bluuebunny/crossref_metadata_2025_split huggingface dataset:
Foreign Gas Effect upon Excimer Laser Ablation of Polymer
Authors: Shimo N. , Uchida T. , Masuhara H. 
Published: March 2011

ABSTRACTWe have examined effect of foreign gas and its pressure upon etch rate, surface morphology, and surface chemical composition. Etch rate is suppressed by adding inert gases such as argon and helium. On the contrary, oxygen enhances the rate by increasing its pressure, indicating that oxygen molecules react with ablated polymer surface. From the results of XPS analyses, active surface of ablated polymer reacts also with ammonia and hexamethyldisilane. It is considered that laser ablation has a high potentiality of simultaneous microfabrication and photochemical surface modification of polymer.
Pulsed Laser Deposition of Magneto-Optic Material
Authors: Erington K. B. , Mcgahan W. , Ianno N. J. , Woollam J. A. 
Published: March 2011

ABSTRACTA wide range of materials can be deposited by Pulsed Laser Deposition. We will discuss the deposition of materials that can be employed in magneto-optic systems. These materials include dysprosium, cobalt, and aluminum nitride. We will present the results of our work involving the fabrication of multilayer structures of the previously mentioned material. These structures and materials have been characterized by a scanning electron microscope (SEM) and X-ray diffractometry
Effects of Interfaces on the a-Si:H Schottky Barrier Characteristics
Authors: Li Y. M. , Malone C. , Kumar S. , Wronski C. R. , Nguyen H. V. , Collins R. W. 
Published: March 2011

ABSTRACTA detailed study of hydrogenated amorphous silicon (a-Si:H) surfaces during etching and subsequent low temperature (T≤200°C) oxidation was carried out using in-situ and spectroscopic ellipsometry (SE). The microstructural information from SE is correlated with the properties of the corresponding evaporated Pd Schottky barrier structures. Oxide layers thinner than ∼ 10 Å have little effect on the diode characteristics and electron surface recombination velocities. This is consistent with a porous structure for these oxides. Evidence is found from growth kinetics that higher density, compact oxide growth occurs for greater thicknesses. These oxides have a large effect on electron transport and surface recombination velocities consistent with the formation of metal-insulator-semiconductor structures.
Optical Characterization of Interface, Surface and Bulk Defects in A-Si:H
Authors: Persans P. D. , Arnzen D. , Possin G. E 
Published: March 2011

ABSTRACTWe present a new analysis approach which combines photoconductivity and photother-mal deflection spectroscopies in a-Si:H thin films of various thicknesses to profile electronic defects.
High Quality Interfaces in a-Si:H/a-Sic:H Superlattices
Authors: Bernhard N. , Kirsch M. , Eigenschenk R. , Bollu M. , Wetzel C. , Müller F. , Schwarz R. 
Published: March 2011

ABSTRACTAmorphous multilayers with low interface defect density were deposited in an ultrahigh-vacuum RF-glow discharge reactor by computer-controlled fast gas switching. An extensive film characterization was done including determination of carbon content by PES (proton enhanced scattering), grazing-incidence X-ray diffraction, measurement of ambipolar diffusion length, FTIR spectroscopy and hydrogen effusion. From PDS (photothermal deflection spectroscopy) a defect density of below 1011 cm−2 per interface is found.
Study of Band Tails in a-SiGe:H Alloys from Time of Flight and Thermally Stimulated Current Experiments
Authors: Longeaud C. , Kleider J. P. , Mencaraglia D. , Mohammed-Brahim T. , Rahal A. 
Published: March 2011

ABSTRACTThermally stimulated current (TSC) and Time of flight (TOF) experiments have been performed on the same set of Pt/a-SiGe:H Schottky diodes in order to compare the band tail characteristics obtained from the two methods. For the silicon rich alloys, good agreement is found in the values of the band tail width. However, the values of the attempt-to-escape frequencies obtained from TSC are typically orders of magnitude smaller than those obtained from TOF. To analyse the origin of this discrepancy we propose another kind of TSC experiment denoted Pulsed TSC: short voltage pulses are applied to the sample while it is heated and the resulting current is monitored. Preliminary results are presented and discussed .
Studies on Carrier Transport Through a-Si:H/a-Si1−xCxH Quantum Well Structures Imbedded in the i Layer of a p-i-n Structure
Authors: Jiang Y. L. , Hwang H. L. , Feng M. S. 
Published: March 2011

ABSTRACTa-Si:H/a-Si1−XCX:H single and double barrier structures imbedded at different locations of the i layer of a p-i-n structure were used to study the carrier transport properties of amorphous QW. The shapes of the observed I-V curves of both structures are similar. The bound states of the well layer of double barrier structures do not play a role in the carrier tunneling process. The resonant tunneling time is larger than the inelastic scattering time by 5 to 12 orders of magnitude. When the tunneling process of amorphous QW is in the completely incoherent tunneling regime, the peak-to-valley ratio of NDR and the density of states in the well go to zero. From the analysis of I-V characteristics of both structures under different monochromatic light illumination, the observed current dips are due to the collection of photogenerated carriers in two regions of the i layer separated by the imbedded barrier structure.
Photoinduced Noise in Amorphous Semiconductor Films
Authors: Demichelis F. , Pirri C.F. , Tagliaferro A. 
Published: March 2011

ABSTRACTElectrical noise measurements have been performed on amorphous semiconductor films under irradiation with monochromatic light at different wavelengths. The Power Spectrum Densities (PSDs) of highly photoconductive undoped a-Si:H and a-SiC:H (deposited by glow discharge) in the frequency range .1 – 20 kHz are obtained at room temperature. The analysis is performed upon metal/semiconductor/ITO Schottky barriers. The PSDs vs frequency follow l/fn law and show a change of magnitude when the wavelength of the incident light is varied around the value corresponding to the energy gap.
Proximity Recovery Layers to Speed up the Recovery of Stressed Amorphous Silicon Thin-Film Transistors
Authors: Hack M. , Jackson W. B. , Lujan R. 
Published: March 2011

ABSTRACTWe have developed a means to speed up the recovery of both the threshold voltage shift of hydrogenated amorphous silicon (a-Si:H) transistors and the Vx shift of high voltage a-Si devices. This is accomplished by placing a lightly doped compensated layer adjacent to the active layer in these transistors. This proximity recovery layer does not alter the initial characteristics of a-Si:H transistors and is completely process compatible with standard fabrication procedures.
Thermal-CVD Produced Amorphous-Silicon Thin-Film Transistors-Ambipolar Characteristics
Authors: Kanoh Hiroshi , Sugiura Osamu , Breddels Paul A. , Matsumura Masakiyo 
Published: March 2011

ABSTRACTAmorphous-silicon thin-film transistors (a-Si TFTs) have been fabricated by using an a-Si layer deposited by low-temperature thermal-CVD method using higher silanes. The TFT with thermally grown SiO2 gate was operated in both the n-channel mode and the p-channel mode. The maximum field-effect mobility and typical on/off current ratio were 1.5 cm2/Vs and 107 for the n-channel operation, and 0.2 cm2/Vs and 106 for the p-channel operation, respectively. Free electron mobility in the conduction band and free hole mobility in the valence band have been estimated, using the temperature dependence of the field-effect mobilities. It was found that the hole mobility is as high as the electron mobility.
Threshold Voltage Shifts in Amorphous Silicon Thin Film Transistors under Bias Stress
Authors: Ogawa Tetsu , Hotta Sadayoshi , Takezawa Horoyoshi 
Published: March 2011

ABSTRACTThrough the time and temperature dependence measurements on threshold voltage shifts (Δ VT) in amorphous silicon thin film transistors, it has been found that two separate instability mechanisms exist; within short stress time ranges Δ Vτ increases as log t and this behavior corresponds to charge trapping in SiN. On the other hand, in long stress time ranges Δ VT increases as t t/4 and can be explained by time-dependent creation of trap in a-Si.
Measurements of 1/f Noise in A-Si:H Pin Diodes and Thin-Film-Transistors
Authors: Cho Gyuseong , Drewery J. S. , Fujieda I. , Jing T. , Kaplan S. N. , Perez-Mendez V. , Qureshi S. , Wildermuth D. , Street R. A. 
Published: March 2011

ABSTRACTWe measured the equivalent noise charge of a-Si:H pin diodes (5 ∼ 45 μm i-layer) with a pulse shaping time of 2.5 μ.sec under reverse biases up to 30 V/μm and analyzed it as a four component noise source. The frequency spectra of 1/f noise in the soft-breakdown region and of the Nyquist noise from contact resistance of diodes were measured. Using the conversion equations for a CR-RC shaper, we identified the contact resistance noise and the 1/f noise as the main noise sources in the low bias and high bias regions respectively. The 1/f noise of a-Si:H TFTs with channel length of 15 μm was measured to be the dominant component up to ∼100kHz for both saturation and linear regions.
Amorphous Silicon Sensor Arrays for Radiation Imaging
Authors: Street R. A. , Nelson S. , Antonuk L. , Perez Mendez V. 
Published: March 2011

ABSTRACTLarge two-dimensional a-Si:H imaging arrays have applications in imaging of X-ray, gamma-ray and charged particle fluxes. Radiation imaging using a-Si:H p i n sensors together with a phosphor to transform the radiation into visible light is described, and some examples of images are shown. These arrays are very efficient in imaging large area diffuse sources, and the a-Si:H sensors have little radiation damage. The main limitation to the sensitivity of the array is the leakage current of the sensors, which is a source of noise and limits the integration time of the arrays. The contributions to the leakage current from bulk thermal generation and contact injection are discussed
Tunneling Assisted Photocurrent Multiplication in a-Si Based p-i/Sinx/i-n Structure Junction
Authors: Yoshimi M. , Hattori K. , Okamoto H. , Hamakawa Y. 
Published: March 2011

ABSTRACTPhotocurrent multiplication has been observed in a-Si based p−i/SiNx/i−n junction cells under reverse biased high electric field. An apparent external quantum efficiency exceeds 20. A systematic investigation on electric and optoelectronic properties has been made to clarify the mechanism of photocarrier multiplication. The results indicate the possibility of inter-band tunneling via localized states in the a-SiN layer, which is induced by field-redistribution due to the built-up of trapped charges at the a-SiN/a-Si interface.
Nmr and Esr Studies of the Structural Defects of Amorphous and Microcrystalline Sic Prepared by the Polymer Route
Authors: Ting S.-J. , Chu C.-J. , Mackenzie J.D 
Published: March 2011

ABSTRACTAmorphous SiC was prepared by firing the polycarbosilane to various temperatures ranging from 500°C to 1200°C. However the l3c CPMAS NMR and ESR studies show that the carbon rich SiC has two major structural defects, C=C bonds and C-dangling bonds. Both defects concentrations vary with different sample firing conditions. Hydrogen has dramatic effect on decreasing the defect concentrations when used in the sample firing.
Direct a-Si:H Photo-CVD Deposition with the Excimer Spectra of a Dielectric-Barrier Discharge Lamp
Authors: Kessler F. , Mohring H.-D. , Bauer G.H. 
Published: March 2011

ABSTRACTA vacuum UV-photo-CVD reactor for direct decomposition of Si2H6, SiH4, GeH4, and B2H6 for a-Si:H, a-Ge:H, and a-SiGe:H deposition has been operated with a large area dielectric-barrier discharge lamp emitting excimer radiation of Xe (7.3eV), Kr (8.6eV), or Ar (9.8eV).It is shown that the deposition process (Si2H6 or GeH4 at 0.5 mbar) is governed by the diffusion of long-lifetime radicals.High quality undoped and p-type doped a-Si:H has been deposited from Si2H6 and B2H6 with the Xe lamp spectrum (σph/σ≈106 at Eg=1.9eV) and film growth rates of up to 5 nm/min have been achieved.
Deposition of a-Ge:H in a Remote Plasma System
Authors: Heintze M. , Nebel C. E. , Bauer G. H. 
Published: March 2011

ABSTRACTThe remote plasma deposition process was studied by optical emission spectroscopy using Ne and N2 to detect He-metastables. a- Ge:H was prepared and its optoelectronic and structural properties were characterized. AM 1.5 photoconductivities around 10−6(Ωcm)−1 were obtained in intrinsic material with the Fermi level position lying near midgap. However, even in the best film the defect density is higher than 1017cm−3.
Hydrogen Incorporation in Amorphous Silicon Prepared at High Deposition Rates by the VHF-GD Technique
Authors: Finger F. , Viret V. , Shah A. , Tang X.-M. , Weber J. , Beyer W. 
Published: March 2011

ABSTRACTThe influence of deposition temperature on hydrogen incorporation in a-Si:H prepared by VHF glow discharge at 70 MHz is investigated using hydrogen evolution, elastic recoil detection analysis and infrared spectroscopy.The films were further characterized by dark- and photoconductivity and by photothermal deflection spectroscopy. While the electronic film properties deteriorate in the usual manner with decreasing substrate temperature it is found that the total hydrogen content CH and the degree of microstructure that can be directly correlated to CH increase only moderately. It is concluded that a higher flux of low energy ions in the VHF plasma plays a key role in this context, possibly by increasing the surface mobility of the H atoms and thereby preventing the build-in of a large amount of hydrogen at low substrate temperatures.
Energy Resolved Mass Spectrometry of the a-Si:D Film Growth Species During DC Magnetron Sputtering
Authors: Myers A. M. , Ruzic D. N. , Maley N. , Doyle J. R. , Abelson J. R. 
Published: March 2011

ABSTRACTDouble modulated beam mass spectrometry was used to obtain the first measurements of the identity, relative flux, and energy of film precursors in reactive dc magnetron sputtering. In these experiments, a 2″ diameter silicon target was sputtered in an argon plus deuterium plasma at an argon pressure of 1.5 mTorr. This system produces high quality a-Si:D. Energetic neutral Si and SiD were observed, while energetic neutral SiD2 and SiD3 were absent. The arrival rate of D in the form of SiD increased and then saturated at 19 percent of the total flux as the deuterium pressure was varied from 0 to 5 mTorr. The sputtered Si energy agreed qualitatively with the standard Thompson theory. Energetic ions located at mass 2 and 4 were measured with energies much greater than the sputtered Si. Thermal silane was also detected, raising the possibility that thermal silane radicals in addition to energetic Si and SiD contribute to film growth.
Annealing of Defects During the Deposition of Amorphous Silicon
Authors: Hata N. , i Cabarrocas P. Roca , Wyrsch N. , Wagner S. , Favre M. 
Published: March 2011

ABSTRACTThe thickness dependence of the sub-gap optical absorption in plasma-deposited hydrogenated amorphous silicon is carefully studied by photo-thermal deflection spectroscopy. The deep-level defect concentration decays from the top surface into the bulk where it approaches the thermal equilibrium defect density. This defect profile is interpreted in terms of the annealing, during growth, of growth-induced surface defects. It is also shown that the defect profile is compatible with the known growth-temperature dependence of the average defect density in amorphous silicon.
Characterization of a-Si:H,Cl and a-Sic:H Films Prepared by Electron Cyclotron Resonance Plasma
Authors: Gangopadhyay S. , Trost T. , Kristiansen M. , Young C. , Zheng P. , Palsule C. , Pleil M. 
Published: March 2011

ABSTRACTMicrowave excited electron cyclotron resonance (ECR) plasmas have been used to fabricate a-Si:H,Cl and a-SiC:H films. By varying the absorbed microwave power, highly photoconductive a-Si:H,Cl films were obtained. The a-SiC:H films do not have appreciable photoconductivity, but they show a bright, broad continuous wave (cw) photoluminescence (PL) in the visible region under near-uv excitation. We have measured the photoluminescence decay in the picosecond range and have resolved the spectra into four distinct components. The four luminescence components may correspond to various recombination mechanisms of photogenerated electron-hole pairs.
A New General Method for the Determination of Optical Properties of Amorphous Silicon Films
Authors: Amato G. , Boarino L. , Fizzotti F. , Manfredotti C. 
Published: March 2011

ABSTRACTWe propose to apply a new method to model the optical response of amorphous silicon thin films. This method presents the advantage of having a good physical insight. On the other hand, although the model has been originally tested on different materials like a-Si, a-Ge and a-GaAs, we show that it is also sensitive to small differences like those that can exist between intrinsic and doped a-Si:H.
Optimization of Textured Tco Substrates for a-Si Solar Cells
Authors: Komakine Mitsuhiko , Nishimura Hiromichi , Gotoh Yoshio , Sato Kazuo , Kondo Kei 
Published: March 2011

ABSTRACTTextured TCO (Sn02:F) substrates were fabricated using atmospheric pressure CVD (APCVD). Various kinds of TCO developed were classified into three types (A, B, C) in terms of shape of texture, electrical and optical properties. TCO substrates of type A with low carrier concentration and pyramidal texture fulfill the conflicting properties of low absorption and low resistivity after hydrogen plasma treatment. By using type A TCO substrates, the highest conversion efficiencies of 12 % for a small area of 1cm×1cm as a-Si single junction solar cell were certified by several related NEDO research organizations.
Light-Induced Electron Spin Resonance in Gate-Quality Nitrogen-Rich Amorphous Silicon Nitride: Photo-Production and Photo-Bleaching
Authors: Tober E. D. , Crowder M. S. , Janicki J. 
Published: March 2011

ABSTRACTElectron spin resonance spectroscopy is used to monitor the light-induced, paramagnetic (neutral) defect density in gate-quality nitrogen-rich hydrogenated amorphous silicon nitride (a-SiN1.6:H) thin films. A new phenomenon has been observed in which the light-induced electron spin resonance (LESR) signal can be reduced (photo-bleached) by re-illuminating with monochromatic light. The extent to which the LESR signal is bleached depends strongly upon the incident photon energy used for re-illumination. Photo-bleaching as well as the photo-production of the LESR signal follow a stretched exponential dependence upon illumination time.
Annealing of Irreversible Defects in Hydrogenated and Unhydrogenated Amorphous Silicon Thin Films
Authors: Parsons G. N. , Wang C. , Lucovsky G. 
Published: March 2011

ABSTRACTWe have prepared unhydrogenated and hydrogenated ([H] = 14 at.%) amorphous silicon thin films using magnetron sputtering with substrate temperature, TS = 40°C. After deposition, the films were annealed at temperatures between 150 and 200°C and conductivity was measured as a function of anneal time. We find that for that for both materials, the conductivity changes non-exponentially with annealing time. The characteristic time constant for annealing at 175°C is approximately the same in unhydrogenated films (τ≈100min) as found in films containing 14 atomic % hydrogen (τ≈200min).
Defect Density in Doped a-Si:H Films
Authors: Pierz K. , Mell H. , Fuhs W. 
Published: March 2011

ABSTRACTWe compare the experimentally observed correlation between the density of charged dangling–bond defects and the Fermi–level position in n– and p–type a–Si:H films with the predictions of two hydrogen–related models for the thermal equilibrium state at the glass–transition temperature of the hydrogen glass in a–Si:H. Reasonable agreement is obtained with a defect reaction in which the transfer of hydrogen from Si–H bonds to weak bonds is limited to distances comparable to one atomic spacing. The results for p–type (boron–doped) films suggest that the formation of positively charged dangling–bond defects is not only determined by electronic energy differences but also by a relaxational energy gain of approximately 0.2eV.
Forces and Geometry Optimization in First-Principles Atomic Cluster Calculations
Authors: Jackson Koblar , Pederson Mark R. , Erwin Steven C. 
Published: March 2011

ABSTRACTWe make use of the existing formalism for calculating atomic forces within the local density approximation (LDA) to determine forces in all-electron, local orbital electronic structure calculations. The forces are calculated as the proper total energy derivatives, including the necessary basis-set corrections. Our technique evaluates the LDA potential exactly on a variationally determined integration mesh which allows all integrals relevant to the electronic structure problem to be computed to any desired accuracy. We demonstrate the high accuracy of forces calculated using our method with an application to the molybdenum dimer. Several issues concerning the accuracy of the forces are discussed, including self-consistency effects, and the effects of integration error. We discuss the use of the forces in dynamical routines for geometry optimizations.
Theory of the Quasiparticle Effective Masses in Semiconductors based on an Electron Self Energy Approach
Authors: Zhu Xuejun , Hybertsen Mark S. , Louie Steven G. 
Published: March 2011

ABSTRACTA conceptually complete formalism for the quasiparticle effective masses in semiconductors is proposed. Our approach is based. on a generalized form of the theory, including the effects of the nonlocal, energy dependent electron self: energy operator Σ, which accounts for the electron-electron interaction. This introduces two -important effects on the expression of the effective mass: an explicit energy renormalization and an extra contribution to the matrix element that enters the usual . Our preliminary numerical results for prototypical GaAs show promising improvements over the results from the local density approximation for the calculated electron effective mass compared to experimental data.
On the Possibility of Passivation of Si(100) by Adsorption of Group-VI Atoms
Authors: Kaxiras Efthimios 
Published: March 2011

ABSTRACTThe possibility of passivating the Si(100) surface by adsorption of Group-VI atoms (S and Se) is investigated through first-principles calculations. The structure of the ideal (1×1) configuration with the Si surface dangling bonds saturated by full monolayer coverage is examined in detail. The Group-VI adsorbates form covalent bonds to the substrate with bond-lengths very close to the sums of the covalent radii. The bond-angles are larger than in bulk configurations of the Group-VI elements. The ideal (1×1) configuration gives rise to a surface electronic state with large dispersion spanning the entire band-gap of Si. Deviations from this configuration by in-phase or out-of-phase tilting of the adsorbate atoms result in energy costs which can give qualitative information on the relative strength of adsorbate-adsorbate and adsorbate-substrate interactions.