bluuebunny/crossref_metadata_2025_split huggingface dataset:
Novel Application of Amorphous Silicon in Electrostatic Loudspeakers
Authors: Schropp R. E. I. , Smits M. , Meiling H. , van Sark W.G.J.H.M. , Boone M. M. , Bezemer J. , van der Weg W. F. 
Published: March 2011

ABSTRACTA thin film of amorphous silicon (a-Si:H) has been developed for application as the charge retention layer in electrostatic loudspeakers. The vibrating diaphragm in this type of loudspeakers is usually coated with a thin film in order to assure homogeneous charge distribution across the surface. This thin film should be capable of maintaining a high surface charge density and possess a high lateral resistivity to prevent charge displacement. Furthermore, it should be mechanically stable, capable of accomodating mechanical deformation, and resistant against humidity. Conventionally, a graphite layer is used in these applications. However, the conventional layers are frequently unstable and suffer from charge displacement effects eventually leading to electric breakdown. Further requirements are that the film can be deposited continuously and homogeneously over large areas in excess of 1 m2 and that the deposition technique is compatible with the properties of the thin membrane. We investigated small-area prototypes of electrostatic loudspeakers with a-Si:H thin films deposited on polyimide substrates in the Utrecht deposition system, ASTER. Plasma-deposited amorphous silicon films fabricated under certain conditions are shown to meet all of the above requirements.
Light-Response Characteristics of Amorphous Silicon Arrays for Megavoltage and Diagnostic Imaging
Authors: Antonuk L. E. , Yorkston J. , Kim C. W. , Huang W. , Morton E. J. , Longo M. J. , Street R. A. 
Published: March 2011

ABSTRACTLight-sensitive hydrogenated amorphous silicon pixel arrays are now under development for real-time megavoltage and diagnostic fluoroscopic imaging. Such applications place stringent demands upon a variety of array properties including the uniformity of the light-response function of the pixels. It is desirable that the design and fabrication of these imaging arrays maximize such uniformity. The implications of uniformity for imaging are reviewed, and data obtained from small arrays are presented and discussed.
Defect Structure and Network Disorder in Boron Doped Amorphous Silicon
Authors: Schubert M. B. , Schumm G. , Lotter E. , Eberhardt K. , Bauer G. H. 
Published: March 2011

ABSTRACTA series of boron doped a-Si:H films have been characterized by PDS, FTIR, Raman, and SIMS in order to evaluate the effects of boron incorporation on structural properties and hydrogen bonding. Doping by B2H6 or B(CH3)3 does not significantly enhance the overall disorder of the silicon network showing up in the TO-like Raman halfwidth whereas remarkable changes in local, defect related structures are evident from PDS. An analysis of the data suggests two bands of defects in the pseudogap at low boron concentration and only one band for higher concentration. To account for Fermi level positions, shifts of the hole transport path well into the valence band tail upon doping must be invoked.
Effect of the Local Disorder in a-Si on the Electronic Density of States at the Band Edges.
Authors: Davidson B. N. , Lucovsky G. , Bernholc J. 
Published: March 2011

ABSTRACTWe have systematically investigated the formation of electronic states in the region of the conduction and valence band edges of a Si as functions of variations in the bond angle distributions. Local Density of States (LDOS) for Si atoms in disordered environments have been calculated using the cluster Bethe lattice method with a tight-binding Hamiltonian containing both first and second nearest neighbor interaction terms. LDOS for atoms with bond angle dis ortions in the nearest neighbor and second neighbor shells are compared and contrasted, both showing an influence on the LDOS near the gap. We also consider the role of the second neighbor term in the Hamiltonian by comparing the DOS for a distoned infinite Bethe lattice using Hamiltonians with and without the second neighbor interactions. It is found that in this case the second neighbor interaction terms cause greater conduction band tailing than using the nearest neighbor interaction terms alone.
The Distribution of Occupied Deep Levels in a-Si:H Determined from CPM Spectra
Authors: Hata Nobuhiro , Wagner Sigurd 
Published: March 2011

ABSTRACTWe report the determination of the distribution of occupied defect states in hydrogenated amorphous silicon from the deconvolution of constant photocurrent measurement (CPM) spectra, and the modelling of the distribution with the defect pool.The CPM spectra were taken on undoped a-Si:H samples either in their as-grown state, in the annealed state, after quenching from high temperature, or after light-soaking. The spectra were deconvoluted to account for transitions from deep levels and from valence band tail states to a conduction band assumed to have a sharp edge. As-grown or annealed-state samples show a peak at 1.0 eV (0.2 eV FWHM) below the conduction band edge. Assuming a mobility gap of 1.9 eV, this peak lies 0.9 eV above the valence band edge. We ascribe this peak to the Do/+ transition. CPM spectra of light-soaked and thermally quenched samples show shifts in the peak position and increases in die peak height in accordance with the defect pool model. The model calculations agree with the CPM results, so that the applicability of CPM spectral analysis to obtaining detailed values of defect pool parameters is demonstrated.
Charge-Defect Equilibrium Description of the Staebler-Wronski Defect Concentration and Formation Energy
Authors: Fortmann C. M. , Dawson R. M. , Wronski C. R. 
Published: March 2011

ABSTRACTAn equilibrium framework for the high temperature behavior of dangling bond defects in amorphous materials is developed. With this framework it is possible to relate the thermal formation of defects directly with those created by high temperature illumination or current injection. It is found that the free energy change associated with dangling bond formation is negative. The negative free energy change means that if one considered only the structural changes, the lowest energy state for the system is with the weak bonds split into neutral and charged dangling bonds!
A Novel Preparation Technique Termed “Chemical Annealing” to make a Rigid and Stable Si-Network
Authors: Shirai Hajime , Hanna Jun-Ichi , Shimizu Isamu 
Published: March 2011

ABSTRACTA novel preparation technique termed “Chemical Annealing (CA)” was developed with aim of making a stable and rigid structure of Si-network. The a-Si:H films were made by the alternate deposition of several tens angstrom thick a-Si:H and the treatment with atomic hydrogen or excited novel gases such as Ar* and He*. Hydrogen contents (CH) and optical gap (Eg) in the film prepared by this tecnique were able to reduced by CH of 1.5at%, and Eg of 1.5eV, respectively at substrate temperature:300C. All of them exhibited high photoconductivities in the level of 10-5 10-4 S/cm under illumination of 100mW/cm2. In the films with CH of 3at% or less, in particular, marked improvement was confirmed in the stability after light soaking. In addition, the time-of-flight measurement revealed a non-dispersive transport and a significant enhancement in the drift mobility of holes up to 0.2cmm2/Vs at room temperature in the film with CH : 5at% and Eg:1.65eV prepared at 300C. Advantages of the CA process are summarized together with the discussion of role of atomic hydrogen, excited novel gases such as Ar* and He* in the growing surface.
Film Deposition Process in Pulse Discharge CVD
Authors: Yoshida T. , Fujisawa H. , Hokaya T. , Ichikawa Y. , Sakai H. 
Published: March 2011

ABSTRACTTo understand the deposition process of pulse discharge (PD) CVD, we studied spatial distribution and decay of plasma parameters and those of SiH LIF signals. In addition, we studied film properties of a-SiC:H and a-SiGe:H deposited by the PD-CVD. It was found that the quality of p-type a-SiC:H films deposited by the PD-CVD from SiH4+CH4+B3 was better than those of conventional p-type a-SiC:H films. The p-type a-SiC:H films were applied to the p-layer of p-i-n a-Si solar cells, and a conversion efficiency of 12. 3% was obtained for a 1cm2.
Deposition of Device Quality, Low H Content a-Si:H by the Hot Wire Technique
Authors: Mahan A. H. , Nelson B. P. , Salamon S. , Crandall R. S. 
Published: March 2011

ABSTRACTWe report measurements of the Urbach edge, optical bandgap, and ambipolar diffusion length on a series of hydrogenated amorphous silicon (a-Si:H) films deposited by hot-wire-assisted chemical vapor deposition (HW). We compare the properties of these films to those of a series of a-Si:H films deposited by the traditional radio frequency (rf) glow discharge (GD) technique, where we varied the substrate temperature to change the bonded H content (CH). We show for the first time that, as CH is decreased below the value traditionally associated with device quality GD a-Si:H (∼10 at.%), the electronic properties of the GD films deteriorate in the traditional manner while those for the HW samples remain device quality. Properties of these low CH HW samples will be presented and compared to those of GD films containing comparable CH. Because several indications exist that the structure of the HW films is different than that of the GD films, Raman and Small Angle X-Ray Scattering (SAXS) measurements are presented to illustrate structural differences.
Correlation Between Freeze-In Temperature of Defect Density and Hydrogen Concentration in a-Si:H
Authors: Xu X. , Isomura M. , Yoon J. H. , Wagner S. , Abelson J. R. 
Published: March 2011

ABSTRACTWe measured the freeze-in temperature of the dangling-bond density in a-Si:H in nine samples with hydrogen concentrations ranging from 7.0 to 31 at.%. The measurements were made by determining the defect density of samples quenched from successively higher temperature. We determined the defect densities with the constant photoconductivity method. The freeze-in temperature is 211±10 °C, and is independent of hydrogen concentration.
Amorphous Silicon Selenium Alloy Film Deposited Under Hydrogen Dilution
Authors: He Muzhi , Lin Guang H. , Bockris J. O'M. 
Published: March 2011

ABSTRACTAmorphous silicon selenium alloy films were prepared by plasma enhanced chemical vapor deposition with hydrogen dilution. The flow rate ratio of hydrogen to silane was about 8:1. Amorphous silicon selenium alloy was found to have an optical bandgap ranging from 1.7 eV to 2.0 eV depending on the selenium concentration in the films. The light to dark conductivity ratios of the alloy films are ∼ 104. The optical and electrical properties, Urbach tail energy and sub-bandgap photo response spectroscopy of the alloy film were investigated. The film quality of the alloy deposited with hydrogen dilution is greatly improved comparing to that of the alloy film deposited without hydrogen dilution. The electron spin resonance experiment shows that selenium atom is a good dangling bond terminator.
Deposition of Fluorinated Silicon Nitride using Plasma Enhanced Chemical Vapor Deposition Technique
Authors: Khan Ibrahim , Naseem H. A. , Ang S. S. , Brown W. D. 
Published: March 2011

ABSTRACTHigh hydrogen content of ammonia/silane deposited silicon nitride films has been linked to instability in electronic devices such as MOSFET's MNOSFET's and TFT's. Fluorine has been proposed to help reduce the hydrogen content of these films. In this work, NF3 was used as a fluorinating agent. Optical and electrical properties were studied as a function of NF3 flow rate. A maximum optical gap of 5.3 eV was obtained with NF3 as compared to 3.2 eV without. The dielectric strength improved from 4 to 10 MV/cm with the addition of NF3. FTIR data show that the Si-N peak shifts to higher wave numbers and the Si-H peak drops below the detection limit with the addition of NF3. Also, the broad Si-N peak at 850 cm-1 is composed of many individual peaks which become discernable when a stainless steel screen is placed in front of the substrate. As the NF3 concentration is increased, a new peak at 1030–1060 cm-1 appears. This may be associated with a N-F vibration (1030 cm-1).
Effects of Hydrogen Radical Annealing on Electrical Properties of Amorphous Silicon
Authors: Jang Jin , Kim Tae Gon , Koh Song Ok , Song Hyon Kyun , Park Kyu Chang , Chung Moon Hyun , Kim Sung Chul 
Published: March 2011

ABSTRACTWe studied the layer by layer deposition technique of a-Si:H film, where the hydrogen radicals are exposed between the deposition of each layer. The effects of each layer thickness and hydrogen radical exposure time on the electrical and optical properties were studied. With the decrease of the each layer thickness, more hydrogen is involved in the network if the structure is still amorphous, but the hydrogen content is very small for microcrystal Si formed by long exposure to hydrogen radicals in between the depositions of thin layers.
a-SiC:H Doped with Reactive Gases and with Ion Implantation
Authors: Demichelis F. , Pirri C. F. , Tresso E. , Della Mea G. , Rigato V. , Rava P. , Amato G. 
Published: March 2011

ABSTRACTBoron doped a-SiC:H samples have been obtained both by gas phase doping during film growth and by using ion implantation. All the implanted samples were annealed under vacuum to remove the damage introduced by ion implantation and to produce a dopant diffusion. Physical properties deduced by optical, electrical and structural characterization of the two sets of samples have been compared. Ion implantation technique allows a better control of the dopant dose but increases the compositional disorder and the obtained conductivity values are one order of magnitude lower than those of gas doped samples.
Etching Properties of Hydrogenated Amorphous Silicon
Authors: Tsuo Y. S. , Xu Y. , Baker D. W. , Deb S.K 
Published: March 2011

ABSTRACTWe have studied wet-chemical and dry etching properties of doped and undoped hydrogenated amorphous silicon (a-Si:H) films with bonded hydrogen content varying from 0 to 20 at.%. Etching processes studied include (1) wet-chemical etching using solutions of KOH, isopropyl alcohol (IPA), and H2O, (2) hydrogen plasma etching, and (3) XeF2 vapor etching.
The Slope Etching of a-Si:H Film using CF4 + O2 Gas
Authors: Sung Kang Hyun , Park B. W. , Kim J. J. , Kim C. Y. , Choi J. I. , Bae H. K. , Park Y. H. , Hur C. W. 
Published: March 2011

ABSTRACTThe slope etching technology of hydrogenated amorphous silicon film (a-Si:H) has been very useful for its devices; thin film transistor, contact image sensor and other large area electronic components. To obtain a good step coverage slope etching was performed by RIE using CF4 gas and optimum amount of O2 gas after modification of photoresist(PR) patterns by thermal treatment. In this experiment, primary factors were1) thermal treatment temperature and time of PR.2) CF4 gas flow rate, etch rate of a-Si:H film and ash rate of PR in proportion to O2 gas flow rate.As a result, the slope angle of 11° was obtained when CF4 gas flow rate was 46 SCCM, O2 gas flow rate was 7 SCCM and thermal treatment temperature and time was 140°C and 30 minutes respectively.
Propagating Shear Waves in Liquid Pentachlorobiphenyl
Authors: Bezot P. , Hesse-Bezot C. , Pruzan P. 
Published: March 2011

ABSTRACTA depolarized light scattering study of pressure supercooled Pentachlorobiphenyl is presented. Fram the analysis of propa gative depolarized shear doublets, the shear modulus G∞ at infinite frequency is measured for various temperatures. The pressure range is from atmospheric pressure to pressures whem the liquid is in a glassy state : G∞ (p) is found to vary linearly at each measured temperature.
Fatigue Crack Growth in Autofrettaged Thick-Walled High Pressure Tube Material
Authors: Stacey A. , Webster G.A. 
Published: March 2011

ABSTRACTFatigue crack growth studies have been made on C-shaped and ring specimens taken from as-received and autofrettaged 4333 M4 thick-walled tubing. The ring specimen was chosen because it enables cracks to be propagated through the same residual stress distribution as that present in the tubing. It is shown that the reduced crack growth rates measured close to the bore in autofrettaged tubing can be attributed to the presence of compressive residual stresses there and can be explained in terms of the contribution of these stresses to the stress intensity factor range applied.
On the Determination of Stress Intensity Factors for Cracked Thick Cylinders
Authors: Parker A P , Andrasic C P 
Published: March 2011

ABSTRACTThe authors have previously published stress intensity (K) solutions for singly and multiply cracked thick cylinders with internal pressure and autofrettage stress fields. In this paper a method of obtaining K values for intermediate radii ratios is proposed. The method involves an approximate superposition procedure which models the removal (or addition) of cylinder material and is based on the nearest available radii ratio. The procedure is exact for very short crack lengths, and generally gives answers within 5% at crack lengths up to 20% of wall thickness (wherein most of the fatigue lifetime is expended) after removal of 20% of the wall thickness. A simple expression is given for the anticipated change in fatigue lifetime resulting from material removal.
Two-Parameter Semiconductor Transducer for Measuring High-Pressure and Temperature
Authors: Wlodarski W. 
Published: March 2011

ABSTRACTThe paper presents the results of studies on the application of semiconductor p-n junctions as two-parameter transducers of high-hydrostatic pressure and of temperature in the area of the pressure. A block diagram of an electronic circuit intended to collaborate with a two-parameter transducer has been given.
Design of Blind End Closures for High Pressure Vessels
Authors: Chaaban A. , Leung K. , Pick R. J. , Burns D. J. 
Published: March 2011

ABSTRACTThe finite element method has been used to investigate the stress fields in blind end closures of thick-walled pressure vessels. A design curve for choosing end thickness has been developed by elastic analysis of a range of geometries and by elastic-plastic analysis of several geometries. The effects of inner corner radius of the blind end and a small
central hole in the end are discussed.
The Growth Rate of Semi-Elliptic Fatigue Cracks in Thick-Walled Cylinders
Authors: Lees W. A. , Crofton P. S. J. 
Published: March 2011

ABSTRACTThe rate of growth of fatigue cracks originating at the bore and at the outside surface of thick-walled low alloy steel cylinders has been measured for cylinders subjected to fluctuating internal pressure.Analysis of the results using linear elastic fracture mechanics relationships shows that crack growth rates found in air adequately predict the behaviour of cracks growing from the outside surface of a cylinder.Fatigue cracks growing from the bore of a cylinder subjected to fluctuating internal pressure are found to advance at a consistently higher rate than that predicted from crack growth rate tests carried out in air.These findings are discussed in relation to the proposed adoption of existent strain-life fatigue data for pressure vessel design.
Effect of Hydrostatic Pressure on Geometry of Slip in Silicon Iron Single Crystals
Authors: Dobromyslov A.V. , Dolgikh G.V. , Talutz N.I. , Shmatov V.T. , Beresnev B. I. 
Published: March 2011

ABSTRACTThe effect of the pressure 550MPa on the choice of the acting slip plane in the single crystals of Fe−2,9%Si was studied. It was established that the presence of pressure resulted in the increase of the slip asymmetry. The effect of pressure is attributed to the action of normal stresses and to the special structure of screw dislocations.
Study on Taylor Criterion for Complete Fracture of the Casing Packed with High Explosive
Authors: Danian Chen , Desheng Wang 
Published: March 2011

ABSTRACTThe criterion for complete fracture of the casing by detonation of packed high explosive was first presented by G.I.Taylor. Thereafter Taylor criterion has been reviewed and extended by many authors. This paper is intended to present a clear understanding of the fragmentation mechanism, and to study the influence of stress waves on the fracture of the casing using finite difference calculation of elastic-plastic flow. The results show that Taylor criterion is correct to a certain extent.
Equation of State of Helium and Polybutene and Raman Spectrum of Water at High Shock Pressures and Temperatures
Authors: Nellis W. J. , Holmes N. C. , Mitchell A. C. , Trainor R. J. , Boslough M. B. , Ree F. H. , Walrafen G. E. 
Published: March 2011

ABSTRACTLiquid helium was shock-compressed in Hugoniot equation-of-state measurements at pressures of 1.2 and 16 GPa (12 and 160 kbar) using a two-stage light-gas gun [1]. Specimens were initially at a temperature of 4.3 K and a molar volume of 32 cm3/mole. Specimen holders were a refinement of the cryogenic targets used for liquid H2 and D2 experiments [2]. The data are in good agreement with the published theoretical prediction of Young, et al.[3] The high shock temperatures test the repulsive pair potential to an interatomic spacing approaching 1 Å, which is comparable to a solid volume at a temperature of 0 K of about 0.5 cm3/mole.
Measurement of Liquid Compressibility in a Gasketed Diamond Anvil Cell by a Modified Piston-Displacement Method
Authors: Chang-Sheng Zha 
Published: March 2011

ABSTRACTThe compressibility of liquids was measured in a gasketed diamond anvil cell using a modified piston displacement method. A pair of metal markers was fixed on the diamonds. The gasket thickness at different pressures was measured by monitoring the distance change between the markers using a micrometer microscope. The area of the gasket hole was measured by means of microphotography. Then the product of the average area and thickness of the gasket hole determined the sample volume. Using this method we obtained the compressibility of a 4:1 v/v methanol-ethanol liquid mixture at hydrostatic pressures up to 8 GPa and found that the liquid volume at 8 GPa decreases to 51.5% of the initial volume. By the least-squares method, we fitted the experimental data to the Tait equation and obtained C=0.4055, B=0.5436 GPa. The relative error is estimated to be about 1.7%. This simple and convenient method could significantly extend the pressure range of liquid compressibility measurements.
Surface Accumulation of Boron During Si Molecular Beam Epitaxy
Authors: Parry C. P. , Kubiak R. A. A. , Newstead S. M. , Parker E. H. C. , Whall T. E. 
Published: March 2011

ABSTRACTA high temperature, elemental boron evaporation source has been used for the study of the boron doping behaviour in Si as a function of growth temperature and doping level. Significant profile smearing of boron at doping levels below 5×1018cm−3 is observed. Profile smearing is more severe in higher doped samples for growth temperatures above 600°C at a growth rate of 0.28 nms−1. This is interpreted as arising from the formation of a surface phase of boron at higher doping levels. The marked improvement in profile abruptness at low temperatures suggests significant benefits associated with the use of an elemental boron source for the growth of high resolution Si/Si1−xGex device structures.
X-Ray Characterisation of Boron Delta Layers in Si and SiGe
Authors: Powell A. R. , Kubiak R. A. , Whall T. E. , Parker E. H. C. , Bowen D. K. 
Published: March 2011

ABSTRACTWe demonstrate the growth, by MBE, of high sheet density B delta layers in both Si and SiGe epitaxial layers. Double Crystal X-Ray Diffraction is shown to be a non-destructive method of characterising the width of very narrow (0.3 nm) delta layers and the sheet density of the activated B. The ability of delta layers to withstand high temperature anneals is considered and it is found that a 750 °C anneal for 1 hour broadens the delta layer to beyond the width required for carrier confinement.