bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photoconductivity Decay in Amorphous Semiconductors
Authors: Pickin William , Mendoza Doroteo , Alonso Juan Carlos 
Published: March 2011

AbstractBased on modifications of the standard multiple trapping approach we present a theory of photoconductivity decay from the steady state in which explicit account is taken of the minority carrier behaviour. We use this to develop a physical understanding of the decay process. We obtain the intensity dependence of the decay time and compare it with experimental results for hydrogenated amorphous silicon.
Amorphous Silicon Deposition Diagnostics Using Coherent Anti-Stokes Raman Spectroscopy
Authors: Shing Y. H. , Perry J. W. , Coulter D. R. , Radhakrishnan G. 
Published: March 2011

AbstractIn situ process diagnostics using coherent anti-Stokes Raman spectroscopy (CARS) have been performed under state-of-the-art a-Si:H film deposition conditions in a reactor designed for a-Si:H solar cell fabrication. The silane plasma of device-quality a-Si:H film depositions was monitored by measuring the silane ν1 band CARS spectrum to determine the depletion induced by the RF glow discharge. The silane depletion is linearly dependent on the RF power in the region of 4 to 12 W with a slope of O.5%/mWcm−2. The depletion is also dependent on the SiH4 flow rate starting with a 50% depletion at a low flow rate of 5.6 sccm and asymptotically approaching an 8% depletion at a high flow rate of 80 sccm. The a-Si:H film deposition rate is systematically measured as a function of the flow rate and the RF power. Linear correlations between the silane depletion and the film deposition rate are observed. The results are discussed in terms of primary electron impact dissociations of silane and the residence time of SiH4 molecule in the glow discharge region.
Deposition of a-SiNx Films by ArF Laser Induced CVD as Diagnosed by Optical Emission Spectroscopy
Authors: Nishikawa S. , Matsuhashi H. , Ishida T. , Ohno S. , Ushio S. 
Published: March 2011

AbstractDeposition of SiNx films by ArF laser induced chemical vapor deposition has been investigated. The films exhibit excellent electrical properties; the high breakdown voltage and the low fixed charge are the same as in films deposited by LPCVD, but the BHF etching rate of them is larger by a factor about 4 than that prepared by the plasma CVD. The diffusion length of the radicals contributing to the deposition was estimated from the distribution of the deposition rate as a function of the deposition parameters. The optical emission from the radicals produced by ArF laser irradiation was also studied. Using these results, we discuss the mechanism of the deposition.
IR-Spectroscopy and Electronic Properties of RF Magnetron Sputtered a-SiA:H (A=C,Ge) Films
Authors: Rubel H. , Schröder B. 
Published: March 2011

Abstracta-S1−xCx:H and a-Si1− Ge :H films are prepared by magnetron sputtering in an argon-hydrogen-methane/germane atmosphere. The hydrogen content of the carbon alloy increases with x, saturating near 40 at% for the maximum C-content (x = 0.88). From a detailed analysis of the infrared absorption modes we conclude that the formation of (CHm)n C/Si-groups (n = 1,2,3, m = 2,3) is responsible for the growth of hy r gen rich and inhomogeneous films. Structural, electrical and optical properties of the films show characteristic changes near an alloy composition of x = 0.5 which indicate the transition to a structure with threefold coordinated carbon. For the germanium alloy system lower DOS and improved photoelectrical properties have been measured for y ≤ 0.01. Decreasing H-content and SiH2 /GeH2 bonding configurations impair the alloy properties for higher y.
Recombination and Electronic Transport in Low-Gap a-Si,Ge:H,F Alloys
Authors: Aljishi S. , Shen D. S. , Chu V. , Smith Z E. , Conde J. P. , Kolodzey J. , Slobodin D. , Wagner S. 
Published: March 2011

AbstractWe have studied the temperature and intensity dependence (130K to 300K) of photo- and dark conductivity in a series of low-gap a-Si,Ge:H,F alloys (Eopt=1.25 to 1.33 eV) prepared under different deposition conditions. Electron time of flight experiments were conducted between 300K and 400K. Results reveal an increase in the slope of the exponential conduction band tail to ∼ 50 meV and a peak in electron trapping states at 0.3 to 0.4 eV below the conduction band edge, leading to a transition from extended to hopping conduction by electrons at slightly below room temperature. The alloys have midgap defect densities in the low 1017 cm−3eV−1 range.
Estimation of Defect State Densities from Bulk Photoelectronic Properties of a-Si,Ge:H Alloys
Authors: Parsons G. N. , Lucovsky G. 
Published: March 2011

AbstractWe have studied the photoelectronic properities of a- Si(x),Ge(1−x):H alloy films and have concluded that there are depletion layers at the film surface and film/oxide interface that effect the determination of bulk quantum effieciencymobility- lifetime (nuT) products. From changes in dark conductivity activation energy with film thickness and the nuT product with wavelength of incident light we have estimated defeci sta:e lensitles. Our best x=0.5 film has an nuT value of 9×10−8 cm2 V−1 andaj defect state density near the Fermi level of approximately 5×10 cm−3 eV−1.
Schottky Barriers on a-Si:H,F/a-Si,Ge:H,F Superlattices
Authors: Chu V. , Conde J. P. , Aljishi S. , Shen D. S. , Smith Z E. , Wagner S. 
Published: March 2011

AbstractWe report measurements of Schottky barrier heights and minority carrier mobilitylifetime products of multilayer structures composed of a-Si:H,F and a-Si,Ge:H,F. These layers are grown by r.f. glow discharge decompostion of SiF4, GeF4, and H2 in the a-Si,Ge:H,F (well) layer and of SiF4 and H2 in the a-Si:H,F (barrier) layer.Schottky barrier height ΦB of Pt is measured using internal photoemission measurements. The minority carrier mobility-lifetime product (μτ)p is extracted from a fit of the voltage dependence of internal quantum efficiency to the Hecht expression. Both ΦB and (μτ)p are measured as a function of barrier and well thicknesses.
Determination of the Density of Gap States in a-Si:H from Studies of Semiconductor/Oxide Multilayer Films
Authors: Jones R. B. , Moddel G. 
Published: March 2011

AbstractA method for determining the density of states [N(E)] in the upper half of the energy gap in hydrogenated amorphous silicon (a-Si:H) is proposed and experimental results are simulated. The method involves the growth and measurement of the planar conductivity in multilayer films in which each layer is separated by a thermally grown oxide. Band-bending occurs at each interface throughout the film thickness. The conductivity parallel to the layers in the films is a function of the band-bending, which in turn depends on N(E), in the energy range through which the Fermi level is shifted. Computer simulations of the oxide-induced band-bending have been used to generate curves of the conductivity as a function of layer-thickness for various N(E). By matching experimental results with the simulation curves, the N(E) may be deduced. The simulations have also been used to show the difference between the bulk conductivity activation energy and effective activation energy which is measured in films influenced by a surface oxide.
a-Si MOS Fet with Native-Oxide Gate Grown by Normal-Pressure and Low-Temperature Thermal-Oxidation Method
Authors: Zhang Hong-Yong , Matsumura Masakiyo 
Published: March 2011

AbstractNative silicon-dioxide film has been grown thermally under normalpressure and low-temperature conditions, and applied to a gate insulator of amorphous-silicon thin-film transistors. Th highest field-effect mobility under room-temperature conditions was 0.7cm2/Vs. Temperature dependence of the transistor characteristics has also been studied. The transistor has been operated in a wide temperature range from -196 °C to more than 200°C with satisfactorily stable manner. Characteristic temperature of the localized state density distribution has been estimated to be about 20° C.
Physics of High Efficiency Multijunction Solar Cells
Authors: Yang Jeffrey , Ross Robert , Mohr Ralph , Fournier Jeffrey P. 
Published: March 2011

AbstractWe have shown that high efficiency solar cells can be obtained by incorporating materials of different band gaps in a multijunction configuration. This configuration gives rise to high efficiency due to spectrum splitting as well as superior stability due to thin top cells.We have fabricated multijunction solar cells and acheived a 13% conversion efficiency using 1.7eV a-Si:F:H and 1.5 eV a-Si:Ge:F:H materials in a three-cell triple configuration. This device was deposited onto a stainless steel substrate coated with a back reflector; it also incorporates a microcrystalline p+ layer.The physical properties of each of the solar cell layers and their role in the device physics of a high efficiency solar cell will be described.
“Stable” Defects as, Metastable Defects in a-Si:H
Authors: Redfield David 
Published: March 2011

AbstractAn expanded kinetic description of formation and anneal of metastable defects (MSDs) in a-Si:H shows that (1)the apparently “stable” defects are just a statistical subset of the total density of potential MSD sites; (2)the temperature dependence of the saturation density of MSDs has three distinct regions that have not been recognized; (3)the effects of doping in increasing both the density of “stable” defects and the sensitivity to light are readily explained by an increase in the density of total potential defect sites, not just defects; (4)the defects in good undoped material are chemical in origin, not intrinsic to the disordered state of the material.
Changes of IR Vibrational Absorption by Light Soaking in Hydrogenated Amorphous Silicon
Authors: Jang Jin , Park Seung Chul , Lee Chang Geun , Kim Sung Chul , Lee Choochon , Yoon Jung Kee 
Published: March 2011

AbstractLight-induced changes in vibrational absorption of SiHn have been studied for a-Si:H films. The stretching mode absorption near 2000 cm−1 decreases after light exposure. The magnitude of the change increases as the substrate temperature is lowered, and little change is observed for a-Si:H films deposited above 200°C. From the changes both for the peak and the spectrum, it is suggested that the hydrogen in the bulk diffuses to the microvoids, where it can combine to form H2 in low substrate temperature sample. The B-H modes increase after light soaking, Which is related with the increase in doping efficiency of boron, which is confirmed from the conductivity change with time during illumination.
Light-Induced Degradation and Annealing Behaviour of Amorphous Silicon: A Comparison of Films and Devices
Authors: Bennett M. S. , Wiedeman S. , Rajan K. , Smoot M. 
Published: March 2011

AbstractThe kinetics of the Staebler-Wronski effect in a-Si:H p-i-n solar cells are well known [1]. We report measurements of the kinetics of light-induced degradation and annealing of a-Si films in which we have monitored the changes in subgap absorption by means of photothermal deflection spectroscopy (PDS). The kinetics of films and cells are found to be very similar, suggesting that cell degradation is largely a material, as opposed to a device effect.
A High Speed High Resolution Contact Line Imager Using Amorphous Silicon Alloy Pin Diodes
Authors: Swartz L. , Kitamura K. , Vijan M. , McGill J. , Cannella V. , Yaniv Z. 
Published: March 2011

AbstractWe report the development of a very high speed high resolution contact line imager using amorphous silicon alloy PIN diodes both as photosensing elements and as isolation diodes in the multiplexing scheme. High speed is achieved by reading the integrated photocurrent in 8μsec and using current integration times less than Imsec. For 200 dots/inch, the scan speed at an illumination of 5×10−4W/cm2 is over 1000 lines/sec. This allows the reading of an A4 (8½″×11″) page in less than 2.0 sec. At this light level, the signal to noise ratio is greater than 40dB. The photosensor array can be used in the true direct contact mode and the multiplexed addressing scheme gives a substantial reduction in the number of peripheral IC chips necessary for operation.
Capacitance Studies of Ion-Implanted N-Type Hydrogenatfd Amdrphous Silicon
Authors: Michelson C. E. , Cohen J. D. , Harbison J. P. 
Published: March 2011

AbstractThe effect of the implantation of oxygen ions on the density of states in the mobility gap of n type hydrogenated amorphous silicon (a-Si:H) is studied using drive-level capacitance profiling, deep-level transient spectroscopy( DLTS), and transient voltage-pulse photocapacitance. After implantation, we observe a broadening of both the conduction and valence band tails and an increase in the dangling bond density near midgap, as well as a shift of the Fermi level toward midgap by approximately 100 meV in two out of the throe films studied. We also observed the addition of a distinct defect band at approximately 0.7 eV below the conduction nd mobility edge in films implanted with oxygen doses greater than 1012 cm−2.
Chemical Vapor Deposited Boron Carbide: Growth by a Vapor-Liquidsolid Process
Authors: Mackinnon Ian D. R. , Smith Katherine L. 
Published: March 2011

ABSTRACTDetailed analytical electron microscope (AEM) studies of yellow whiskers produced by chemical vapor deposition (CVD)1 show that two basic types of whiskers are produced at low temperatures (between 1200°C and 1400°C) and low boron to carbon gas ratios. Both whisker types show planar microstructures such as twin planes and stacking faults oriented parallel to, or at a rhombohedral angle to, the growth direction. For both whisker types, the presence of droplet-like terminations containing both Si and Ni indicate that the growth process during CVD is via a vapor-liquid-solid (VLS) mechanism.
β-SiC MESFETs
Authors: Kelner G. , Binari S. , Sleger K. , Kong H. 
Published: March 2011

ABSTRACTA β-SiC MESFET structure with functional DC characteristics has been fabricated and evaluated. The MESFET employs an epitaxial n on p SiC layer grown by chemical vapor deposition on a p-type Si(100) substrate. Modulation of the n-type channel current is achieved with a Au Schottky barrier gate. A transconductance of 2.3 mS/mm was obtained using a 5 micron gate length.
Synthetic Diamond, Its Properties and Synthesis
Authors: Yoder Max N. 
Published: March 2011

ABSTRACTThe synthesis of crystalline diamond in the Soviet Union, Japan, and the United States is reviewed. A comparison of the various growth techniques is presented. Hydrogen and its role in the synthesis process has been controversial; a model is presented illustrating its essential, but limited role. Another controversial aspect of diamond synthesis concerns the nature of the carbon bond in the reactant gas and how this influences the resultant crystal; an heuristic model is provided. Non-thermal equilibrium growth techniques are generic to the recent advances in diamond growth; the separation of the process for the disassociation of the reactant gas from that of the “surface cleaning” and the artificial stimulation of the surface migration velocity may be absolutely necessary for defect-free nucleation and growth. While the various properties of diamond have been known long before the advent of artifact diamond, its potential for use in devices has only recently been modelled and calculated; numerical figures of merit are compared with those of other semiconducting materials. Charge carrier velocity profiles of diamond are compared with those of more conventional semiconductors. Strengths and weaknesses accruing from the diamond velocity profile are addressed.
Electronic Structure of Boron and Boron-Rich Borides
Authors: Switendick Alfred C. 
Published: March 2011

ABSTRACTI have calculated the electronic structure of cubic B12 and B12 P2 using the linear augmented plane wave method. These calculations are selfconsistent and include calculation of the total energy. Within the strict muffin tin approximation (spheres centered only on atomic positionsconstant potential otherwise) these systems are unbound with respect to the atomic constituents. Using interstitial spheres, up to 77% of the unit cell can easily be filled to yield much more reasonable total energies. Although the improvement in the total energy is significant upon including the interstitial spheres, the band structure and densities of states are not significantly changed. Similarly, the real atomic charge distributions (B, P) are little changed, while the interstitial distribution does change to reflect the additional freedom provided by the interstitial spheres. Results including the rhombohedral and icosohedral distortions in both systems are discussed. Gaps are found to open up in the alpha rhombohedral boron and in the B12 P2 systems as are observed experimentally.
Characterization of Plasma-Deposited Amorphous Carbon Films
Authors: Hsu Wen. L. , Foltz G. W. , Greulich F. A. , Mccarty K. F. , Thomas G. J. , Green P. F. , Doyle B. L. 
Published: March 2011

ABSTRACTThin carbon films of ˜ 600 Å have been deposited on Si <111> wafers by striking an RF discharge in gas mixtures of hydrogen and methane. The deposition rate increased with increasing methane fraction. The peak rate was ˜ 1 Å/sec at an applied power density of 0.4 W cm−2. The films, with an average density of 2.54 gm cm−3, are amorphous in nature but exhibit broad diffraction maxima corresponding to interatcidc spacings of 2.05Å and 1. 15Å. Measurements of hydrogen concentration in the films showed that the hydrogen at. % [H/(H+C)] increased from 30 to 40% as the hydrogen fraction in the feed gas increased. By using a D2-CH4, we were also able to deduce that hydrogen molecules can be a large source of hydrogen trapped in the films.
Laser/Optical Diagnostic Techniques for Plasma Materials Processing
Authors: Roman Ward C. 
Published: March 2011

ABSTRACTThe application of plasma techniques is emerging as one of the more efficient means of processing materials. Technology transfer of plasma systems, both thermal and nonequilibrium, however, is severely limited by a lack of understanding of the basic mechanisms involved which govern the plasma processes used in many applications including advanced coatings. The aspects of plasma gas temperature, and species concentration and distribution (molecular, atomic, excited) in the gas phase and associated synergistic effects are fragmentary and unclear. Laser/optical diagnostic techniques represent a critical starting point for providing this needed information; they are in-situ, non-intrusive,species and quantum level specific and give excellent spatial and temporal resolution. A survey of Laser/optical diagnostic techniques applicable to plasma materials processing needs is presented. Some examples of the use of different techniques are also given.
An Experimental Method for Species Concentration Measurements in a Welding ARC Using Laser-Induced Fluorescence
Authors: Snyder S. C. , Shaw C. B. , Shull C. L. 
Published: March 2011

ABSTRACTAn experimental method using laser-induced fluorescence (LIF) to determine the distribution of neutral manganese in a gas tungsten welding arc is described. The theoretical consideration and experimental difficulties encountered when extending LIF techniques from flames to thermal plasmas are discussed, and preliminary results are presented.
Plasma Chemical Aspects of Magnetron Ion Etching with CF4/O2 and CF4/H2
Authors: Bright A. A. , Kaushik S. , Oehrlein G. S. 
Published: March 2011

ABSTRACTMagnetron plasmas are of great current interest for semiconductor manufacturing applications because of their high ion density and low operating pressure. We have studied the properties of a magnetron ion etching system using CF4, CF4/O2, and CF4/H2 with respect to the plasma chemistry and the interaction of the plasma with the etched substrate. The higher dissociation and ionization rates lead to significant changes in the species present in the plasma as compared to a conventional reactive ion etching (RIE) plasma. The F atom concentration in a CF4 magnetron plasma is much higher than in a RIE plasma. The addition of O2 leads to only a small further enhancement and produces a decrease in the Si etch rate. Addition of H2 suppresses the F atom concentration slightly, produces very little C-F polymer, and does not lead to highly selective etching of SiO2 over Si. The highly dissociated species in the magnetron plasma produce less C-F polymer, both on the wafer and on the chamber walls, relative to RIE.
A New Method for Real-Time Plasma Etch Process Control: Correlation of Contact Resistance with Nondestructive Modulated Reflectance
Authors: Malazgirt Alp , Smith W. Lee 
Published: March 2011

ABSTRACTWe have established a correlation between contact resistance, measured on VLSI MOS integrated circuits at final electrical test, with thermal wave modulated reflectance signal measured just after the metal contact hole etch process. This correlation exists because etching past the time that a particular contact hole is cleared of oxide (i.e., overetching) causes (a) a thinning of the underlying shallow ion-implanted low-resistivity silicon layer with a resulting increase in the contact resistance, and (b) damage to the silicon. Damape was measured on the actual product wafers with the thermal wave modulated reflectance method employing low-power laser beams in a noncontact, nondestructive manner. Hence, the thermal wave measurements of damage make it possible to monitor the etch processing on the product wafers.Our results show monotonic increases in both the damage (mod. reflec. from 30 to 260 units) and contact resistance (from 40 to 180 ohms/contact) with overetch time up to 1.5 min., at which point polymer deposition alters the dependence by screening the silicon surface. We show results obtained for three categories of VLSI devices (SRAM, PROM, FIFO), and report on the advantages and limitations of this new method for realtime plasma etch inspection.
The Influence of Magnetic Fields on the Properties of Amorphous Carbon Prepared by Plasma Deposition
Authors: Jarman R. H. , Howe A. T. 
Published: March 2011

ABSTRACTAmorphous carbon films exhibit a wide range of optical, electrical and mechanical properties which make them candidates for a number of applications such as protective coatings and insulators in electronic devices. We describe the effects of a magnetic field applied at the powered electrode in a capacitively coupled rf discharge on the optical and electrical properties of amorphous carbon films deposited on substrates mounted on both electrodes. In the case of substrates placed on the powered electrode, the film properties appear to be very sensitive to the magnetic field strength. At the highest magnetic field, the deposition rates are very much higher than those obtained in the absence of a magnetic field. The optical gap varies from 1.1 eV to 2.7 eV depending on the deposition conditions. The electrical conductivities of the films are very low and show a complex dependence on the applied electric field.
Bonded Hydrogen in Silicon Oxide Thin Films Deposited By Remote Plasma Enhanced Chemical Vapor Deposition
Authors: Tsu D. V. , Lucovsky G. 
Published: March 2011

ABSTRACTWe have deposited a range of silicon oxides by the Remote Plasma Enhanced CVD method. By varying gas mixtures and/or substrate temperature, it is possible to deposit films that are essentially stoichiometric SiO_, Si-deficient oxides which have OH groups but no SiH and Si-rich oxides which have SiH groups and no OH. This paper addresses three issues : (1) the nature of the infrared vibrations associated with the SiH and SiOH groups; (2) the use of D for H substitutions to study the vibrations in (1); and (3) the chemical origin of the SiOH group in the Si-deficient films.