bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Formation of Helical Dislocations in Silicon Substrates During Epitaxial Deposition of β- SiC
Authors: Aindow M. , Cheng T. T. , Pirouz P. 
Published: March 2011

ABSTRACTA study is presented of the dislocation content of (001) Si substrates after the formation of thin epitaxial “buffer layers” of beta-SiC by the pyrolysis of propane. Helical dislocations are observed running parallel to the interface and extending for many microns. The dislocation helices emanate from the substrate, have 1/2<110> Burgers vectors which are inclined to the interface, and do not lie on the {111} glide planes. This is consistent with the extension of dislocations in the substrate by climb. The extended segments are subsequently pinned and further climb gives rise to the observed helical configuration. These climb effects are presumably due to an excess of vacancies which are produced when Si interstitials migrate to the deposit in order to form SiC.
Some Observations on the Electrical Characterization of the Heteroepitaxially Grown Cubic SiC
Authors: Molnar B. , Kelner G. 
Published: March 2011

ABSTRACTThis paper re-examines the electrical characterization of thin layers of cubic SiC, grown on (100) Si substrates. The resistivity and Hall coefficient for undoped SiC layers were measured between 10 K and 500 K. Electron spin resonance (ESR) and secondary ion mass spectrometry (SIMS) were used to identify and determine the nitrogen concentrations, which were higher than 1017/cm3. In all the samples examined the Hall measurements indicated impurity band conduction. Therefore, the temperature dependence of the resistivity has been used to derive an activation energy el. The value of el found to be in the range of 0.032–0.025 eV. The observed decrease in activation energy has been correlated with an increase in nitrogen concentration. The presence of substantial nitrogen leads to impurity band conduction and it is the most likely reason for the conflicting values reported for the dominant donor ionization energy by Hall and PL measurements.
Simple Graphitic Network Models of “Diamondlike” Carbon
Authors: Tamor Michael A. , Wu Ching-Hsong 
Published: March 2011

ABSTRACTSeveral highly disordered forms of carbon are termed “diamondlike” by virtue of their extreme hardness and significant optical gap. However, it is quite tempting to extend the analogy further and attribute these “diamondlike” properties to a high degree of local diamond order. Although an “amorphous diamond” character has been inferred from the optical properties in the 0-10 eV range, and the position of the π + σ plasmon peak in the electron energy loss spectrum, there is no direct evidence for such diamond order. However, there is a considerable body of work showing that DLC embodies a considerable degree of graphitic order which determines the optical gap and Raman spectrum. In order to determine to what extent a clearly non-diamond structure can exhibit specific “diamondlike” properties, we examine a simple structure derived from graphite. This “defected graphite” (DG) construct presumes an underlying graphitic structure which is insulating due to the strong localization of π -electrons by randomly distributed non-aromatic defects. Using specific defects suggested by experiment, the DG model reproduces a quite surprising array of observed properties of both hydrogenated and hydrogen-free “diamondlike” carbon.
Microstructural and Optical Characterization of GaN Films Grown by PECVD on (0001) Sapphire Substrates
Authors: Humphreys T. P. , Sukow C. A. , Nemanich R. J. , Posthill J. B. , Rudder R. A. , Hattangady S. V. , Markunas R. J. 
Published: March 2011

ABSTRACTEpitaxial GaN films have been grown by plasma-enhanced chemical vapor deposition (PECVD). The growth procedure utilizes a He gas discharge combined with the down-stream introduction of trimethylgallium (TMGa) and nitrogen. Both cubic [1111 and wurtzitic [0001] GaN epitaxial films have been achieved on (0001) sapphire substrates. Differences in substrate growth temperatures are believed to account for the different observed phases. A comparative study pertaining to the microstructural, optical and electrical properties of the α-GaN and β-GaN heteroepitaxial films is presented. Also reported for the first time is the Raman spectroscopy data for cubic GaN.
Thermal and Ion Bean Induced Reactions in Ni on BP
Authors: Kobayashi Naoto , Kumashiro Yukinobu , Revesz Peter , Li Jian , Mayer James W. 
Published: March 2011

ABSTRACTThe solid phase reactions of Ni thin films with refractory wide bandgap semiconductor BP(100) were investigated both in the thermal process and the ion beam induced process with RBS, AES, XRD and XPS. In the thermal reaction process, reactions of Ni thin films with BP started around 350°C. Transient metastable phases were observed between 400°C and 450°C. The formation of the fully reacted crystalline phase with the mixture of NiB and Ni3P was observed at 450°C. At elevated temperatures above 600°C, mixture of phases with less Ni content was found to be formed. For the ion beam induced process inhomogeneous reaction was observed at LN2 and the reaction at RT showed an amorphous phase with the same composition as the first thermal phase. The reaction at 200°C induced the same crystalline phase as the first thermal phase. The reacted layer thickness as a function of the ion beam fluence between RT and 300°C increased linearly with the fluence by showing the thermal dependence with an activation energy of Ea=O.31±O, O6eV above 100°C.
The Role of Polarity on the Stability of Graphitic Compounds
Authors: Wentzcovitch Renata M. , Continenza Alessandra , Freeman A. J. 
Published: March 2011

ABSTRACTThere is an old puzzle associated with the series of compounds formed by first row elements, C, BN, and BeO: similar to the other members of the family of octet semiconductors, these compounds exist in dense phases like diamond and zincblende, or hexagonal diamond (lonsdaleite) and wurtzite; however, whereas C and BN also exist in low density graphitic phases, BeO does not.
ZnGeP2: A Wide Bandgap Chalcopyrite Structure Semiconductor for Nonlinear Optical Applications
Authors: Xing G. C. , Bachmann K. J. , Posthill J. B. , Timmons M. L. 
Published: March 2011

ABSTRACTIn this paper we report the growth and characterization of wide bandgap chalcopyrite structure semiconductor ZnGeP2 epitaxial layers by open tube MOCVD and ZnGeP2 single crystals by high-pressure vapor transport (HPVT). The electrical and optical properties of these crystals have been investigated by Hall measurements, absorption spectroscopy, photoconductivity and photoluminescence spectroscopy. The onset of the absorption edge for HPVT ZnGeP2 at 1.99 eV is in accord with the pseudodirect bandgap of this material. Both the meltgrown crystals and epitaxial layers show extended band tailing in the transparency range of ZnGeP2 depending on the growth conditions. Recently we have shown that epitaxial ZnGeP2 films can be grown with excellent surface morphology by MOCVD on (111) GaP substrates. These films should be suitable for phase matched second harmonic generation utilizing CO laser radiation in thick film heterostructures.
Microwave CVD of Diamond Using Methanol-Rare Gas Mixtures
Authors: Buck M. , chuang T. J. , Kaufman J. H , Seki H. 
Published: March 2011

ABSTRACTThe deposition of diamond from a reactive vapor phase has been dominated by the use of very dilute gas mixtures of hydrocarbon molecules, usually methane, in hydrogen. Recently there have been reports using nitrogen and oxygen containing simple organics such as amines and alcohols which seem promising. The role of atoms other than hydrogen is still not very clear. There is need for more experimental data to further our understanding in this regard. Here we give a preliminary report on our investigation of deposition from methanol-rare gas mixtures using a small microwave reactor. An important result is that good diamond can be deposited from methanol without addition of hydrogen gas and the quality of the crystallites can be influenced by Ar in the plasma.
Fabrication and Characterization Studies of Semiconductor-Impregnated Porous Vycor Glass
Authors: Huber C. A. , Huber T. E. , Salzberg A. P. , Perez J. A. 
Published: March 2011

AbstractPorous Vycor glass has been impregnated with semiconductors by pressure forcing the nonwetting semiconductor melt into the interconnected pores. Dense semiconductor mesh-like microstructures with a characteristic size of 50 Å can be fabricated by this technique. Measurements are reported which show the composites are suitable for both optical and transport studies, particularly those addressing quantum confinement of carriers and unusual electrical transport phenomena in this new class of materials.
Synthesis, Structural and Optical Characterization of II-VI Semiconductors Included in Sodalite-Type Hosts
Authors: Moran K. L. , Harrison W. T. A. , Gier T. E. , Dougall J. E. Mac , Stucky G. D. 
Published: March 2011

AbstractSolid-state chemistry has been used to control both the size and the interconnection distance of small II-VI semiconductor moeities incorporated in zeolitic hosts with the sodalite-type structure. Structural characterization was carried out using X-ray Rietveld powder methods, and optical properties of these materials were also measured. These novel materials show quantum superlattice effects as evidenced by blue shifts in their optical absorption spectra.
Particle-Size Distribution of CdSe Quantum Dots Determined by Photoluminescence Spectroscopy
Authors: Prabhakar E.N. , Huber C.A. , Heiman D. 
Published: March 2011

AbstractParticle-size distribution effects on the energy levels of semiconductor quantum dots are investigated. By examining the low temperature photoluminescence spectra of microcrystals of the binary semiconductor CdSe embedded in a glass matrix, the distribution of energy levels due to three-dimensional confinement is determined. Calculations of the electron-hole pair ground state energy provide a relation between confinement energy and particle diameter. This allows conversion of the photoluminescence lineshape directly into a distribution of particle radii and facilitates analysis of the observed properties of the material. With extension to other systems the technique can become a valuable tool in the study of semiconductor microparticle composites.
Thermal Annealing of Amorphous CoMnNiO Film on Oxidized Si Substrate
Authors: Hui Tan , Dong Qin , Mingde Tao , Chenglu Lin , Shichang Zou 
Published: March 2011

AbstractAmorphous CoMnNiO film is doposited on oxidized Si substrate by RF sputtering equipment. Structure relaxation occurs in the amorphous CoMnNiO film when it is annealed below 550°C. Annealed in the range from 600°C to 1000°C, the amorphous film is converted into the polycrystal. After annealing in rich oxygen atmosphere, the amorphous film is transformed into spinel solid solution with stable structure and good electrical properties. The electrical conductivity will be reduced due to formation of low valence oxides when annealed without oxygen. As annealing temperature is higher than 1000°C, some spinel solid solutions will be resolved into low valence oxides CoO and NiO, reducing the conductivity of the CoMnNiO film.
Microcrystal Si Films Prepared by Remote Plasma CVD
Authors: Kim Sung Chul , Hwang Jung Tae , Lee Seung Kyu , Jung Chang Young , Soe Sung Moo , Koh Sung Ok , Chung Kwan Soo , Jang Jin 
Published: March 2011

AbstractThe effects of deposition temperature, rf power and hydrogen dilution ratio on the growth, structure and transport of p-type microcrystal(μc-) Si films deposited by remote plasma CVD have been investigated. While low substrate temperature and low rf power yield small grain sizes, high temperature and high rf power tend to supress the growth of grains. The etching of Si by hydrogen radicals plays an important role to grow μc-Si, but excess etching supresses the growth of crystallites. We obtained 400 A of grain size and 3.5 S/cm of room temperature conductivity for p-type μ-Si.
Fast-Pulse Excimer-Laser-Induced Processes in a-Si:H
Authors: Winer K. , Bachrach R.Z. , Johnson R.I. , Ready S.E. , Anderson G.B. , Boyce J.B. 
Published: March 2011

AbstractThe effects of fast-pulse excimer laser annealing of a-Si:H were investigated by measurements of electronic transport properties and impurity concentration depth profiles as a function of incident laser energy density. The dc dark conductivity of laser-annealed, highly-doped a-Si:H increases by a factor of ∼350 above a sharp laser energy density threshold whose magnitude increases with decreasing impurity concentration and which correlates with the onset of hydrogen evolution from and crystallization of the near-surface layer. The similarities between the preparation and properties of laser-crystallized a-Si:H and pc-Si:H are discussed.
Formation of Microcrystalline Silicon film by RMS Process
Authors: Wang Cheng , Parsons G.N. , Buehler E.C. , Nemanich R.J. , Lucovsky G. 
Published: March 2011

AbstractWe have deposited microcrystalline, gc-Si, silicon films by using RF reactive magnetron sputtering (RMS) at high substrate temperatures, Ts > 500°C, and at a relatively low partial pressure of hydrogen, PH = 0.40 mTorr, and at low Ts ∼200- 300°C, but with a higher PH > 2 mTorr. We have detected μc-crystallinity by Raman scattering and transmission electron microscopy. We discuss differences in the growth mechanisms for formation of μc-Si under these two deposition conditions.
Growth of Microcrystalline Silicon in Ultrathin Layers
Authors: Wu Y.-J. , Persans P. D. , Abeles B. , Wang S.-L. 
Published: March 2011

AbstractWe report recent studies of the crystallization of ultrathin (< 10 nm ) amorphous silicon layers clad by silicon dioxide. We observe changes in Raman scattering spectra which indicate that nanocrystalline silicon layers formed by crystallization of amorphous silicon continue to evolve structurally with further annealing. There is evidence for significant strain in crystallized material.
Optical Properties of Microcrystalline Silicon
Authors: Ingels Martin , Stutzmann Martin , Zollner Stefan 
Published: March 2011

AbstractOptical properties of undoped, microcrystalline silicon are investigated by photothermal deflection spectroscopy, spectroscopic ellipsometry and Raman scattering. Samples are prepared by recrystallization of hydrogenated amorphous silicon in the temperature range 680 – 900°C. The increase of grain sizes with increasing annealing temperature and the disappearance of amorphous tissue lead to noticeable changes in the observed spectra. It is argued that much of the pertinent structural information of μc-Si can be obtained by a suitable combination of optical measurements alone.
Suppression of Acceptor Deactivation in Siucon by Disordered Surface Regions
Authors: Srikanth K , Ashok S. 
Published: March 2011

AbstractPermeation of atomic hydrogen in p-type Si damaged with ion implantation or deposited with polycrystalline or amorphous Si has been studied. Following ion implantation or film deposition, atomic hydrogen was introduced by low energy H ion implantation or from an electron cyclotron resonance (ECR) plasma. Spreading resistance profiles indicate that deactivation of acceptor dopant boron atoms by atomic hydrogen is drastically reduced in silicon wafers with any of the above disordered surface layers, and secondary ion mass spectroscopy (SIMS) traces this reduction to the suppression of hydrogen movement into the crystalline Si substrate. Trapping of hydrogen or formation of molecular hydrogen at defect sites in the surface disordered regions apparently is responsible for this phenomenon.
Phonon States in Sic Small Particles
Authors: Sasaki Y. , Horie C. , Nishina Y. 
Published: March 2011

AbstractSize dependence of optical phonon frequencies and that of phonon dampings of SiC small particles have been studied by analysing their Raman data. The particle size ranges from 30 nm to 1000 nm. Decrease in the TO-phonon frequency as well as the LT-splitting (the splitting between the LO- and TO-phonon) with decrease in the particle size are much larger than that expected from the spatial correlation model or that from the phonon confinement model. The phonon damping for the small particle consists of the usual temperature-dependent term and an excess damping term, which is independent of temperature. These results suggest that the scattering of the phonon at the particle surface plays a major role in determining the phonon states of the small particle. Our experimental data suggest that the surface phonon-polariton mode at the interface between the crystallites plays a minor role in the Raman spectrum of particles consisting of a number of crystallites.
Nonlinear Optical Properties of Structured Nanoparticle Composites
Authors: Birnboim Meyer H. , Ma Wei Ping 
Published: March 2011

AbstractThe effective nonlinear susceptibility X( 3 ) for a composite that consists of a dilute suspension of structured nanoparticles that utilizes the surface mediated plasmon resonance can be enhanced by orders of magnitude compared to the intrinsic X(3) for a film of the same neat material. Here we report calculations for various multilayer spherical nanoparticle models in a host dielectric: i) polymeric core and metallic shell, ii) semiconductor core and metallic shell, iii) metallic core, polymeric shell and metallic second shell, and iv) metallic core, semiconductor shell and metallic second shell. The polymer is polydiacetylene, FDA, the semiconductor is Si, the metal is Ag, and the host is water, a GaAs2 glass or Si. Enhancements as great as 104 can be obtained in both x(3) and the figure of merit with no degradation in the intrinsic speed of the nonlinearity. The choice of geometrical parameters and of component materials permit tailoring of the wavelength dependence and bandwidth characteristics of the nonlinear response. However, fabrication of these structured nanoparticle suspensions remians the key challenge.
The Effect of Hydrogen on the Structure and Electrical and Optical Properties of Silicon-Germanium Alloys
Authors: Fortmann C.M. , Albright D.E. , Campbell I.H. , Fauchet P.M. 
Published: March 2011

AbstractThe transport properties of intrinsic micro-crystalline and amorphous SiGe films are investigated. In the amorphous system it is found that the electron lifetime is relatively independent of band gag while the electron mobility of a-Ge:H is a factor of ten less than that of a-Si:H. Micro-crystalline silicon films have greater excess photo-conductivity as compared to a-Si:H predominantly due to longer effective lifetimes. Films containing micro-crystalline silicon in a matrix of a-SiGe:H have been prepared and are found to have comparatively poor transport.
Raman Studies of Microstructural Changes in Amorphous Silicon-Boron Alloys Due to Annealing
Authors: Yang G. , Bai P. , Wu Y.-J , Tong B. Y. , Wong S. K. , Du J. , Hill I. 
Published: March 2011

AbstractCrystallization of amorphous Sil−x.Bx alloy films by annealing is studied. Amorphous Sil−xBx. alloy films with composition of boron x ranging from 0.01 to 0.5 are deposited on Si substrates at a temperature of 480° in a low pressure chemical vapor deposition (LPCVD) system. Three films with the boron contents, 1%, 7% and 45%, are used in this study. The films are annealed in a nitrogen ambient for 30 minutes at temperatures between 600°C and 900°C. Raman spectra of the silicon vibrational mode serve as a indicator for the microstructure of the Sil−xBx, alloy films. Quantitative estimates of the volume fraction of the crystalline silicon component in respect to the amorphous silicon component in the films are calculated based on the silicon TO mode. The results show that while for the film with the boron content of 1% crystallization occurs at the annealing temperature of 500°C, the annealing temperature of 7000C is required to observe crystallization in the films with the boron contents of 7% and 45%. As the annealing temperature increases, the volume fraction of the crystalline component increases. For a given annealing temperature, the rate of crystallization depends inversely on the boron content in the films.
Characteristics of μc-Si:H for Si Heterojunction Bipolar Transistors
Authors: Fujioka H. , Ito M. , Takasaki K. 
Published: March 2011

AbstractTo improve the thermal stability of the Si heterojunction bipolar transistors (HBTs), we studied the effect of carbon and fluorine doping on μc-Si:H characteristics. We found that carbon doping suppresses crystalline growth and increases the hydrogen concentration in the film, and that fluorine atoms are more thermally stable than hydrogen atoms. We confirmed that carbon or fluorine doping is promising for use with the μc-Si:H HBT.
Electronic and Structural Characterization of the Near Surface Layer and the Bulk in νc-Si:H Prepared with Hydrogen dilution
Authors: Aljishi Samer , Jin Shu , Stutzmann Martin , Ley Lothar 
Published: March 2011

AbstractThe near surface layer and the bulk of νc-Si:H prepared with hydrogen dilution are investigated by Raman, optical absorption, and total yield photoelectron spectroscopies. The results show that for low hydrogen dilution ratios, microcrystallites appear in the bulk while the growing surface layer remains amorphous, indicating that microcrystallite formation takes place primarily in the sub-surface layer. At high hydrogen dilution ratios, microcrystallites are detected at both the bulk and the near surface layer. The defect density and hydrogen bonding configurations at various hydrogen dilution levels are presented.
Preparation of Crystalline Si thin Films by Spontaneous Chemical Deposition
Authors: Komiya Tohru , Kamo Akira , Kujirai Hiroshi , Shimizut Isamu , Hanna Jun-Ichi 
Published: March 2011

AbstractThe novel technique for the preparation of crystalline Si thin films termed “Spontaneous Chemical Deposition” has been proposed, in which silane decomposes spontaneously by gas phase reactions with fluorine at reduced pressure. The technique provided us the crystalline films in a wide range of the preparation conditions by a choice of the external parameters for the reactions. The films exhibited unique characteristics in the chemical structure and the optical and electrical properties, different from the conventional uc-Si:H thin films by the silane plasma processes.The technique have been successfully applied for the homoepitaxial growth of Si thin films.
The Graphitization of Amorphous Hydrogenated Carbon Films During Thermal Annealing
Authors: Lin Sam Shuhan , Chen Shuguang , Mo Dang 
Published: March 2011

AbstractEffects of thermal annealing on the properties of amorphous hydrogenated carbon films have been studied with spectroscopic ellipsometry, electrical conductivity, and infrared and Raman spectroscopy. The results show that not only the optical and electrical properties, but also the infrared and Raman spectra, change significantly after annealing above 400°C. We suggest that thermal annealing makes amorphous hydrogenated carbon films more graphite-like, and the observed changes in the microstructure cause the changes in the optical and electrical properties.