bluuebunny/crossref_metadata_2025_split huggingface dataset:
Charge Carrier Relaxation after Subbandgap Excitation in Doped a-Si:H
Authors: Werner A. , Kunst M. 
Published: March 2011

AbstractCharge carrier dynamics in doped and undoped a-Si:H after subbandgap excitation at 1064 nm was followed by transient photoconductivity experiments. The kind of optical transitions induced by 1064 nm light is strongly dependent on the position of the Fermi-level. This allows the seperation of excess electron and excess hole kinetics as in n-doped samples mainly mobile electrons and in moderately p-doped samples mainly free holes are generated by 1064 nm light. From comparison of the photoconductivity after 532 nm and 1064 nm excitation it is inferred that the rate controlling step for the electron decay is the availability of free holes.
Low-Carbon Boron Carbidestproduced by CVD
Authors: Campbell A. N. , Mullendore A. W. , Tallant D. R. , Wood C. 
Published: March 2011

ABSTRACTBoron carbides with low C contents were produced from BC13 and CCl4 by chemical vapor deposition at temperatures of 1020–1500°C. The deposits were found to be between B13C2 and B13 C (8.3 to 13.3 at %C) in composition by means of Auger electron spectroscopy. Raman spectroscopy demonstrates that the specimens contain very little free carbon. Further, disordering of C in the chains and icosahedra of the rhombohedral boron carbide structure for C contents of less than 20 at.% is indicated by the Raman results. Singlephase rhombohedral boron carbides with C contents as low as 12.5 at.% (≈B7C) have been produced. The most B-rich specimens, containing 8.3 at.% (B11 C) or less C, were phase separated. At least one of the phases in the phase separated specimens is tetragonal. The electrical conductivity and Hall mobility of the B11C specimen are reported.
A Comparison of Calculated and Experimental Hrtem Images for Twinned Boron Carbide
Authors: Miller Mark L. , Mackinnon Ian D. R. 
Published: March 2011

ABSTRACTHigh resolution TEM images of boron carbide (B13C2) have been recorded and compared with images calculated using the multislice method as implemented by M. A. O'Keefe in the SHRLI programs. Images calculated for the [010] zone, using machine parameters for the JEOL 2000FX AEM operating at 200 keV, indicate that for the structure model of Will et al., the optimum defocus image can be interpreted such that white spots correspond to B12 icosahedra for thin specimens and to low density channels through the structure adjacent to the direct inter-icosahedral bonds for specimens of intermediate thickness (-40 > t > -100 nm). With this information, and from the symmetry observed in the TEM images, it is likely that the (101) twin plane passes through the center of icosahedron located at the origin. This model was tested using the method of periodic continuation. Resulting images compare favorably with experimental images, thus supporting the structural model. The introduction of a (101) twin plane through the origin creates distortions to the icosahedral linkages as well as to the intra-icosahedral bonding. This increases the inequivalence of adjacent icosahedral sites along the twin plane, and thereby increases the likelihood of bipolaron hopping.
Heteroepitaxial Growth of Antiphase-Boundary Free Cubic Sic(100) Single Crystals on Si(100)
Authors: Shibahara Kentaro , Nishino Shigehiro , Matsunami Hiroyuki 
Published: March 2011

ABSTRACTCubic SiC was grown on Si substrates by a combination of carbonization and consecutive chemical vapor deposition. Grown layers on the (100) and (111) substrates were single crystalline cubic SiC. Those on the (110) and (211) were poly-crystalline. A model for the mechanism of carbonization was proposed as a result of these observations. Based on this model, the origin of antiphase boundaries were made clear, and antiphase boundaries were expected to be eliminated by controlling atomic steps of the Si surface. In fact, antiphase boundaries were eliminated by introduction of off orientation of Si(lO0) substrates. The relationship between generation of antiphase boundaries and off orientation of the surface was investigated by using spherically polished Si(100) substrates. Off orientation towards (011) was found to be effective for elimination of antiphase boundaries. Off orientation except for towards (011) resulted in generation of antiphase boundaries.
Optical, Vibrational and Surface Properties of SiC
Authors: Choyke W. J. 
Published: March 2011

ABSTRACTA short historical introduction concentrates on key experimental and theoretical developments prior to the mid-seventies which form the basis of our present understanding of the semiconducting and optical properties of the polytypes of SiC. Selected research of the last decade is reviewed. Finally, we discuss our on-going surface and defect studies in both epitaxial single crystal films of 3C SiC and other hexagonal SiC polytypes.
Lattice Vibrations and Defect-Induced Vibrational Properties in Cubic SiC
Authors: Lin-Chung P. J. 
Published: March 2011

ABSTRACTA theoretical study of both the bulk phonon dispersion relations in cubic SiC and the vibrational properties induced by native defects is presented. The Keating Hamiltonian is used for the quadratic potential energy of the system, and the supercell approach is employed to treat the defect problem. The defect complexes considered are antisite defects, divacancy defects, and three different types of carbon di-interstitial defects.
Growth, Doping, Device Development and Characterization of CVD Beta-SiC Epilayers on Si(100) and Alpha-SiC(0001)
Authors: Kong H. , Kim H. J. , Edmond J. A. , Palmour J. W. , Ryu J. , Carter C. H. , Glass J. T. , Davis R. F. 
Published: March 2011

ABSTRACTMonocrystalline β-SiC films have been chemically vapor deposited on Si(100) and c-SiC(0001) at 1660K-1823K and 0.1 MPa using SiH4 and C2H4 carried in H2. Films grown directly on Si(100) contained substantial concentrations of dislocations, stacking faults and antiphase boundaries (APB); those on α-SiC(0001) contained double positioning boundaries. Both the APBs and the double positioning boundaries were eliminated by using off-axis orientations of the respective substrates. Films produced on Si(100) have also been doped during growth and via ion implantation with B or Al (p-type) or P or N (n-type) at LN, room and elevated temperatures. Results from the former procedure showed the ionized dopant/total dopant concentration ratios for N, P, B and Al to be 0.1, 0.2, 0.002 and 0.01, respectively. The solubility limits of N, P and B at 1660K were determined to be ∼ 2E20, 1E18 and 8E18 cm−3, respectively; that of Al exceeds 2E19 cm−3. High temperature ion implantation coupled with dynamic and post annealing resulted in a markedly reduced defect concentration relative to that observed in similar research at the lower temperatures. Schottky diodes, p-n junctions, and MOSFET devices have been fabricated. The p-n junctions have the characteristics of insulators containing free carriers and deep level traps. The MOSFETs show very good I-V characteristics up to 673K, but have not been optimized.
Residual Donors in P-SiC Films
Authors: Carlos W. E. , Moorea W. J. , Siebenmann P. G. , Freitas J. A. , Kaplan R. , Bishop S. G. , Nordquist P. E. R. , Kong M. , Davis R. F. 
Published: March 2011

ABSTRACTElectron Spin Resonance (ESR), temperature dependent Hall effect measurements and photoluminesence (PL) are used to examine the assumption that the residual donor in β-SiC films is nitrogen. At low temperatures the ESR has a three line isotropic spectrum which is characteristic of a central hyperfine interaction with nitrogen. The temperature dependence of the intensity of the nitrogen ESR signal correlates with the concentration of un-ionized donors measured by the Hall effect. Donor-Acceptor pair PL spectra are used to establish that the binding energy of the dominant donor in the films is the same as the nitrogen donor observed in Lely-grown samples. Neither PL nor ESR provide any evidence for the presence of a shallower donor.
Thermally Activated Reactions of Titanium Thin Films with (100) 3C-SiC Substrates
Authors: Bellina J. J. , Zeller M. V. 
Published: March 2011

ABSTRACTThe reaction of thin Ti films deposited, in situ, onto (100) 3C-SiC has been studied by Auger Electron Spectroscopy, and Low Energy Electron Diffraction. The effects of reaction temperature and SiC surface condition were investigated as part of a program to obtain a high temperature electrical contact for this wide band gap semiconductor.The results indicate that the interface reaction is dominated by the formation of TiC in SiC, and the liberation of Si which diffuses to the surface. The amount of liberated Si depended on the relative amounts of free surface C and of deposited Ti. In the presence of excess carbon, the reaction of Ti with SiC was suppressed and a (TiC + C) surface layer formed which was stable after 500 hours at 800°C.
Effects of the Subsequent Ion Irradiation on the Formation Process of β-SiC from Si-C Mixtures Fabricated on Si by Ion Implantation
Authors: Kimura Tadamasa , Yamaguchi Hiroyuki , Yugo Shigemi , Adachi Yoshio 
Published: March 2011

ABSTRACTThe β-SiC formation process through post-implantation annealing of Si-C mixtures fabricated on Si by C-ion implantation at room temperature is studied by means of infrared absorption spectroscopy. It is shown that the formation of B-SiC from the Si-C mixtures is greatly enhanced by the subsequent irradiation of other energetic ions prior to the thermal annealing. The continuous amorphization of the Si-C mixed layers is considered to be the dominant cause for the enhancement of the B-SiC formation. The activation energy of the β-SiC formation process which is 5.3 eV without irradiation is reduced to 4.0 eV by the irradiation of 150 keV, 1 × 1017/cm2 Ar ions.
Icosahedral Boron-Rich Solids as Refractory Semiconductors
Authors: Emin David 
Published: March 2011

ABSTRACTIcosahedral boron-rich solids are refractory materials composed of twelve-atom boron-rich icosahedral units with strong intericosahedral linkages. These distinctive structures admit unusual electronic and thermal transport properties. Here the distinctive (three-center) bonding which underlies these materials is first described. Then it is shown how insulators, semiconductors and highly degenerate (metal-like) materials emerge from the same basic structure with appropriate substitutions.The electronic transport of the boron carbides is then addressed. The boron carbides are degenerate p-type semiconductors in which the charge carriers are diamagnetically aligned pairs of electrons which hop between icosahedra. Uniquely, this thermally activated hopping conductivity increases with increasing hydrostatic pressure. However, the Seebeck coefficient (thermoelectric power) is uncharacteristic of a degenerate semiconductor. Namely, the Seebeck coefficient is typically both large and an increasing function of temperature. In addition, despite the hardness and refractory character of these materials, their thermal conductivities can be surprisingly low with a glass-like temperature dependence. These features are manifestations of the distinctive structure and bonding of these solids. In fact, this novel mix of properties makes the boron carbides exceptionally good very-high-temperature p-type thermoelectric materials.Icosahedral boron-rich solids have additional potential as high temperature semiconductors. In particular, the wide-gap icosahedral boronrich pnictides, B12P2 and B12As2, may be doped to form wide-gap refractory semiconductors. For example, replacement of the group V element with either a group VI or a group IV element is expected to yield n-type and ptype material, respectively.
Lanthanide Refractory Semiconductors Based on the Th3P4 Structure
Authors: Gschneidner K. A. , Nakahara J. F. , Beaudry B. J. , Takeshita T. , Laboratory Ames 
Published: March 2011

ABSTRACTThe phase relationships and the important structural, electrical and thermal properties of the R3X4-R2X3 (where R = lanthanides and X = S, Se and Te) phases having the Th3P4 -type structure are reviewed. The room temperature electrical resistivity and Seebeck coefficient of these materials are independent of R and only slightly dependent on X, but critically dependent on the X:R ratio. The long term stability of these phases is also reviewed. Although these materials have good thermoelectric properties there are some problems which need to be solved before these phases can be utilized in thermoelectric devices. These problems include long term stability, higher than desirable thermal conductivities, and low electron mobilities.
Synthesis, Magnetic, Electrical and Mössbauer Investigations on Complex Semiconductors
Authors: Steinfink Hugo , Swinnea John Steven 
Published: March 2011

ABSTRACTThe system Ba-Fe-S contains a phase Ba1+xFe2S4 whose structure consists of infinite chains of FeS4 edge sharing tetrahedra with Fe-Fe distances of 2.7Å. The chains are 6 Å apart and Ba2+ fills the space between the chains. Each value of x designates a distinct phase and such structures have been labeled “infinitely adaptive.” The Ba1+xFe2S4 compounds are anisotropic semiconductors. The room temperature electrical conductivity for the x = 0 and x = 0.086 phases changes by nearly 6 orders of magnitude as increasing x populates the conduction band. The preparation of these materials requires very careful control of sulfur vapor pressure in closed ampules at elevated temperatures. A similar effect is observed in rare earth sulfides with the Th3P4 structure. Intrinsic La2S3 and BaLa2S4 are predicted to be high resistivity semiconductors. As the composition changes to a stoichiometry such as Ba0.8La2.2S4 the behavior becomes semi-metallic. Control of the sulfur vapor pressure will be a critical parameter for designing physical parameters into these compounds.
Role of Oxygen in Rare Earth Chalcogenide Semiconductors
Authors: Vaughan Cheryl M. , White William B. 
Published: March 2011

ABSTRACTOxygen uptake by the rare earth chalcogenides takes place through a series of ordered compounds. At high oxygen concentrations the distinct and nearly stoichiometric oxychalcogenides, Ln202X (X = S, Se, Te) appear. For the chalcogenides of the larger rare earths there appears an ordered oxygen-containing beta structure, Ln10X14OxX1-x (X = S, Se). The vibrational spectrum of the trigonal oxysulfide structure contains four infrared and four Raman bands (2 A2u + 2 Eu + 2 Alg + 2 Eg). Band wavenumbers across the La to Lu series vary linearly with unit cell volume. The Raman bands are sharp indicating a high degree of order in the intermediate compounds. The Raman bands of the beta structure are remarkably sharp indicating that this compound also has a highly ordered structure. Known data plus synthesis data are combined to form not-impossible phase diagrams for the larger rare earth sulfide systems. The effect of oxygen in both series of compounds is to produce small wavenumber shifts rather than high wavenumber oxygen impurity bands.
Atomic Interactions in a Boron-Rich Carbon-Containing Icosahedron: Para-Carborane
Authors: Beckel C. L. , Obarski G. E. , Fuka M. Z. , Fritts J. D. 
Published: March 2011

ABSTRACTBoron carbides contain carbon atoms as substituents for boron in icosahedra. The B-C interaction is different in icosahedra from that in other geometric forms. Para-carborane, P-C2B10H12, offers an excellent system for the study of structure and interactions in boron-rich, carbon-containing icosahedra; its structure is well-characterized experimentally, and the infrared and Raman spectra have been observed and are relatively simple. Here we present an analysis of p-carborane by classical force field methods supplemented by quantum mechanical calculations. Complexity in the model cluster is introduced step-by-step beginning with B12 (Ih symmetry). The principal interaction constants extracted through interpretation of p-C2B10H12 spectra are kCB −2.0 × 105 dyne/cm, kBB (intrapentagon) −1.3 × 105 dyne/cm, and kBB (interpentagon) −1.55 × 105 dyne/cm.
Temperature Measurements in Atmospheric Spraying Plasmas Jets : Gas and Particles in Flight
Authors: Fauchais P. , Coudert J. F. , Vardelle M. , Vardelle A. 
Published: March 2011

ABSTRACTSpectroscopic temperature measurements of spraying plasma jets (produced by D.C. arcs) are studied (equilibrium conditions, influence of the surrounding environment of plasma jets at 1 atm). For solid particles in flight in these jets are presented the measurement methods of surface temperature, particle vapors densities and excitation temperatures. The “limitation of these measurements are discussed and examples are given.
In-Situ Monitoring of Electrical Parameters for Dry Etching
Authors: F J. Ignacio Ulacia , McVittie James P. 
Published: March 2011

ABSTRACTIn this paper, external electrical measurements and a circuit model are used to obtain indirectly the plasma potential, electron density, ion current density, and sheath thickness. In a revised and extended circuit model, each element describes a current-transport mechanism. Each mechanism is described by an analytical expression in terms of previously specified plasma parameters. The model is applicable in capacitive discharges with equal-area electrodes, and it can be expanded to consider other systems. To verify its applicability, electrical measurements of voltage, current and phase angle in an SF6 : O2 discharge are used to calculate the plasma impedance. Electrical plasma measurements yield time-averaged values for the impedance; the values obtained for each device reflect this dependency. After the calculation of each electrical device, SPICE 3.7a simulations separated the individual contribution of current transport by each mechanisms and validated the assumptions. The plasma parameters obtained by this technique agree well with a Langmuir-probe measurement, solutions of the Boltzmann transport equation, and data published in the literature.
Theoretical Prediction of the Effect of Coil Configuration on Gas Mixing in an Inductively Coupled Plasma Torch
Authors: Mckelliget John W. , El-Kaddah Nagy 
Published: March 2011

ABSTRACTA mathematical model for the analysis and design of inductively coupled plasma torches Is presented. The model is based upon a solution of the electromagnetic vector potential equation and is capable of predicting the two-dimensional velocity, temperature, and electromagnetic fields as well as the reaction kinetics inside the torch for any axi-symmetric coil configuration. The model is used to study the effect of coil geometry on the thermal decomposition of silicon tetrachloride to silicon. The coil geometry Is found to affect both the temperature field and the flow field and to have a significant effect on the reaction kinetics in the torch. It is demonstrated that through fundamental changes in the coil design It is possible to control the location of the reaction zone and to prevent silicon deposition on the wall of the reactor.
Growth and Characterization of Epitaxial GaAs Deposited by Plasma-Enhanced Metal-Organic Chemical Vapor Deposition
Authors: Huelsman A. D. , Yoon E. , Reif R. 
Published: March 2011

ABSTRACTEpitaxial GaAs films have been deposited using a Plasma-Enhanced Metal Organic Chemical Vapor Deposition (PE-MOCVD) technique. This technique uses an RF discharge to dissociate arsine and hydrogen upstream from the substrate. The plasma increases the partial pressure of arsenic above the substrate and improves the growth and quality of GaAs films grown at low teyperature and with low arsine flow rates. We have used photoluminescence, Hall measurements, dislocation etches, and transmission electron microscopy (TEM) to study the properties of films grown with and without plasma. enhancement under a variety of reactor conditions. Specular epitaxial layers of n-GaAs were grown with and without plastua at, very low pressures (2 – 3 Torr) on semiinsulating GaAs substrates. Layers grown both with and without the plasma showed good mobility and photoluminescence at deposition temperatures of 650°C. At lower deposition temperatures the films deposited with the plasma were better than those deposited without the plasma. A KOH-NaOH eutectic etch revealed a better structural quality in films deposited with plasma at low arsine partial pressure.
A Study of Titanium Silicide Polycide Etching
Authors: Bobbio S. M. , Ho Y. S. , Lopez T. 
Published: March 2011

ABSTRACTThe reactive ion etching of polycide films (TiSi2 over polysilicon) is discussed. Experimental conditions which lead to anisotropy and the identification of certain contamination problems as well as their solution are presented.
X-Ray Photoemission Study of Silicon Nitride-GaAs Interfaces in Relation with GaAs Mesfet Passivation
Authors: Alnot Patrick , Olivier J. , Wyczisk F. , Peray J. F. , Joubart R. 
Published: March 2011

ABSTRACTWe have studied the influence of different GaAs surface treatments on the chemical composition and electrical behavior of the Si 3 N4 -GaAs interface, where Si 3 N4 was plasma enhanced chemical vapor deposited (PECVD) onto the treated GaAs(100) substrate. The chemistry of the resulting interface has been studied by X-ray photoelectron spectroscopy (XPS). It has been demonstrated that the chemical composition of the Si 3 N4-GaAs interface is drastically dependent on GaAs surface pretreatment and r.f. plasma excitation frequency. Output-input powers characteristics have been measured on chemically treated planar MESFET after Si3N4. passivation.
Measurement of Plasma Etch-Induced Damage to Silicon Beneath Si0 2 Layer: Effective Range of Plasma Etch Damage Through Si0 2
Authors: Smith W. Lee , Connick I-Wen Huang 
Published: March 2011

ABSTRACTThe ability to pattern VLSI wafers by plasma etching through SiO2 without causing structural damage and chemical contamination to the underlying silicon material is today highly desired. Examples are the plasma etching of metal/silicon contact holes and the fabrication of charge injection windows for EEPROM devices. Damage to underlying silicon, which may adversely affect contact resistance, oxide breakdown or charge retention properties, occurs as the oxide is reduced in thickness below a certain penetration depth (Dox). Dox is the effective projected range of damage-producing particles in Si0 2, and is a function of the distributions of energy, mass, etc., of the plasma constituents. In this paper we describe the use of thermal wave modulated reflectance in conjunction with a simple tapered-oxide film structure to measure the depth of penetration of etch-induced damage through SiO 2. Results on the dependence of the penetration depth on RIE self-bias voltage and other observations of etch-induced surface modifications are reported.
The Mathematical Modelling of Transport Phenomena in Non-Transferred Plasma Systems: Accomplishments and Unresolved Problems
Authors: Dilawari A. H. , Szekely J. 
Published: March 2011

ABSTRACTAn overview is presented of transport phenomena in non-transferred plasma arc systems. It has been shown that while the modelling of these systems involves the standard application of computational fluid mechanics techniques, numerous pitfalls may be encountered in practice. A detailed discussion of these is presented, with emphasis on the torch inlet conditions, the effect of swirl, the temperature dependence of the system properties and the laminar-turbulent transition in the system. A critical comparison is presented with experimental measurements, and the necessary future work is also outlined.