bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characteristics of Materials Produced by Plasma Treatment of Radioactive Wastes
Authors: Hoffelner W. , Haefeli V. , Burkhard R. 
Published: April 2011

ABSTRACTPlasma processes become more and more attractive for the treatment of radioactive low/medium level waste. Plants with throughput rates ranging from 20 kilograms to several hundred kilograms per hour are under construction or under evaluation in different countries. One major installation is under construction at the ZWILAG-site in Wurenlingen (Switzerland). ZWILAG (Zwischenlager Wurenlingen AG) is a company being responsible for treatment and intermediate storage of all radioactive wastes occurring in Switzerland. Thermal destruction (pyrolysis) of organic material and melting of the inorganic residuals and inorganic feed stock can be done simultaneously in a plasma heated vessel. The following output materials are obtained: Metal, glassy slag, off-gas. Depending on feed stock and storage requirements these outputs can have different properties. The distribution of the activity is of particular importance. Isotopes like cobalt-60 (as a metal) partition almost quantitatively to the metal phase. Volatile isotopes like cesium-137 partition to some extent to the off-gas, they can however be retained in the slag to a high extent by employing a two stage process. For some applications the activity in the metal can be kept below the activity tolerance limits making the metal suitable for even non nuclear applications. The most important property of the slag is its leaching behaviour. Mechanical properties can be of importance, too. The paper will present examples from different types of radioactive waste: typical low level mixed waste, ion exchange resins and zeolites, mixtures of concrete and metal, contaminated soil, material contaminated with natural activity and others. Composition of the materials, activity distributions, data on leaching behaviour and some mechanical properties are presented
Effects of Band Offsets on a-Sic:H/c-Si Heterojunction Solar Cell Performance
Authors: Cleef M. W. M. Van , Rubinelli F. A. , Schropp R. E. I. 
Published: April 2011

ABSTRACTWe used the internal photoemission technique to determine the exact valence and conduction band offsets at the a-SiC:H/c-Si interface and investigated with numerical simulations their effects on the photocarrier collection in p+a-SiC:H/n c-Si heterojunction solar cells. The valence and conduction band offsets were found to be 0.60 eV and 0.55 eV, respectively. Simulation results show that a high valence band offset increases the open circuit voltage (higher built-in potential) but on the other hand can decrease the fill factor (by blocking the collection of photogenerated holes at the front contact). Interestingly, despite having a large barrier inside the valence band (ΔEv = 0.6 eV), our highly doped p+a-SiC:H/n c-Si heterojunction solar cells show no collection problems (FF= 0.73). Both IPE measurements and simulation results indicate that tunneling of holes through this barrier in the valence band can explain this effect. For thin highly doped (Eact = 0.33 eV) p+a-SiC:H layers, the tunnel barrier becomes very narrow (< 70 Å) and the tunneling probability is strongly enhanced.
Stable Solar Cells Prepared from Dichlorosilane
Authors: Yamamoto Y. , Futako W. , Fukutani K. , Hagino M. , Sugawara T. , Kamiya T. , Fortmann C.M. , Shimizu I. 
Published: April 2011

ABSTRACTAmorphous silicon films and solar cell i-layers were prepared from dichlorosilane(DCS) by ECR- and VHF-CVD. The hydrogen content, the chlorine content and the band gap could be controlled by varying argon and hydrogen dilution. The interaction of energetic and reactive plasma species with substrates and other previously deposited layers was studied. DCS, ECR-CVD causes darkening of TCO substrates even when buffer layers and/or doped layers were previously deposited by RF-CVD. Therefore n-i-p solar cell structures were prepared on NiCr and subsequent p-i-n solar cells were prepared with VHF-CVD which did not causeTCO reduction or other reactions in previously deposited amorphous layers. Preliminary results indicate that the VHF-CVD solar cells are at least as stable as standard amorphous silicon solar cells.
Narrow Band Gap Amorphous Silicon-Based Solar Cells Prepared by High Temperature Processing
Authors: Kambe M. , Yamamoto Y. , Fukutani K. , Kamiya T. , Fortmann C.M. , Shimizu I. 
Published: April 2011

ABSTRACTGenerally higher depositions temperatures are required to prepare solar cells with narrow band gap amorphous silicon intrinsic layers. High processing temperatures require that diffusion resistant substrates and doped layer materials be developed. In the case of p-i-n solar cells both a new Ga-doped ZnO and/or semi-transparent Cr over-coated standard commercially available TCO show increased resistance to high temperature processing and it is possible to prepare efficient solar cells on these substrates at temperatures over 280 C. In most amorphous silicon i-layer cases a-SiC:H p-layers offer better diffusion resistance than microcrystalline players. However, in the case of narrow band gap amorphous silicon prepared at high temperatures using the argon treatment process [2] micro-crystalline p-layers offer significantly improved solar cell performance. Another promising approach involves the n-i-p deposition sequence, however, this case too can suffer from diffusion related problems.
Extremely Narrow Band Gap,∼1·50Ev, Amorphous Silicon
Authors: Fukutani K. , Sugawara T. , Futako W , Kamiya T. , Fortmann C.M. , Shimizu I. 
Published: April 2011

ABSTRACTHydrogenated amorphous silicon (a-Si:H) films were prepared by a layer-by-layer (LBL) argon treatment technique. Thin amorphous silicon layers are first deposited and then treated by Ar. Thick films are built up by repeatedly the process many times. By reducing the deposition rate during deposition time (T, sec), a-Si:H with the gaps narrower than 1·55eV were prepared at substrate temperature lower than 300°C. These narrow-gap films contained less than 2 at.% hydrogen and had rigid Si network. Also, these narrow gap films exhibited good light soaking stability.
Programmable 3-Dimensional Memories Based on Current Induced Conductivity in Hydrogenated Amorphous Silicon Nitride
Authors: Shannon J.M. , Lau S.P. , Sealy B.J. 
Published: April 2011

ABSTRACTChanges of several orders of magnitude in the low field conductivity of hydrogenated amorphous silicon alloy metal-semiconductor-metal MSM devices can be obtained by current stressing. This feature is suitable for memory applications, since the device can be programmed from an unstressed state to a stressed state with a ratio greater than 104. The change in conductivity is attributed to the creation of a large concentration of silicon dangling bond states during current stressing which form a defect band with a low activation energy for current transport. In this paper, we consider the use of current induced conductivity in hydrogenated amorphous silicon nitride (a-SiNx:H) multi-layer structures and show that, in principle, highly complex three dimensional circuits could be made. In particular, the potential of this approach is illustrated by using a simple MSMSM device with two silicon rich silicon nitride layers. An array with lxi0 elements has been fabricated and programmed to store 28 bits of binary information with three outputs per input.
Wide Band Gap a-Si:H Based Ihgh Gain Vidicon Devices Prepared by Chemical Anniealing
Authors: Futako W. , Sugawara T. , Kamiya T. , Fortmann C.M. , Shimizu I. 
Published: April 2011

ABSTRACTPreviously it was shown that high quality wide gap hydrogenated amorphous silicon material could be prepared by a layer-by-layer technique involving hydrogen chemical annealing. Using this wide gap material, high electric field, n-i-p diode devices were fabricated. Reverse bias dark current was suppressed by optimization of the n-layer doping level (250ppm) and the thickness (2000Å). Working vidicon type device were prepared, tested, and optimized by further reduction in the high reverse bias leakage current. Vidicon devices showed very promising performance; however, at the present stage of development some point defects were observable at the highest reverse bias voltages probed (∼-6×105 V/cm).
Nucleation of p-Type Microcrystalline Silicon on Amorphous Silicon for n-i-p Solar Cells Using B(CH3)3 And BF3 Dopant Source Gases
Authors: Koh Joohyun , Fujiwara H. , Koval R. J. , Wronski C. R. , Collins R. W. , Claflin B. , Lucovsky G. 
Published: April 2011

ABSTRACTReal time spectroscopic ellipsometry (RTSE) has been applied to identify optimal conditions for the nucleation and growth of 120 Å microcrystalline silicon (μc-Si:H) p-layers by rf plasma-enhanced chemical vapor deposition (PECVD) at 200°C on amorphous silicon (a-Si:H) i-layers in the n-i-p solar cell configuration. Analysis of the RTSE data provide the bulk p-layer dielectric function (2.5-4.3 eV), whose amplitude and shape yield insights into the structural quality and crystallinity of the p-layer. Among the deposition parameters varied include the underlying i-layer surface treatment, the p-layer plasma power flux, and the p-layer dopant source gas and flow ratio. Here we focus on the differences between p-layer deposition using trimethyl boron, B(CH3)3, and boron trifluoride, BF3, source gases. We find significant differences attributed to the differing effects of F and CH3radicals in the plasma on silicon crystallite growth.
Stability Improvement of a-Si:H Films Deposited in Sqwm-55 kHz Glow Discharge Plasma
Authors: Budaguan B.G. , Aivazov A.A. 
Published: April 2011

ABSTRACTIn this work we have used square-wave-modulated (SQWM) low frequency (55kHz) glow discharge plasma for deposition of a-Si:H films and observed a significant stability improvement. To investigate the origin of stability improvement the relation between growth mechanism, film microstructure and metastability was analyzed. It was shown that the use of SQWM-plasma decreases the concentration and average size of inhomogeneities calculated from AFM data while photoconductivity under He-Ne laser illumination (Staebler-Wronski effects) didn't degrade during standard time of experiments. Differential scanning calorimetry (DSC) measurements were carried out and it was found that in SQWM samples hydrogen effusion occurs at higher temperatures than in cw a-Si:H which is connected with increased structural stability of films deposited in SQWM-plasma. Taking into account the high photoconductivity and low defect density of SQWM samples it is concluded that modulating of LF plasma is a perspective method for deposition of stable a-Si:H films and its alloys.
Comparison of VHF, RF and Dc Plasma Excitation for a-Si:H Deposition with Hydrogen Dilution
Authors: Platz R. , Hof C. , Wieder S. , Rech B. , Fischer D. , Shah A. , Payne A. , Wagner S. 
Published: April 2011

ABSTRACTA comparative study of DC, RF and VHF excitation for the plasma enhanced chemical vapor deposition (PECVD) of intrinsic layers of a-Si:H is presented, with special emphasis on the effects of hydrogen dilution. Growth rates at comparable plasma power, for substrate temperatures between 100°C and 300°C and for various H2 dilution ratios are presented, along with optical bandgap, H content, and electronic transport properties in the light-soaked state.H2 strongly reduces the growth rate for all techniques. The growth rate for the highest H2 dilution ratio is approximately four times higher for VHF than for DC or RF excitation. In all three cases increasing the substrate temperature reduces the optical gap and the H content CH. Raising the substrate temperature slightly enhances the stability of undiluted films. H2 dilution increases the optical gap for all three techniques. The H content of RF- and VHF-deposited samples increases with increasing H2 dilution ratio, while in DC deposition it produces an initial drop of the H content, followed by an increase.In all three cases, H2 dilution improves the electronic transport properties of the material by roughly a factor of two. The gain in stability is most pronounced for relatively small dilution; in the case of DC deposition, too strong a dilution even has an adverse effect on stability.
Electrode Interdependence and Hole Capacitance in the Capacitance -Voltage Characteristics of Hydrogenated Amorphous Silicon Thin-Film Transistors
Authors: Park Hyuk-Ryeol , Cohen J. David 
Published: April 2011

ABSTRACTThe inter-electrode capacitance - voltage (C-V) characteristics of back-channel etched inverted-staggered hydrogenated amorphous silicon (a-Si:H) thin-film transistors (TFTs) were investigated. It is demonstrated that this simple measurement can be used to diagnose TFT parameters such as the fabricated channel length, the channel resistance, and the error in the mask alignment of the source and drain overlap lengths. The C-V characteristics associated with the hole accumulation in a-Si:H TFTs with n+-type source/drain contacts were also examined. We observed that the a.c. capacitance increases for low frequencies and/or moderately high measurement temperatures provided the gate voltage is sufficiently negative.
Microcrystalline Silicon-Germanium Alloys for Absorption Layers in Thin Film Solar Cells
Authors: Carius R. , Fölsch J. , Lundszien D. , Houben L. , Finger F. 
Published: April 2011

ABSTRACTThin microcrystalline silicon-germanium films (μ-Sil.xGex:H) prepared by PECVD at 95 MHz have been investigated. The optical absorption of these films increases in the infrared spectral region with increasing germanium content. In addition to the shift of the indirect gap an increase of the absorption coefficient above the band edge is observed. The material shows high crystallinity and exhibits good structural quality similar to pure μ-Si:H films. The films are homogeneous on a macroscopic to a microscopic scale as confirmed by Raman spectroscopy and Electron Microscopy methods. p-i-n solar cells with pc-Sil-xGex:H i-layers have been prepared for the first time. An efficiency of η = 3.1 % under AM1.5 has been obtained for a cell with 150 nm thin i-layer.
How do Impurities Affect the Growth of μc-Si:H?
Authors: Kamei Toshihiro , Fukawa Makoto , Nishimiya Tatsuyuki , Isomura Masao , Kondo Michio , Matsuda Akihisa , Claflin B. , Lucovsky G. 
Published: April 2011

ABSTRACTUltra clean plasma CVD process opens the doorway to clarify the role of impurities in the growth process of μc-Si:H. A reduction of impurity levels during the growth extends the temperature range for crystalline formation to lower side, i.e., high-crystallinity μc-Si:H formation even at room temperature, substantially reduces midgap defect density at 200°C, and enlarges crystalline grain size at 350°C. These results imply that impurities disrupt crystalline formation even on hydrogen covered surface. The crystalline-to-amorphous transition is induced by a loss of surface hydrogen coverage due to thermal hydrogen desorption at higher temperature of ∼450°C irrespective of the effect of oxygen impurity. Light-soaking experiments for the series of the films from a-Si:H to μc-Si:H films with different crystalline volume fraction indicate that the presence of small volume fraction of crystallite significantly suppresses light induced defect creation under the present light soaking condition of 3SUN 60°C 6hr. These results are explained in terms of preferential recombination of photo-excited carriers in the crystallite.
Hot-Wire CVD Poly-Silicon Films for Thin Film Devices
Authors: Rath J.K. , Tichelaar F.D. , Meiling H. , Schropp R.E.I. 
Published: April 2011

ABSTRACTSolar cell using profiled poly-Si:H by HWCVD as i-layer in the configuration SS/n-µSi:H(PECVD)/i-poly-Si:H(HWCVD)/p-µc-Si:H(PECVD)/ITO showed 3.7% efficiency. A current of 23.6 mA/cm2 was generated in only 1.5 µm thick poly-Si:H i-layer grown at ∼5Å/s. TFTs made with the poly-Si:H films (grown at ≥ 9Å/s) exhibited remarkable stability to long duration of 23 hours of gate bias stress of ∼lMV/cm. A saturation mobility of 1.5 cm2/Vs for the TFT has been achieved. Films made at low hydrogen dilution (Poly2) showed device quality (purely intrinsic nature, ambipolar diffusion length of 568 nm, only (220) oriented growth and low ESR defect density of <1017/cm3with complete absence of signal due to conduction electrons) but with an incubation phase of amorphous initial growth, whereas the films made at high hydrogen dilution (Polyl) had a polycrystalline initial growth, though with higher defect density, incorporated oxygen and randomly oriented grains. Poly2 films are compact and hydrogen bonding is at compact Si-H sites manifested as 2000 cm−1IR vibration and high temperature hydrogen evolution peak. Exchange interaction of spins and spin pairing are observed while increasing defects in such a compact structure. A new approach has been used to integrate these two regimes of growth to make profiled poly-Si:H layers. The new layers show good electronic properties as well as complete elimination of incubation phase.
Growth and Properties of Micro-Crystalline (Si,Ge):H Films
Authors: Erickson Karl , Dalal Vikram L. , Chumanov George 
Published: April 2011

ABSTRACTThis paper reports on the growth and characterization of micro-crystalline (Si,Ge) films deposited on glass and polyimide substrates. The films were grown using a hydrogen diluted remote ECR plasma process. The feedstock gases were silane and germane. The entire range of composition from 100% Si to 100% Ge was studied. A low-pressure, low-substrate temperature, and high-power environment was used to change the morphology from amorphous to micro-crystalline. The films deposited at 5 mT pressure are generally micro-crystalline. The film's structure was studied using Raman spectroscopy. Raman spectra show clear, sharp crystalline-type Si and Ge peaks. Electronic properties of the films, such as activation energy and absorption constant down to α = 1 cm−1 were also measured. The sub-gap absorption data also show crystalline absorption behavior, with the absorption shifting to lower energies as the Ge content is increased. This absorption data shows that the materials have low defect densities.
Novel Dichroic Polarizing Materials and Approaches to Large-Area Processing
Authors: Bobrov Yuri. A. , Casey Sean M. , Ignatov Leonid. Y. , Lazarev Pavel I. , Phillips Daniel , Tam-Chang Suk-Wah 
Published: April 2011

AbstractWe have developed new polarizing coating materials and processes which enable the fabrication of polarizers for large-area liquid-crystal displays. The polarizing materials are novel discotic surfactants which self-assemble in aqueous solutions to provide a stable liquid-crystalline phase within a wide range of concentrations and temperatures. These lyotropic liquid crystals in an aqueous medium can be spread on a substrate surface by a variety of techniques including a knife-like doctor blade, a rolling cylinder, or a roll-to-roll method. Under the shearing force applied during deposition, the liquid crystals align on the substrate forming a dichroic polarizer. This alignment process allows continuous production of large-area polarizing films at low cost compared with the current technology that requires stretching of the films. Thin coatings can be applied to flexible plastic films, glass, or rigid plastic substrates. Direct coating of the polarizing material on glass eliminates several process steps in liquid-crystal display production since lamination of the polarizing film is no longer required. These new polarizing films have a high optical performance including a polarizing efficiency of above 98% and a dichroic ratio as high as 7.7.
Synthesis and Characterization of Luminescent ZnO Powders Produced by Thermally-Induced Doping
Authors: Allieri B. , Depero L. E. , Sangaletti L. , Antonini L. , Bettinelli M. 
Published: April 2011

AbstractA low cost and efficient method of doping pure zinc oxide powders for luminescence applications is presented. The powders have been obtained from pure, non-luminescent ZnO by thermally induced doping under a nitrogen flux and in the presence of ZnS powders. Structural characterization has been carried out by X-ray diffraction analysis (XRD), while luminescence properties have been studied with both a spectrofluorimeter and microraman spectrometer. Emission spectra have shown an increase of the luminescence with treatment temperature. The XRD patterns of all samples showed, along with reflections of the hexagonal phase of ZnO, other reflections ascribed to the hexagonal phase of ZnS. Upon further annealing in air at 800°C, the ZnS reflections disappear even though the luminescence still persists with a comparable intensity. Luminescence is ascribed to ZnO reduction due to the interaction of S with ZnO. It has also been observed that excitation with a He-Ne laser beam (λ=633 nm) with a high specific power (5×10−3 W·µm−2) yielded blue-green luminescence in spite of excitation below the band-to-band absorption threshold.
Luminescence Properties of Thin-Film SrS:Cu Phosphors for Electroluminescent Displays
Authors: Jones T.C. , Park W. , Mohammed E. , Wagner B.K. , Summers C.J. , Sun S.S. 
Published: April 2011

AbstractThe origin of the electronic fine structure in thin-film SrS:Cu has been interpreted in terms of the several possible perturbations including spin-obit coupling, the Jahn-Teller effect and low symmetry splittings. Photoluminescence excitation measurements showed that the peak position of the excitation bands were independent of temperature suggesting that the electronic fine structure in our system was not due to the Jahn-Teller effect. Selective excitation measurements revealed that no peak shift occurs with changing excitation wavelength, indicating that Cu+ pairs or aggregates and Cu+-defect coupled centers were not existent in our system. Finally, several models were proposed for off-center displacements of Cu in SrS, since a rigorous treatment of these displacements is difficult. Both the tetragonal and trigonal distortion models for a <111> displacement yielded reasonable distortions parameters of 0. 16Å and 0.11Å, respectively. However, crystal field analysis showed that a <110> displacement was more likely since the energy level splitting scheme more closely resembled the observed data.
Al-RE-TM (RE = Rare-Earth Metals, TM = Transition Metals) Ternary Alloy Films for TFT-LCD Electrodes
Authors: Takayama Shinji 
Published: April 2011

AbstractThe effects of adding a third transition metal element, Co, Cu, Zr, or Ta, to Al-Nd (or Gd) alloy thin films were studied in order to investigate the changes in the film's microstructure and resistivity, and also their tendency to form hillocks or whiskers at high temperatures. The addition of Zr (or Ta), which has repulsive interactions with both Nd and Gd, to the Al-RE binary alloy films causes an increase of residual resistivity and enhances the formation of hillocks or whiskers at high temperatures. On the other hand, the addition of Cu or Co, which has attractive interactions with both Nd and Gd, results in a resistivity of less than 6 µωcm (depending on the content of added elements). Addition of either of these elements largely suppresses the growth of thermal defects after annealing at over 350 °C. The above results were explained by employing a theory of grain boundary segregation based on a chemical interaction between constituent elements of an alloy.