bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microstuctural Evolution and Substrate Selectivity in Pecvd μc-Si
Authors: Parsons Gregory N. , Boland John J. , Tsang James C. 
Published: March 2011

ABSTRACTWe discuss a process for selective area deposition of microcrystalline silicon (μc-Si) using plasma enhanced chemical vapor deposition at low substrate temperature (<300°C) using time modulated silane flow in a hydrogen plasma. We discuss selectivity and deposition rate on a variety of substrates with process conditions important for manufacturing applications, and show a distinct microstructural evolution in the initial nucleation layers using Raman spectroscopy that correlates with the transition from selective to non-selective growth. Atomic hydrogen discriminates between different degrees of bond strain in the nucleii formed on different substrates, and can increase the crystallinity fraction in films deposited at low temperatures by modifying the kinetics of bulk-like bond formation.
Crystallinity Analysis of Amorphous-Crystalline Mixed Phase Silicon films Using Exafs Method
Authors: Wakagi Masatoshi , Kaneko Toshiki , Ogata Kiyoshi , Nakano Asao 
Published: March 2011

ABSTRACTThe crystalline phase fraction (Xc) of amorphous-crystalline mixed phase Si films prepared by thermal annealing of a-Si:H films and by plasma CVD and chemical annealing methods was investigated by the EXAFS method. The EXAFS spectra of these films were represented by linear-combination of a-Si:H and c-Si EXAFS spectra. The values of Xc were analyzed by least-square curve fitting. The crystallinity was also analyzed by a Raman scattering method measured from both sides of the films. Then, the Xc values analyzed by the Raman method were calibrated by the EXAFS analysis results.
Modeling of Boron Diffusion in Polysilicon-On-Silicon Layers
Authors: Sultan Akif , Batra Shubneesh , Lobo Melvyn , Park Keunhyung , Banerjee Sanjay 
Published: March 2011

ABSTRACTIn the present study we have modeled the diffusion of boron in single crystal silicon from an ion-implanted polysilicon film deposited on a single crystal silicon substrate. Modeling has been done for both BF2 and boron implants in the polysilicon layer. A new phenomenological model for a diffusivity has been implemented in the PEPPER simulation program using an effective concentration-dependent diffusivity approach. The effective diffusivities of boron in single crystal silicon have been extracted using Boltzmann-Matano analysis. The modeling has been implemented for a wide range of furnace anneal conditions (800°C to 950°C, from 30 min. to 6 hours), and implant conditions (BF2 doses varied from 5×1015 to 2×10'16 cm-2 at 70 keV, boron dose of 5×1015 cm-2 at 20 keV).
Raman Studies of Heavily Doped Polycrystalline Si Films Prepared by Excimer-Laser-Annealing of Doped a-Si:H
Authors: Savage M. E. , JaYamaha U. , Compaan A. , Aydinli A. , Shen Dashen 
Published: March 2011

ABSTRACTExtremely heavily doped polycrystalline silicon films were prepared by multiple-pulse XeCl excimer laser annealing of hydrogenated amorphous silicon films. The as-grown films used here included five types: intrinsic, boron-doped, phosphorous-doped, and carbon alloyed with and without boron doping. Raman studies reveal that the annealed films prepared from the boron or phosphorous doped a-Si:H have high carrier activation and display the interference lineshape (Breit-Wigner-Fano) of the discrete phonons (Si-Si and Si-B modes) interacting with the continuum of the single particle electronic Raman scattering. The Raman lineshapes indicate concentrations of ∼1 × 1021 cm3. This is confirmed by dark conductivities exceeding 100 S/cm in the annealed boron-doped and phosphorous-doped layers.
Si Film Growth by Supercooling of a Molten Si Alloy Film
Authors: Wallace R. L. , Yi J. , Anderson W. A. 
Published: March 2011

ABSTRACTA method is described for the deposition of large-grain polysilicon films at low substrate temperatures. This technique uses precipitation from a thin molten prelayer of Si-Au or Si-Au which is supersaturated with Si from a DC magnetron sputter gun. Typical growth temperatures are 600° C for the Si-Al layer, and 500° C for the Si-Au layer. Growth rates of 6 μm/hr have been achieved, though higher rates seem possible. Films of 20 μm thickness and grain size up to several hundred μm have been grown on SiO2 and sheet Mo substrates using Au and Al as the “solvent” metals. The proposed model for film growth was confirmed by cross-section EDS studies of the film/substrate interface. Film crystallinity was confirmed by etching studies, X-ray diffraction, and selected area diffraction. Preferential nucleation has been achieved using a patterned suicide forming metal (Cr,Ni) on RuO2, coated oxidized wafer. A loss mechanism of the solvent metal during growth was observed.
Polysilicon thin Films and Devices Produced by Low-Temperature (600°C) Furnace Crystallisation of Hydrogenated Amorphous Silicon (a-Si:H)
Authors: Dyer T. E. , Marshall J. M. , Pickin W. , Hepburn A. R. , Davffis J. F. 
Published: March 2011

ABSTRACTIn this work, we report on the electronic properties of polysilicon thin films and devices realised via furnace crystallisation of undoped a-Si: H. The onset of crystallisation, degree of amorphisation and average grain size are determined by UV reflectivity and electron microscopy. Grain size is found to increase with decreasing a-Si:H substrate temperature, and a maximum areal grain size of 0.4μm2 is obtained. Optical absorption, DC conductivity and transient photoconductivity measurements are employed to examine carrier transport mechanisms. We observe a Meyer-Neldel relationship between the DC conductivity prefactor σ0 and activation energy Eσ. A plasma hydrogenation treatment of the as-crystallised films results in an order of magnitude increase in the DC conductivity and a similar increase in photoconductivity. This is consistent with a shift of the Fermi level position 0.06 eV towards the conduction band. Additionally, analysis of the transient photoconductivity infers a reduced density of states. We discuss the implications of our results for polysilicon TFT optimisation.
Phosphorus Glass Doping of Polycrystalline Silicon During Rapid Thermal Annealing
Authors: Hartiti Bouchaib , Slaoui Abdelilah , Stuck Roland , Muller Jean-Claude , Siffert Paul 
Published: March 2011

ABSTRACTWe show that the use of phosphorus doped spin-on glasses as diffusion source is an attractive approach for the formation of shallow junctions in polycrystalline silicon materials. Moreover, this very simple doping process using a glass film can be fruitfully associated to rapid thermal annealing.
Crystallization of A-Si Films on Low-Melting-Point Glass Substrates
Authors: Park W. K. , Chae G. S. , Givargizov E. I. , Limanov A. B. , Kiselev A. N. 
Published: March 2011

ABSTRACTResults of experiments on crystallization of thin (50 to 200 nm) amorphous Si films initially deposited onto glass substrates by different techniques (PECVD, LPCVD) and treated by different lasers (argon, excimer, or Cu-vapor) are given. The films treated are characterized by in-plane and cross-sectional TEM, and by microdiffraction. Some conclusions about mechanisms of the crystallization are made.
GaAs Quantum Dots by MOCVD
Authors: Fukui Takashi , Ando Seigo 
Published: March 2011

ABSTRACTNew GaAs quantum dots called tetrahedral quantum dots (TQDs) were fabricated using selective area metalorganic chemical vapor deposition (MOCVD). GaAs sub-micron crystals were completely buried in AlGaAs with single growth run without any processing damage at heterojunction interface. The substrates were SiO2 masked (111)B GaAs, which are partially etched free of SiO2 over triangular area using electron beam lithograpy and reactive ion etching techniques. First, truncated tetrahedral AlGaAs buffer layers with {110} facet sidewalls were grown in triangular area. Next, GaAs TQDs were sequentially grown on the top of AlGaAs. Finally, AlGaAs layers were overgrown on the resulting tetrahedral structures. The shape of GaAs tetrahedron was measured by an atomic force microscope(AFM). The size of bottom triangle of GaAs TQDs were estimated to be 20 nm. The size fluctuation was about 2%, which means that uniformity of selective area growth is excellent. Photoluminescence of GaAs TQDs buried in AlGaAs was measured at 8.5K. A clear emission peak from GaAs TQDs was observed at 810 nm. The energy shift from the GaAs emission peak is 19meV, which agrees well with the calculation. The results suggest that the selective area MOCVD method is very promising to fabricate GaAs quantum dots.
Two-Dimensional Damage Distributions Induced by Localized Ion Implantations
Authors: Faye M. M. , Laanab L. , Beauvillain J. , Claverie A. , Vieu C. , Benassayag G. 
Published: March 2011

ABSTRACTA general method is presented for calculating the spatial distribution of damage generated by localized implantation in semiconductors. Implantation through masks and focused ion beam implantation in GaAs are simulated and compared to cross-sectional transmission electron microscopy observations. An excellent agreement is obtained when a depth-dependent lateral straggle is considered. Arbitrarily shaped mask edges and different compositions for the mask and the substrate are included in the calculations as well as realistic current profiles of the ion spot in the case of focused ion beam implantations. Simulations and experiments clearly demonstrate the potential application of localized implantations to fabricate lateral quantum nanostructures.
A Scanning Tunneling Microscopy Study of Mbe-Grown GAAS(001)-Faceted Surfaces
Authors: Maboudian R. , Bressler-Hill V. , Wang X.-S. , Pond K. , Petroff P. M. , Weinberg W. H. 
Published: March 2011

ABSTRACTScanning tunneling microscopy (STM) and reflection high-energy diffraction (RHEED) have been employed to investigate the morphology of faceted GaAs(001) surfaces grown by molecular beam epitaxy (MBE). The RHEED pattern monitored during the growth indicates that the faceting corresponds to (711)A planes. The STM images obtained on these surfaces reveal predominantly a (2×4) local ordering, although unusual (2×3) and (2×6) structures have also been observed. The atom-resolved imaging of the (2×4) structure indicates that the unit cell consists of two As dimers and two missing dimers, identical to the structure obtained on the flat As-rich GaAs(001)-(2×4) surface. Furthermore, islands on the surface are found to be anisotropie, with a shape anisotropy of about 4:1 for step A to step B. The anisotropy is explained in terms of the difference in step edge reactivity.
Luminescence Study of Wet Chemically Etched InP/InGaAs-Submicron-Structures
Authors: Jacobs B. , Zull H. , Forchel A. , Gyuro I. , Speier P. , Zielinski E. 
Published: March 2011

ABSTRACTWe have investigated the optical properties of wet chemically etched InP/InGaAs-wires and dots with widths between 100 nm and 10 μm for different excitation densities. We observe that the non radiative recombination centers at the etched sidewalls can be saturated already at moderate excitation densities about 100 W/cm2. Avoiding saturation effects we obtain a surprisingly large sidewall recombination velocity of 107 cm/sec at 77 K. The comparison of wire and box structures shows that there is no significant difference in the quantum efficiency of both types of structures down to a geometrical size of 160 nm.
Preparation and Chemical Investigation of Porous Silicon
Authors: Poulin S. , Diawara Y. , Currie J. F. , Yelon A. , Gujrathi S. C. , Petrova-Koch V. 
Published: March 2011

ABSTRACTWe have begun a systematic study of the chemistry of light emitting porous Si (LEPOS) using X-ray photoemission spectroscopy and time-of-flight elastic recoil nuclear scattering. The relation of chemical composition to preparation parameters and its evolution with rapid thermal annealing in N2:H2 and in vacuum were studied. The relation between chemical and photoluminescence properties and stability was investigated. The composition of LEPOS is extremely sensitive to preparation conditions and to subsequent treatment. The concentration of C and F in addition to Si, H and O vary with thermal treatment conditions and with time after preparation. However, preparation under the cleanest possible conditions increase both reproducibility and stability.
Magnetopolarons in Quantum-Well Wires
Authors: Wendler L. , Haupt R. , Chaplik A. , Hipólito O. , Osório F. 
Published: March 2011

ABSTRACTThe interaction of quasi-one-dimensional electrons and longitudinal-optical (LO) phonons, placed in a perpendicular magnetic field is calculated. Results are presented for the polaron correction to the Landau levels and the polaron cyclotron mass.
Solution Precipitation of CdSe Quantum Dots
Authors: Kagan Cherie R. , Cima Michael J. 
Published: March 2011

ABSTRACTSynthesis of CdSe quantum dots with a high degree of monodispersity is achieved by nucleation from a supersaturated solution followed by growth to the desired particle size. The effects of temperature on the kinetic mechanisms of nucleation and growth were observed. A reaction vessel equipped with a low thermal mass internal heating element enabled controlled ramping of the solution temperature during the reaction. Nanocrystallite diameter is determined by the reaction time and the solution temperature during particle growth.A method was developed to fabricate ∼1μm thick glass films containing ∼3 vol% CdSe quantum dots. A sol was prepared by mixing a silica organosol with a nanocrystallite dispersion of CdSe and was applied to amorphous quartz substrates by spin-coating. The sols were dried at elevated temperatures in a nitrogen atmosphere. Optical absorbance and fluorescence measurements of the glass film were used to characterize the optical properties of the embedded nanocrystallites. Comparison of the excitonic absorbance of the quantum dot dispersion and the doped glass film shows that particle monodispersity is maintained upon incorporation into the dielectric matrix. Stokes shifts in the band-to-band fluorescence relative to the film absorbance were measured. Shifts in the wavelength of the excitonic absorbance and fluorescence were observed upon incorporation of the quantum dots into the glass film and upon heat treating the glass film to elevated temperatures.
Photoluminescence Excitation Spectroscopy of Cd SxSe(1-x) Nanoparticles
Authors: Stokes Edward B. , Persans Peter D. 
Published: March 2011

ABSTRACTWe present photoluminescence excitation spectra for glasses doped with CdSxSe(1-x). The peak of the emission spectrum is blue shifted toward the bandgap as excitation energy flux is increased. Total photoluminescence emission intensity is observed to be significantly enhanced and blue shifted by exciting with photon energies greater than ∼4 eV. A simple model of the nanoparticle band structure is presented to account for the observed spectra.
Nonlinear Optical Properties of Au Colloid-Doped Glasses
Authors: Kadono Kohei , Sakaguchi Toru , Wakabayashi Hajimu , Fukumi Toshio , Yamanaka Hiroshi , Miya Masaru , Tanaka Hiroshi 
Published: March 2011

ABSTRACTDegenerate four-wave mixing experiments have been performed for Au colloid-doped glasses prepared by melting and sputtering methods. The nonlinear optical properties of the glasses are discussed from viewpoint of the concentration of the Au colloid particles and the thickness of the glasses. We also discuss the dependence of the nonlinear properties on the pulse duration of laser for the measurements, and a very slow relaxation.
Characterisation of Polycrystalline thin Films of Tellurium
Authors: Ray A K , Hogarth C A , Swan R 
Published: March 2011

ABSTRACTStructural, electrical and optical characterisations were performed on tellurium film deposited under high vacuum conditions on ultrasonically cleaned Corning glass 7059 substrates. SEM and TEM studies reveal the polycrystalline nature of deposited tellurium films. At steady state high field conditions, space charge limited conduction is believed to have occurred due to the existence of a fast decaying density of trapping states in the energy gap. The DC conductivity is believed to exhibit a T-1/ law dependence below room temperature, giving a value of 2×10-l6eV/m3 for conduction states close to the Fermi level. From the power law dependence on frequency of AC conductivity, the barrier for bipolaron hopping is estimated to 0.33eV.Optical absorption in 9nm thick tellurium samples is due to direct transitions both allowed and forbidden producing two edges, the first one at 4eV and the other at about 0.5eV, respectively.
Deposition of Fluorine Doped Tungsten Oxide Thin Films by Atmospheric Pressure Chemical Vapor Deposition
Authors: Proscia James W. , Winter Charles H. , Reck Gene P. , Wen Gang Gang 
Published: March 2011

ABSTRACTPolycrystalline fluorine doped tungsten oxide thin films were deposited onto glass substrates by reacting tungsten hexafluoride, difluoroethane, and isopropanol. The reaction was performed in an atmospheric pressure chemical vapor deposition reactor at a temperature of approximately 400 °C. The electrical conductivity and spectral properties were suggestive of n-type substitutional doping in which oxygen is partially replaced by fluorine. Temperature dependent resistivity measurements were consistent with the presence of polarons. The films were blue in color with enhanced reflectance and absorbance in the IR. These optical characteristics are potentially useful in improving the solar control properties of glass. Scanning electron microscopy revealed a faceted surface morphology. The fluorine atom concentration decreased when the films were annealed in air.
Quantum Size Effect in Metal Coated Nanoparticles
Authors: Zhou H. S. , Honma I. , Komiyama H. , Haus J. W. 
Published: March 2011

ABSTRACTIn this paper we report the synthesis of Au2S nanoparticles with a gold coating on the surface; the particles are characterized by transmission electron microscopy (TEM), electron diffraction and absorption data. The absorption spectrum is recorded during the gold coating growth process; this data demonstrates a large resonance shift during the growth process. The results are consistent with the growth of a metal shell around the particles; the theoretical model includes electron quantum confinement in the metal shell. The size dependence of the frequency shift, as well as the width of the resonance are consistent with the model.
Paramagnetic Nitrogen Defects in Silicon Nitride
Authors: Warren W. L. , Kanicki J. , Robertson J. , Poindexte E. H. 
Published: March 2011

ABSTRACTThe photocreation mechanisms and properties of nitrogen dangling bonds in amorphous hydrogenated silicon nitride (a-SiNx:H) thin films are investigated. We find that the creation kinetics are strongly dependent on the post-deposition anneal; this thermal process can be described by a simple exponential function which yields an activation energy of 0.8 eV. The compositional dependence of the nitrogen dangling bond center suggests that its energy level lies close to the valence band edge, in agreement with theoretical calculations. This energy level position can explain why a-SiNx:H films often become conducting following a high post-deposition anneal.
Thermal Stability of a-SiNx:H Films
Authors: Kudoyargva V.Kh. , Aivazov A. A. , Budaguan B. G. , Filatova I. V. 
Published: March 2011

ABSTRACTThe investigations of thermal stability of a-SiNx:H films (x≤0.4) have xbeen performed bv both IR spectroscopy and DTA techniques. The properties of samples with x≤0.06 were attentively considered because in this case the nitrogen may be treated as an impurity in a-Si:H. It has been shown that controlled nitrogen doping (up to 0.5 Pa NH3) can be used as an effective technique for thermostabilization of a-Si:H properties.
Prolonged Storage of Electrons in Monos-Structures
Authors: Maslovsky Vladimir M. , Simanovich Ellen V. 
Published: March 2011

ABSTRACTThe transient process of the accumulation of charge in the Silicon Nitride by applying a positive voltage pulse to MONOS structure is investigated with the help of the experimental and theoretical methods (monopolar injection of electrons). The mathematical model of charge carriers transport in an amorphous nitride thin films in MONOS structures at the high electric fields has been developed. The essential peculiarity of this modelis that the injected carriers from the contact are captured by a quasi - continuous spectrum of states that there are traps, having an exponential distribution of densityin the nitride band gap and by the monoenergetic positively charged deep centers. The positive traps are made by the negative correlation energy defects. These defects are formed by the weak quasi- hydrogenous bonds Si-H-Si the changes of ones in consequences of a migration of hydrogen stipulate for the degradation processes in the nitride. It is established that the quasi - distributed traps are answered for the prolonged relaxation of current in the external circuit when t≫Tg in which the exponent α of function J∼t-α is determined by the parameter of the energy distribution of traps and by the applied voltage on the structure that is in agreement with experimental results and corresponds to the dispersive transport of carriers.
The Effects of Silicon Source Gas on PECVD SiO2 Properties
Authors: Burns James A. , Gleason Edward F. 
Published: March 2011

ABSTRACTSilicon dioxide was plasma-deposited at 300C using either the reaction of silane and nitrous oxide or the reaction of tetraethylorthosilicate with oxygen. The structural and electronic properties of films produced by both reactions were studied as functions of post-deposition heat treatments. The former reaction produced films which were more dense and less conductive than the latter. A model was developed to determine the amount and location of charge in the deposited films. The charge was found to be dependent on the reaction and the post-deposition anneal.
Hydrogen in RF Reactive Magnetron Sputtered Silicon Nitride Films
Authors: Lin Chi-Hsien , Wachtman J. B. , Sigel G. H. , Pfeffer R. L. , Monahan T. P. , Lareau R. T. 
Published: March 2011

ABSTRACTABSTRACT: Silicon nitride films (a-SixN1−x:H) have been prepared by rf reactive magnetron sputtering from a silicon target in a mixture gas of Ar, N2, and H2. The effects of the presence of hydrogen gas have been related to the refractive index, deposition rate, etch rate, and the Si-H and N-H bonding in the films. Hydrogen contents were measured by a quadrupole secondary ion mass spectrometer (SIMS) using deuterium implanted samples as reference standards. The deuterium implanted samples were annealed at 900°C for various periods of time to study the diffusion behavior of deuterium and hydrogen in a Si-rich and a nearly stoichiometric silicon nitride film.
Study of SiF4-N2-H2 Plasmas for the Deposition of Fluorinated Silicon Nitride Films
Authors: Cicala G. , Bruno G. , Capezzuto P. , Losurdo M. 
Published: March 2011

ABSTRACTRadiofrequency glow discharges, operating under various conditions, have been used to deposit hydrogenated and fluorinated silicon nitride (a-Si,N:H,F) from SiF4-N2-H2 gas mixtures. The effect of the feeding mixture composition has been investigated in order to establish the optimum deposition conditions for stable silicon nitride. High H2-dilution of the feeding mixture has been found to produce transparent (Eg>5.6eV) and stoichiometric (N/Si=1.3) films.
Interaction of Atonic Hydrogen with Ion Bombardment Induced Defects at Si/SiO2 Interfaces
Authors: Kar S. , Ashok S. 
Published: March 2011

ABSTRACTElectrically active traps were induced in the Si-SiO2 interfacial region by silicon ion bombardment. A Kaufman source was used to introduce 400 eV hydrogen ions into the oxide and the interface. The interaction of the hydrogen species with the traps was monitored by a comprehensive set of electrical measurements of the metal-oxide-silicon [MOS] structures.