized Silicon on Insulator
Authors: Sugahara K. , Ippóshi T. , Inoue Y. , Nishimura T. , Akasaka Y. 
Published: March 2011

AbstractThe relation between the seed pitch and defect density of the laserrecrystallized SOI film was investigated. It was found that the defect density of the SOI increases as the seed pitch increases. The dependences of the laser scan speed and laser power on rotation angle of the SOI film were experimentally and numerically investigated. The crystal-axisrotation of the SOI film was considered to be due to the difference of the temperature between the top and bottom surface of the SOI film near the liquid-solid interface. A polysilicon heat sink structure with high thermal conductivity was newly proposed and was found to reduce the rotation in a small angle.
Electrical Properties of Sipos Films Deposited on Crystalline Silicon
Authors: Chuang Tien-Min , Rose Kenneth , Gutmann Ronald J. 
Published: March 2011

AbstractTransport and trapping effects on undoped and phosphorus-doped SIPOS films on n-type and p-type Si have been characterized by C-V-ω, I-V, DLTS and photo-induced microwave reflection techniques. Our C-V and DLTS data on undoped SIPOS indicate that interface traps with a density of 2 × 1012cm−2 eV−1 and a response time between 1 and 10 μsec exist near the midgap of the SIPOS. Photo-induced microwave reflection transient-waveforms show an order of magnitude increase in photoconductivity decay time with doped SIPOS films. Our data shows that trapping effects exist in doped SIPOS and that these traps could reduce the cutoff frequency of SIPOS emitter transistors.
Chemistry and Solid State Physics of Microcrystalline Silicon
Authors: Vepřek Stan 
Published: March 2011

AbstractVarious methods for the preparation of microcrystalline (nanocrystalline) silicon are summarized and compared with respect to the possibility of the control of the materials quality and scaling of the deposition process to large area applications. It is shown that the deposition of a pure microcrystalline material is achieved under conditions close to partial chemical equilibrium. The mechanism of the crystallization during the growth will be briefly discussed.The second part of the paper deals with the physical properties of pure microcrystalline silicon which is free of any amorphous phase detectable by X-ray diffraction, i.e. less than about 1 vol%. Several aspects of electric conductivity, optical absorption and Raman scattering which have been frequently misinterpreted in the literature will be reviewed.
Electrodeposition of 3-D Size-Quantized Cds and CdSe Films
Authors: Hodes G. , Engelhard T. , Albu-Yaron A. , Pettford-Long A. 
Published: March 2011

AbstractCdS and CdSe films electrodeposited from chalcogen-containing non-aqueous electrolytes are shown to possess a nanocrystalline structure and exhibit 3-D quantum size effects. A large variation in optical transmission spectra, due for the most part to this sizequantization, is shown. Photoelectrochemical activity of the as-deposited films is discussed in terms of their nano-structure. Extension of the crystallite size effects to a metalinsulator transition in MoO2 deposited from a similar electrolyte is mentioned.
A Study of the Pressure-Induced Phase Transition in Bulk and Nanocrystalline Cadmium Sulfide
Authors: Zhao Xue-Shu , Schroeder John , Persans Peter D. , Lu Enlian 
Published: March 2011

AbstractWe have used Resonant Raman scattering induced by pressure tuning to study the phase transition and electronic states of bulk and 60±20 Å colloidal microcrystallite CdS. The experimental results show that bulk CdS undergoes a well-defined first order phase transition at 27 kbar and that the intensity of the Raman scattering increases sharply when the level of the intermediate state (bound exciton I2) is close to the photon energy. After the phase transition no Raman scattering and photoluminescence can be observed. However, the phase transition in the colloidal CdS is quite different from the bulk CdS and the complete phase transition occurs above 60 kbar. Both bulk and colloidal CdS reverse to the original wurtzite phase after releasing the pressure.
RF Power Dependence of the Material Properties of PECVD Silicon Dioxide
Authors: Chapple-Sokol J. D. , Tiemey E. , Batey J. 
Published: March 2011

AbstractSilicon dioxide films deposited from the PECVD reaction of silane and nitrous oxide in the presence of helium were studied to determine the effects of RF power on the deposition process. Increased RF power density yielded oxides which were structurally and chemically more homogeneous. The combination of elevated power density with increased silane concentration resulted in the deposition of films of high electrical and physical integrity at high deposition rates.
High Rate Deposition of Hydrogenated Amorphous Silicon Films by ECR Plasma CVD
Authors: Ozaki S. , Akahori T. , Tani T. , Nakayama S. 
Published: March 2011

AbstractA new electron cyclotron resonance (ECR) plasma CVD system has been developed in order to obtain high deposition rates. By using this system, hydrogenated amorphous silicon (a-Si:H) films have been prepared at a deposition rate of 1.0. μ m/min. The utilization efficiency of SiH4 gas is 16% under such conditions. Films prepared at 1.0 μ m/min have high photoconductivity (σ ph) of 10-6 S/cm and low dark conductivity (σ d) of 10-12 S/cm, leading to a high photosensitivity of σ ph/σ d=106. Both high microwave power and high SiH4 gas flow rates are essential to the high rate deposition of sufficiently photosensitive a-Si:H films. Annealing at 300° C improves the photosensitivity up to σ ph/σ d=107.
Formation of Multilayer SiO2- SiOx Heterostructures by Control of Reaction Pathways in Remote PECVD
Authors: Tsu D. V. , Kim S. S. , Theil J. A. , Wang Cheng , Lucovsky G. 
Published: March 2011

AbstractWe have deposited thin films of silicon dioxide, SiO2, and amorphous silicon, a- Si, by remote Plasma-Enhanced Chemical-Vapor Deposition (Remote PECVD), and have extended this process to the deposition of silicon suboxides, SiOx, 0<x<2. Heterostructures, comprised of alternating layers of SiO 2, and SiOx, x∼1, have been deposited by electronically controlling the flow of charged particles from the plasmageneration region into the deposition chamber, without interrupting the flow of process gases. We discuss the electrical properties of these heterojunction structures.
Low Temperature Cleaning of Ge and GaAs Surfaces Using Hydrogen Dissociated with a Remote Noble-Gas Discharge
Authors: Hatitangady S. V , Rudder R. A. , Mantini M. J. , Fountain G. G. , Posthill J. B. , Markunas R. J. 
Published: March 2011

AbstractThe native oxides of Ge and GaAs have long been known to preclude the formation of suitable MIS structures. In situ cleaning of Ge and GaAs surfaces has been achieved at 300–375 °C using a novel technique employing hydrogen that is dissociated using a remote Ar discharge. Such a technique circumvents the problems of cross contamination introduced from a directly excited hydrogen discharge due to erosion of the quartz tube walls by the active hydrogen. Reconstructed surfaces characteristic of clean Ge and GaAs surfaces have been observed with Reflection High Energy Electron Diffraction (RHEED) following such a treatment. Auger and X-ray Photoelectron Spectroscopy (XPS) analyses show that such a treatment removes both oxygen and carbon contamination from the surface. XPS window scans on the Ga-3d and the As-3d peaks show that the treatment is successful in removing oxygen bonded to both Ga and As on the GaAs surface.Following the in situ cleaning, excellent MIS structures on Ge and GaAs have been realized with a novel structure that utilizes an ultra-thin Si interlayer (1.5 nm) between the insulator-oxide and the clean semicondutor surface. The Si interlayer prevents any sub-cutaneous oxidation of the underlying semiconductor while exploiting the advantages of the excellent Si-SiO2 interface. The entire structure is fabricated in a single-chamber remote plasma CVD unit.
Structure and Morphology of Vitreous Chalcogenide Thin Films Obtained by Plasma-Enhanced CVD
Authors: Ribes Michel , Cros Bernard , Peytavin Serge , Camon Henri , Balladore Jean-Louis 
Published: March 2011

AbstractThin films of chalcogenide glasses GeSeywere prepared by PECVD for lithographic applications. Their structure and morphology were characterized by EXAFS and electron microscopy. EXAFS studies enabled comparison of the structures of thin films and those of homologous bulk glasses. Morphology studies by SEM and TEM revealed an heterogeneous structure explained by a phase separation: these glasses consist of microdomains whose size varies with the overall GeSey composition.