bluuebunny/crossref_metadata_2025 huggingface dataset:
Uv Curable Liquid Crystals and Their Application
Authors: Takatsu H. , Hasebe H.
Published: April 2011

Some classes of liquid crystalline monoacrylates having no methylene spacers in a side chain have been prepared. The liquid crystalline monoacrylates have effects to reduce the driving voltage and the hysteresis for a light scattering display of Polymer Network liquid crystals prepared by photo-polymerization-induced phase separation.

By photo-polymerization of a chiral monoacrylate monomer in a nematic liquid crystalline host including a black dichroic dye, a polarizer free reflective Spiral Polymer Aligned Nematic (SPAN) Guest Host (GH) LCD exhibiting a low driving voltage has been fabricated. The effect of the spiral polymers made of some kinds of chiral monoacrylates for a Super Twisted Nematic (STN) LCD using SPAN liquid crystals is discussed.

UV-curable liquid crystals showing nematic phases at room temperature have been developed. By in situ photo-polymerization, the UV-curable liquid crystals can be utilized for the retardation film with high quality and good thermal stability. The fabrication of various kinds of retardation film using the UV-curable liquid crystals is discussed.

UV-curable liquid crystals having isotropic-nematic-smectic A phase sequence have been developed and the photo-polymerization at the state of their uniaxially oriented smectic A phases at room temperature is discussed. The polymerized film is optically uniaxial and transparent without light scattering.
Side Chain Liquid Crystalline Block Copolymers With Chiral Smectic C* Mesogens
Authors: Zheng Wen Yue , Hammond Paula T.
Published: April 2011

A new series of side chain liquid crystalline-amorphous diblock copolymers has been successfully synthesized using chiral mesogens. Anionic polymerization techniques have been used to make these monodisperse diblock materials. Preliminary studies suggest that these microphase segregated diblock copolymers exhibit a smectic C* phase. This mesophase exists between and above the glass transition temperatures of the two polymer blocks. Synthesis and characterization of these novel materials are discussed.
Silicon Parallel Multilayer Thin Film Solar Cells
Authors: Green Martin A. , Sproul Alistair B. , Puzzer Tom , Zheng Guang Fu , Basore Paul , Young Trevor
Published: April 2011

A new silicon parallel multilayer solar cell structure has recently been reported which can give high solar cell energy conversion efficiency from low quality silicon material. Advantages of this structure are described as is recent characterization work which compares the properties of grain boundaries in experimental devices to those predicted by earlier calculations.
Advanced, Thin, Polycrystalline Silicon-Film™ Solar Cells on Low-Cost Substrates
Authors: Hall Robert B. , Barnett Allen M. , Cotter Jeff E. , Ford David H. , Ingram Alan E. , Rand James A.
Published: April 2011

Thin, polycrystalline silicon solar cells have the potential for the realization of a 15%, lowcost photovoltaic product. As a photovoltaic material, polycrystalline material is abundant, benign, and electrically stable. The thin-film polycrystalline silicon solar cell design achieves high efficiency by incorporating techniques to enhance optical absorption, ensure electrical confinement, and minimize bulk recombination currents. AstroPower's approach to a thin-film polycrystalline silicon solar cell technology is based on the Silicon-Film™ process, a continuous sheet manufacturing process for the growth of thin films of polycrystalline silicon on low-cost substrates. A new barrier layer and substrate have been developed for advanced solar cell designs. External gettering with phosphorus has been employed to effect significant improvements leading to effective minority carrier diffusion lengths greater than 250 micrometers in the active silicon layer. Light trapping has been observed in 60-micrometer thick films of silicon grown on the new barrier-coated substrate. An efficiency of 12.2% in a 0.659 cm2 solar cell has been achieved with the advanced structure.
Determination of the Recombination Processes in Copper Ternary Chalcopyrites by Phototransport Measurements
Authors: Lubianmker Y. , Bitton G. , Balberg I. , Resto O. , Weisz S. Z.
Published: April 2011

We have measured the phototransport properties of CuGaSe2 films as a function of temperature. The simplest model which is consistent with all the experimental results consists of two recombination levels, one of which is donor-like and the other is acceptor-like. This model is similar to the symmetrical two-level model, which we have recently suggested for CuInS2 films. We thus conclude that this model, with slight variations, represents the general recombination level structure in all copper ternary chalcopyrites.
Chemical Bath Deposition of CdS Thin Films: Growth and Structural Studies
Authors: Zhu Yuming , Mao Dull , Williamson D. L. , Trefny J. U.
Published: April 2011

Chemical-bath-deposited CdS thin films from an ammonia-thiourea solution have been studied by x-ray diffraction, surface profilometry, ellipsometry, and other techniques. The compactness of the CdS films, structural properties of the films, and the growth mechanism have been investigated. For the deposition conditions used, we found that the film compactness reaches its maximum at a deposition time of 35 minutes. Films grown at longer deposition times are less compact, consistent with the CdS duplex layer structure proposed previously. This transition from compact layer growth to porous layer growth is important for depositing CdS films in solar cell applications. Based on x-ray diffraction (XRD) studies, we were able to determine the crystal phase, lattice constant, and other structural properties.
The Stability Improvement of a-Si:H Films for Photovoltaic Applications
Authors: Budaguan B. G. , Aivazov A. A. , Meytin M. N.
Published: April 2011

The origin of metastability in a-Si:H films deposited at different deposition conditions has been investigated by joint analysis of light-induced defect generation kinetics (Staebler-Wronski Effect) and differential scanning calorimetry (DSC) measurements. Light-induced defect generation kinetics were measured at elevated temperatures of 80–150 °C. DSC measurements were performed in a temperature range of 20 °C – 570°C. The films microstructure were studied by IR spectroscopy analysis.

The simulation of DSC curves has been used to deduce the kinetics of the low-temperature exothermic peak (LTEP) observed at 80–150°C. It was found that kinetic parameters of LTEP and SW effects has the same dependence on microstructure parameters, γ, which suggests their common nature. The analysis of a-Si:H stability improvement concerning the influence of films microstructure on the kinetics of relaxation processes is presented.
A Search for Degradation Mechanisms of CdTe/CdS Solar Cells
Authors: Meyers P. V. , Asher S. , Al-Jassim M. M
Published: April 2011

CdTe/CdS solar cells have demonstrated stability over thousands of hours of field testing, but have not yet established the same track record for reliability achieved by crystalline Si PV modules. In order to identify potential degradation mechanisms, this paper describes a series of experiments in which CdTe/CdS solar cells are subjected to combinations of temperature, voltage and illumination levels intended to stress the devices beyond levels which would be experienced in the field. During this process the devices display decreases in Voc and FF which are tentatively attributed to chemical changes at the low resistance contact to the CdTe and to changes in the electrical transport properties of the CdTe. Two thermally activated effects were observed depending upon stress bias. Reverse bias appears to degrade bulk CdTe electrical properties while forward bias strengthens a reverse diode which most likely is located at the back contact. Chemical analysis of the back contact region of the devices using XPS reveals strong oxide peaks in all stressed samples. Evidence of Cd diffusion into the Mo contacts is observed by SIMS and Auger. Mo diffusion into the CdTe is promoted by reverse bias stressing. Cu migration consistent with positively charged ions was indicated by SIMS.
Structural Characterization and Electrical Conductivity Percolation in (CdTe)1-x Tex
Authors: Morella G. , Katiyarb R. S. , Espinoza-Beltrán F. , Ramirez-Bon R. , Zelaya-Angel O.
Published: April 2011

Samples of the (CdTe)1-xTex diphasic system were grown by HWFE on glass plates kept at temperatures between 150 and 260 °C. The films have excess elemental tellurium varying between 12 and 67 vol%. X-ray analyses showed the samples to be diphasic with CdTe in the cubic phase and Te in the hexagonal phase. The excess tellurium concentration increased as the substrate temperature diminished. The critical volume fraction for conductivity percolation in the (CdTe)1-xTex system was determined to be around 0.4, which indicates a non-random distribution of the excess Te. Raman spectroscopy was used to characterize the Te phase across the conductivity percolation threshold. The integrated intensity of the first-order A1 mode increases dramatically at the percolation transition. Second-order Raman scattering from Te is also seen, but only for those samples with over 38 vol% Te. In addition, the A1 mode is shifted to higher energies in films with concentrations below the transition point, revealing that Te goes from a state of tensile stress into a relaxed state as the films pass from low to high conductivity. These results indicate that simultaneously with the Te network connectivity there occurs aggregation of the excess Te, which was initially located at the grain surfaces. This mechanism relieves the strain and gives rise to high conductivity and extended vibrational modes resembling those of bulk elemental tellurium at volume concentrations around 40% and above.
Jet Vapor Deposition of Transparent Conductive ZnO:Al Thin Films for Photovoltaic Applications
Authors: Han H. , Zhang J.-Z. , Halpern B. L. , Schmitt J. J. , Cueto J. Del
Published: April 2011

A novel, proprietary, and general approach to depositing thin films and coatings, The novel Jet Vapor Deposition TM (JVDTM) process is described, in which single or multiple “jets in low vacuum” are coupled with “mobile substrates” to generate a wide range of multicomponent, multilayer and “host-guest” thin films and coatings. Highly transparent and conducting aluminum-doped ZnO (ZnO:A1) thin films have been deposited at room temperature on glass slide, flexible polymer and thin film PV coated substrates by the JVDTM process. The thin films obtained from the optimized operating conditions have an average transmittance of about 85% in the visible range and electrical resistivities of 7 to 10×10-4 Ω-cm. Proper control of substrate bias, dopant content, deposition rate, and oxygen to metal ratio are the keys to depositing low resistivity and high transparency thin films.
Reversible Changes in the Electronic and Optical Properties of Micro-Crystalline ln2O 3-x: A Comparison with Amorphous In2O3-x
Authors: Pashmakov B. , Fritzsche H. , Claflin B.
Published: April 2011

The electrical conductance and optical absorption coefficient of microcrystalline indium oxide (c – In2 O 3-x ) can be changed reversibly by several orders of magnitude by photoreduction and reoxidation. Photoreduction is achieved by exposure to ultraviolet light hv ≥ 3.5eV in vacuum or an inert gas. The effects are similar to those previously observed in amorphous In2 O3-x
Spectrally Resolved Fill Factor Measurements on a-Si:H Based Solar Cell Structures
Authors: Wagner Michael , Peros Dimitrios , Guse Stephan , Böhm Markus
Published: April 2011

This work presents essential differences in the fill factors (FF) of pin and nip solar cell structures based on hydrogenated amorphous silicon (a-Si:H). The nomenclature “pin’ (‘nip’ respectively) determines the deposition sequence of the single layers. Fill factor measurements are carried out with illumination through p- and n-layers at different wavelengths. The use of laser light provides a wide range of illumination levels and photo current densities of up to 14mA/cm2. The spectrally resolved FF measurements indicate an incorporation of dopants in the i-layer depending on the layer deposited first. Nip and pin structures generally show opposite FF dispersion when illuminated through the same layer. However, due to the slight n-conductivity of intrinsic a-Si:H material, a weak boron incorporation leads to a net charge compensation in the ilayer. In contrast to other investigations we do not find a significant deviation in the open circuit voltages of the pin and nip devices as long as the deposition parameters of the single layers are identical.
a-Si/c-Si Solar Cells: Effect of Preparation and Processing Techniques on the Photovoltaic Properties
Authors: Jagannathan B. , Anderson W. A.
Published: April 2011

The photovoltaic (PV) properties of undoped amorphous silicon (a-Si)/ p-type crystalline silicon (c-Si) solar cells were found to improve by a hydrofluoric acid treatment of c-Si just prior to glow discharge deposition of a-Si. The short circuit current density (Jsc) improved from 2.7 to 23.5 mA/cm2 for an 0.1 μm thick a-Si layer. This also resulted in an improved spectral response of the solar cell in the violet region of the spectrum. The enhanced properties have been attributed to the improved carrier transport across the interface, as seen in the current-voltage-temperature relationships, and also PC-1D simulation of the devices. Solar cells of a similar type were also fabricated by dc magnetron sputtering of the a-Si layer. HF passivated cells (area ∼ 0.24 cm2) yielded about 9.5 % efficiency with Jsc of 30 mA/cm2 and a FF of 0.6, without use of an A/R coating. The variation of the PV properties of these cells was investigated as a function of a-Si thickness and c-Si doping.
Electromigration in VlSI Metallization Test Structures Stressed Over a Range Of DC Pulse Conditions and Frequencies up to 133 MHz
Authors: Malone D. W. , Hummel R. E.
Published: April 2011

Electrical resistance data were gathered from AI(Cu) VLSI metallization test structures during pulsed DC current stressing (15 mA peak) at elevated temperature (200 °C). Duty cycles of 50%, 67%, and 80% were applied at a frequency (repetition rate) of 133 MHz. Also, a duty cycle of 50% was applied at frequencies of 100 KHz, I MHz, and 133 MHz. The resistance-to-starting resistance ratio, R/Ro, was logged over time, and the data were used to extract the median time dependence of the resistance change. This, in effect, reveals the dependence of the median “failure” time on the R/Ro (or ΔR/Ro) criterion. An “enhancement factor” was defined as the ratio of the median “failure” time from a given pulsed test to that from a DC test with the same peak current. A weak dependence of this enhancement factor on R/Ro was found in the range examined. The degree of enhancement corresponds more closely to the average current density prediction than to the on-time prediction, although there is some small variation according to duty cycle and frequency.
Electromigration Damage Studied by 1/f Noise
Authors: Dagge K.
Published: April 2011

Thin polycrystalline aluminum films were investigated by high-resolution ac noisemeasurements before and after damaging by high direct current. Immediately after the interruption of the dc-stress a transient noise component was observed that was inversely proportional to the square of the frequency f (1/f2 -noise). It was caused by discrete jumps in the resistance presumably due to the relaxation of mechanical stress. The second component of noise was stable and in all cases approximately proportional to 1/f. The spectral density of 1/f-noise showed characteristic discrete steps as a function of damaging time, in contrast to the resistance which increased almost continuously up to the failure of the film. This indicates that nucleation-and-growth processes of mobile defects were observed in the noise measurements. Thus noise measurements might help to understand the microscopic process of electromigration.
1/f Noise in the Tunneling Current of thin Gate Oxides
Authors: Alers G. B. , Monroe D. , Krisch K. S. , Weir B. E. , Chang A. M.
Published: April 2011

We have observed fluctuations in the tunneling current through 3.5 nm gate oxides with a 1/f power spectrum where f is the frequency. For voltages in the direct tunneling regime we lind an anomalous current dependence of the noise relative to previous observations of noise in thin oxides. We present a simplified model for the current noise in terms of fluctuations in a trap assisted tunneling current that exists in the oxide in addition to the direct tunneling current. Current noise appears to be a very sensitive probe of trap assisted tunneling and degradation in oxides.
New Insights Into Oxide Trapped Holes And Other Defects: Implications For Reliability Studies
Authors: Oldham Timothy R. , Lelis Aivars J.
Published: April 2011

New insights into the nature of oxide trapped holes and other defects have been gained from ionizing radiation studies. Specifically, connections have been established between hole traps and neutral traps. The nature of the defects, how they are related to each other, and their implications for reliability studies will be discussed.
Effect of Nitrogen Diffusion in Ti and TiTiN Films for Future DRAM Bit Line Interconnects and Plugs
Authors: Drynan John M. , Koyama Kuniaki
Published: April 2011

The effects of nitrogen diffusion from both N2 gas phase and TiN solid phase sources on the characteristics of Ti/TiN bilayer and TiN/Ti/TiN trilayer films have been investigated in terms of both materials properties such as resistance, coloration, composition, and crystallinity, and prospective applications such as for DRAM bit line interconnections and contact-hole plugs. Using blank films it has been found, in coincidence with other work, that at the onset of N diffusion and hence low N concentrations within a Ti film, the sheet resistance increases and the Ti layer becomes a solid solution of N in hexagonal Ti. As the concentration increases, the sheet resistance reaches a maximum, after which it decreases abruptly and the structure becomes primarily tetragonal Ti2N phase. At higher concentrations the resistance stabilizes or increases slightly and the structure becomes more cubic TiN phase. Sheet resistances calculated from resistance measurements of Ti and TiN mono- and multilayer conductor lines with and without RTN and RTAr thermal treatments have shown that the conductor lines exhibit similar behavior to the blank films. In comparison with the mon-olayer lines, the multilayer ones are generally lower in resistance and more stable over a wider range of post-deposition process temperatures.
Post Metallization Damage Recovery Using Rapid Thermal Processing (RTP)
Authors: Thakur R. P. S. , Gonz´lez F. , DeBoer S.
Published: April 2011

Furnace annealing after plasma processing and other process steps such as implantation and contact formation in advanced CMOS processing are extensively used to improve the overall device characteristics. With an ever emerging trend towards lower thermal budget processing and the unique capabilities of RTP to provide that along with flexibility to change process ambients, we present the results of our experiments to do low temperature mixed gas and pure hydrogen anneals in RTP and study its effects on junction leakage and transistor characteristics.

Recently, with the advent of the contact plug technology, the sintering function is not as important as the alloy effect on the transistor and junction device parameters. Therefore, the requirements for the alloy are more related to threshold voltage, (Vt) uniformity and reduced junction leakage. The key is that the hydrogen atoms diffuse far into the silicon to reach the dangling bonds at the field edge and by the transistors. The hydrogen rapid thermal processor (HRTP) can accomplish the basic device annealing function as long as there is sufficient time for hydrogen diffusion and reaction time. The aluminum metallization limits the temperature to 500°C due to increased metal roughness and increased metal resistance. Also, the hotter temperatures compete in the reaction by breaking hydrogen bonds as well as satisfying the dangling silicon bonds. The best ambient gas was at 100% hydrogen flow at low pressure with HRTP times in excess of one minute.
Rapid Thermal Oxidation of Silicon in Mixtures of Oxygen and Nitrous Oxide
Authors: Grant John M. , Karim Zia
Published: April 2011

Oxidation in nitrous oxide by conventional hot wall furnace processing and by rapid thermnal oxidation (RTO) has been a subject of much interest in recent years. RTO is a fundamentally different process than furnace oxidation, however, and the full effects of this type of processing on the oxidation kinetics are not well understood. Oxidation of silicon by RTO at a variety of pressures, temperatures, and oxidation gas mixtures has been studied. Although at lower temperatures (<850°C) the atmospheric pressure oxidation rate in nitrous oxide is very close to that in oxygen, at higher temperatures the oxidation rate in nitrous oxide is much lower than that in oxygen. At lower pressures in a RTO process, the oxidation rate in nitrous oxide is higher than that in oxygen. The effect of the nitrogen incorporated in the oxide acting as a diffusion barrier has been proposed as the mechanism of temperature dependence for atmospheric pressure oxidation in nitrous oxide. This does not explain the effects seen at lower pressures, however. We propose that some of the intermediate species produced in the decomposition of nitrous oxide into molecular nitrogen, molecular oxygen, and nitric oxide play a role in the initial stages of oxidation by RTO in nitrous oxide.
The Role of Thermal Radiative Properties of Semiconductor Wafers in Rapid Thermal Processing
Authors: Timans P. J.
Published: April 2011

Rapid thermal processing (RTP) has become a key technology in the fabrication of advanced semiconductor devices. As RTP becomes the accepted technique for an increasingly wide range of processes in device fabrication, the understanding of the basic physics of radiation heat transfer in RTP systems is also being extended rapidly. This paper illustrates the use of optical models for prediction of the thermal radiative properties of semiconductor wafers. Such calculations can be used to address many of the key issues of interest in RTP, including questions concerning temperature measurement and process repeatability.
Selective Deposition of Silicon and Silicon-Germanium Alloys by Rapid Thermal Chemical Vapor Deposition
Authors: Grant John M. , Ang Ming , Allen Lynn R.
Published: April 2011

Selective deposition of SiGe alloys by rapid thermal deposition has been studied using a commercially available Rapid Thermal Chemical Vapor Deposition (RTCVD) cluster tool. The precursors used in this work were dichlorosilane and germane diluted in either hydrogen or argon. An initial characterization was performed to find the appropriate temperature and GeH4 flow ranges to deposit epitaxial layers with low surface roughness. For layers with higher germanium concentration lower deposition temperatures are required to minimize surface roughness. The effects of the dilutant gas on the deposition were examined. An H2 dilutant affects the deposition by consuming chlorine released by the SiCl2H2 and forming HCI. When Ar is used as the dilutant, more chlorine is available for other reactions that can result in etching of the silicon surface. Finally, the effects of pre-deposition treatment were determined. When compared to a wet HF dip, a gas/vapor phase HF/methanol native oxide removal treatment appears to increase the initiation time for the epitaxial deposition reaction. This is most likely due to increased fluorine termination of the surface. When a wet HF or HF/methanol native oxide removal is followed by a UV-Cl2 process, the deposition reaction initiation time is reduced. The UV-Cl2 process was also found to etch silicon through the native oxide.
Integrated Two-Stage Processing of Microcrystalline Silicon Thin Films on SiO2 and Glass
Authors: Wolfe D. , Wang F. , Lucovsky G.
Published: April 2011

A novel two-stage low temperature plasma assisted deposition process, which separates interface formation from bulk film growth, was investigated for deposition of in-situ phosphorous doped microcrystalline silicon (μc-Si) thin films on SiO2 and glass substrates. We find that the bulk layer microstructure, as characterized by reflection high energy electron diffraction and Raman scattering spectroscopy, is the same whether or not a buffer layer is used. However, we find significant differences in the room temperature dark conductivity, and the dark conductivity activation energies.
Spanish Activities (Research and Industrial Applications) in the Field of Microwave Material Treatment
Authors: Civera José Manuel Catalá , Davó Elías De los Reyes
Published: April 2011

The GCM (Microwave Heating Group) within the Communications Department at the Technical University of Valencia is dedicated to the study of microwaves and their use in the current industrial processes in the Valencian Community and in Spain. To this end, a microwave heating laboratory has been developed and the benefits of incorporating microwave technologies into current industrial processes have been demonstrated. In this paper some of the industrial applications which are being investigated are presented.
Microwave Heating of Ceramic Laminates
Authors: Pelesko J. A. , Kriegsmann G. A.
Published: April 2011

The microwave heating of a ceramic laminate composed of three layers is modeled arid analyzed. Two materials with widely disparate effective electrical conductivity's comprise the laminate. The ratio of the these conductivities is exploited as a small parameter in the development of an asymptotic theory. Two physically distinct situations are considered. In the first, a low-loss ceramic is surrounded by lossy material. In the second situation, a lossy material is surrounded by a low-loss material. The results are physically interpreted to attain insight into the dynamics and parameter dependence of the microwave heating of ceramic laminates.
Investigations of Microwave Absorption in Insulating Dielectric Ionic Crystals Including the Role of Point Defects and Dislocations
Authors: Klein Benjamin D.B. , Meng Binshen , Freeman Samuel A. , Booske John H. , Cooper Reid F.
Published: April 2011

A theoretical model of microwave absorption in linear dielectric (non-ferroelectric) ionic crystals that takes into account the presence of point defects was synthesized and verified using NaCl single crystals. In the next stage of this research, we will introduce a controlled density of dislocations into the single crystal NaCl samples and study the effect on the microwave absorption mechanisms (ionic conduction, dielectric relaxation and multi-phonon processes) both theoretically and experimentally. Qualitative outlines of this modified theory are presented. The loss factor ε’ has been measured in the dislocation-free case by a cavity resonator insertion technique and the experimental results are in good agreement with the theoretical model. We describe the sample preparation technique that will be used to produce a controlled dislocation density in single crystal samples that will also be studied in our cavity resonator insertion system.
Microwave Effects on Spinodal Decomposition
Authors: Willert-Porada M.
Published: April 2011

Microstructural differences between microwave and conventionally annealed solid solution TiO2-SnO2 and TiO2-SnO2-(Al2O3)0,02-samples demixed by spinodal decomposition are reported. The decomposition is retarded upon microwave annealing as compared to conventional heat treatment. This result is in accordance with theoretical predictions, if a superposition of the microwave field with an internal periodic electrostatic potential resulting from kinetic effects is assumed.
Window Encapsulation in Car Industry by Using the 50 Ω RF Technology
Authors: Bernard J. P. , Barboteau Mr. , Collet L.
Published: April 2011

Throughout the world car industry has been using window encapsulation for a few years now. This technology is mainly used in production lines and is called RIM for polyurethane reaction injection moulding.

This technology, however brings about some problems such as:

– glass breaking during mould closure,

– high production cost,

– systematic rough edges.

The PSA Group (Peugeot-Citroën), a pioneer in this field, in collaboration with SAIREM has launched a new innovating process for window encapsulation by using the 50 Ω RF technology for gelling PVC Plastisol.

The study was followed by an industrial prototype. Industrial equipment was then installed at WEBASTO HEULIEZ for window encapsulation of the sunshine roof for the Citroën Xantia.

The authors describe the principle of window encapsulation and the different existing processes. He describes the 50 ΩRF technology, an industrial installation and the constraints of this technology in order to get maximum efficiency.

In the conclusion they present a technical and economical analysis of the different solutions for window encapsulation. They also present the advantages of the 50 Ω RF technology and the new opportunities it offers.

In the conclusion they present a technical and economical analysis of the different solutions for window encapsulation. They also present the advantages of the 50 Ω RF technology and the new opportunities it offers.
Microwave Sintering of Tungsten Carbide Cobalt Hardmetals
Authors: Gerdes T. , Willert-Porada M. , Rödiger K.
Published: April 2011

The variety of possible microstructures obtained upon microwave sintering of hardmetals is described with regard to microwave specific heating mechanisms. While the reduction of processing time and temperature is evident, the influence of the microwave sintering process on the microstructure is not fully understood. From microwave sintering experiments at different power levels processes that depends on the local field strength are identified. The mechanical properties of microwave sintered tool bits are compared with commercial WC-Co hardmetals. An incising wear resistance of MW-sintered hardmetals for speed turning of cast iron is found.
Statistical Comparative Analyses of Engineering Properties of Microwave and Conventionally Sintered Alumina
Authors: Binger K. R. , Freeman S. A. , Grellinger D. J. , Cooper R. F. , Booske J. H.
Published: April 2011

Processing conditions such as temperature, soak time, and heating rate affect the final density of conventionally-sintered and microwave-sintered ceramics. Of additional importance is the question of whether microwave-sintered ceramics display intrinsically superior macroscopic engineering properties compared with conventionally-sintered control specimens. An analysis using the Yates algorithm indicates that the processing condition which has the largest impact on the density of the specimen is the heating method (microwave vs. conventional). The microwave-sintered specimens resulted in higher densities and higher fracture strengths. However, it was determined that the higher fracture strengths were due to the higher sintered densities rather than a significantly different microstructure.
Temperature Distribution in a Flowing Fluid Heated in a Microwave Resonant Cavity
Authors: Thomas J. R. , Nelson Eric M. , Kares Robert J. , Stringfield Ray M.
Published: April 2011

This paper presents results of an analytical study of microwave heating of a fluid flowing through a tube situated along the axis of a cylindrical microwave applicator. The interaction of the microwave field pattern and the fluid velocity profiles is illustrated for both laminar and turbulent flow. Resulting temperature profiles are compared with those generated by conventional heating through a surface heat flux. It is found that microwave heating offers several advantages over conventional heating.
An Electronic Stopping Power Model in Single-Crystal Silicon From a Few KeV to Several MeV
Authors: Morris S. J. , Obradovic B. , Yang S. -H. , Tasch A. F. , Rubin L.
Published: April 2011

An electronic stopping power model for boron, arsenic, and phosphorus ion implantation into single-crystal Si is reported over the energy range fr'om a few keV to several MeV, for both offand on-axis implant angles relative to the <100> crystallographic direction. Combined with previously developed models for damage accumulation, this model allows physically-based simulation of 3-D profiles over an extremely wide range of implant conditions. In particular, this allows modeling of MeV implants which are being used more and more frequently.
Transient Enhanced Diffusion of Dopants in Preamorphised Si Layers
Authors: Claverie A. , Bonafos C. , Omri M. , De Mauduit B. , Assayag G. Ben , Martinez A. , Alquier D. , Mathiot D.
Published: April 2011

Transient Enhanced Diffusion (TED) of dopants in Si is the consequence of the evolution, upon annealing, of a large supersaturation of Si self-interstitial atoms left after ion bombardment. In the case of amorphizing implants, this supersaturation is located just beneath the c/a interface and evolves through the nucleation and growth of End-Of-Range (EOR) defects.

For this reason, we discuss here the relation between TED and EOR defects. Modelling of the behavior of these defects upon annealing allows one to understand why and how they affect dopant diffusion. This is possible through the development of the Ostwald ripening theory applied to extrinsic dislocation loops. This theory is shown to be readily able to quantitatively describe the evolution of the defect population (density, size) upon annealing and gives access to the variations of the mean supersaturation of Si self-interstitial atoms between the loops and responsible for TED. This initial supersaturation is, before annealing, at least 5 decades larger than the equilibrium value and exponentially decays with time upon annealing with activation energies that are the same than the ones observed for TED. It is shown that this time decay is precisely at the origin of the transient enhancement of boron diffusivity through the interstitial component of boron diffusion. Side experiments shed light on the effect of the proximity of a free surface on the thermal behavior of EOR defects and allow us to quantitatively describe the space and time evolutions of boron diffusivity upon annealing of preamorphised Si layers.
Conductive Tungsten-Based Layers Synthesized by Ion Implantation Into 6H-Silicon Carbide
Authors: Weishart H. , schöneich J. , Voelskow M. , Skorupa W.
Published: April 2011

We studied high dose implantation of tungsten into 6H-silicon carbide in order to synthesize an electrically conductive layer. Implantation was performed at 200 keV with a dose of 1.2×1017 W+cm−2 at temperatures between 200°C and 400°C. The influence of implantation temperature on the distribution of W in SiC was investigated and compared to results obtained earlier from room temperature (RT) and 500°C implants. Rutherford backscattering spectrometry (RBS) was employed to study the structure and composition of the implanted layers. Implantation at temperatures between RT and 300°C did not influence the depth distribution of C, Si and W. The W depth profile shows a conventional Gaussian shape. Implanting at higher temperatures led to a more confined W rich layer in the SiC. This confinement is explained by Ostwald ripening which is enabled during implantation at temperatures above 300°C. The depth of the implantation induced damage decreases slightly with increasing implantation temperature, except for 400°C implantation. The amount of damage, however, is significantly reduced only for implantation at 500°C.
Electron Beam Enhanced Precipitation in Highly Carbon Doped GaAs Layers
Authors: Werner P. , Gösele U. , Kohda H.
Published: April 2011

Highly carbon doped GaAs layers grown by metal organic vapor phase epitaxy (MOVPE) Has been investigated by transmission electron microscopy (TEM). Electron irradiation has been applied to generate point defects interacting with native defects, e.g., substitutional carbon. This irradiation induces periodically arranged striations perpendicular to the growth direction, which were observed in situ by TEM. Furthermore, precipitates (Ø= 10–15nm) were formed containing non-crystalline material, which most likely is gallium. To explain these phenomena a precipitation mechanism is proposed. It involvs small fluctuations of the incorporated C as well as the interaction of irradiation induced point defects, mainly As and C interstitials and As vacancies.
Ion Beam Modification of Cluster-Covered Silicon Surfaces
Authors: Gulko O. V. , Zinke-Allmang M. T.
Published: April 2011

Clusters of independently tailored areal density and size distribution were grown on semiconductor surfaces in ultra-high vacuum and used as masks for selective ion beam modification. First studies were undertaken to characterize the vertical interface between areas exposed to low energy ion beams and areas covered by clusters (crystalline silicon). Selective etching was employed to create a patterned surface as a substrate for heteroepitaxial growth of thick Ge layers to test defect density reduction due to finite size growth areas. The quality of the overlayers is discussed.
Monte Carlo Simulation of Cluster Growth and Defect Annealing
Authors: Fedorov A. V. , Veen A. Van , Hosson J. Th De
Published: April 2011

A computer program MODEX has been developed to predict the evolution of the irradiation defects in materials during ion implantation and subsequent annealing. The evolution of the defect clusters is simulated through a number of trapping and dissociation events. Two examples of the program application are presented: (1) 1 keV helium ion implantation in molybdenum up to doses of 1013 cm-2 with the subsequent ramp annealing up to 1400 K; and (2) 2.5 keV helium ion implantation in silicon with 1016 cm-2 with ramp annealing up to 1600 K. The simulation results are compared to the experimental results obtained by gas desorption techniques. The threshold dose needed for micro-cavity formation in silicon is discussed.
Computer Simulation of Displacement Cascades in α-Zirconium
Authors: Gao F. , Wooding S. J. , Bacon D. J. , Calder A. F. , Howe L. M.
Published: April 2011

The damage produced in α-zirconium at 100 K by displacement cascades with energy up to 20 keV has been investigated by MD simulations. In agreement with modelling of fcc and bcc metals, the defect production efficiency in zirconium is well below the NRT estimate. The number and size of clusters, both vacancy and interstitial, are increased by increasing PKA energy, and clusters containing up to 25 interstitials and 30 vacancies were formed by 20 keV cascades. Most interstitial clusters have dislocation character with perfect Burgers vectors of the form 1/3<1120>, but a few metastable clusters are formed and are persistent over the timescale of MD simulations. Collapse of the 30-vacancy cluster to a faulted loop on the prism plane was found to occur over a period of more than 100 ps
The Dependence of Proton Irradiated Microstructure on Dose, Temperature and Composition of Austenitic Stainless Steels
Authors: Gan J. , Allen T. , Was G. S.
Published: April 2011

The radiation-induced microstructure of austenitic stainless steel was investigated using proton irradiation. Samples of Fe-20Cr-24Ni and Ni-18Cr-9Fe were irradiated using 3.2 MeV protons at a dose rate of 7×10−6 dpa/s between 300°C and 600°C. The irradiation produced a microstructure consisting of dislocation loops and voids in both alloys. The number density and size of dislocation loops and voids are strong functions of irradiation temperature with the number density decreasing and the size increasing with temperature for both defects. The dose dependence of dislocation loop density saturated around 1.0 dpa for Fe-20Cr-24Ni and 0.3 dpa for Ni-18Cr-9Fe. The microstructure evolution in the nickel base alloy is faster than that in Fe-20Cr-24Ni. The dose and temperature dependence of proton irradiated Fe-20Cr-24Ni closely follow that of neutron irradiated austenitic stainless steels. The changes in yield strength due to irradiation were estimated from nano indenter hardness measurements and compared to calculation using a dispersed barrier hardening model. Results were in close agreement with each other. Yield strength changes as a function of dose for proton irradiated Fe-20Cr-24Ni are similar to those resulting from neutron irradiation of austenitic stainless steels.
Modeling of Radiation-Induced Segregation in Austenitic Fe-Cr-Ni Alloys
Authors: Allen T. R. , Was G. S.
Published: April 2011

To improve the ability to predict radiation-induced segregation (RIS) in austenitic Fe-Cr-Ni alloys, a model for predicting RIS is developed which calculates diffusion parameters based on local atomic configuration. Comparisons of RIS measurements in austenitic iron-base and nickelbase Fe-Cr-Ni alloys with calculations using the Perks vacancy-driven RIS model have shown that to accurately predict segregation trends, composition specific diffusion parameters must be used. This requirement limits the ability of the Perks model to predict segregation in Fe-Cr-Ni alloys for which no prior segregation measurements exist. To overcome this limitation, the improved model calculates migration energies using pair interaction energies to account for composition dependent diffusivities. The advantages of this approach are that a single set of input parameters can be used to describe a wide range of bulk alloy compositions, and the effects of local order can be easily incorporated into the calculations. A description of the model is presented, and model calculations are compared to segregation data to show that significant trends in the measured segregation data can be modeled using a single set of input parameters.
Irradiation Spectrum and Ionization-Induced Diffusion Effects in Ceramics
Authors: Zinkle S. J.
Published: April 2011

There are two main components to the irradiation spectrum which need to be considered inradiation effects studies on nonmetals, namely the primary knock-on atom energy spectrum and ionizing radiation. The published low-temperature studies on A12O3 and MgO suggest that the defect production is nearly independent of the average primary knock-on atom energy, in sharp contrast to the situation for metals. On the other hand, ionizing radiation has been shown to exert a pronounced influence on the microstructural evolution of both semiconductors and insulators under certain conditions. Recent work on the microstructure of ion-irradiated ceramics is summarized, which provides evidence for significant ionization-induced diffusion. Polycrystalline samples of MgO, A12O3, and MgAl2O4 were irradiated with various ions ranging from 1 MeV H+ to 4 MeV Zr+ ions at temperatures between 25 and 650°C. Cross-section transmission electron microscopy was used to investigate the depth-dependent microstructure of the irradiated specimens. Dislocation loop nucleation was effectively suppressed in specimens irradiated with light ions, whereas the growth rate of dislocation loops was enhanced. The sensitivity to irradiation spectrum is attributed to ionization-induced diffusion. The interstitial migration energies in MgAl2O4 and A12O3 are estimated to be ≤0.4 eV and ≤0.8 eV, respectively for irradiation conditions where ionization-induced diffusion effects are expected to be negligible.
Growth Transients During the Nucleation of GaInAs on InP by Organometallic Vapor Phase Epitaxy
Authors: Emerson D.T. , Shealy J.R.
Published: April 2011

By using lattice matched short period (50 Å) GaInAs/InP superlattices, we are able to extensively characterize, ex-situ, nucleation of thin (20–30 Å) GaInAs layers on InP. Systematic variation of the interface formation technique allows us to understand how parameters such as growth temperature and growth rate can contribute to interfacial roughness, giving rise to growth transients near the interfaces that are unexpected from characterization of thick layers. Growth of multi-period structures such as those studied here enables the use of Raman scattering, photoluminescence, and double crystal x-ray diffraction to determine that Ga incorporation is favored over In incorporation near the InP to GaInAs interfaces. Furthermore, by examining the surfaces and structural properties of epitaxial layers (15 Å-1 μm) of both InP and GaInAs with atomic force microscopy and Raman scattering, respectively, we are able to correlate results on the superlattice structures with results from single layers. Finally, we show how understanding the nucleation of thin films through the process described here enables the growth of complicated, previously unrealizable, heterostructures for use in novel optoelectronic devices.
Mound Formation and Coarsening in Homoepitaxial Growth
Authors: Amar Jacques G. , Family Fereydoon
Published: April 2011

The effects of instabilities which lead to mound formation and coarsening in homoepitaxial growth on metal (100) surfaces are discussed. These include an instability due to the Ehrlich-Schwoebel step barrier to interlayer diffusion as well as an instability due to step-adatom attraction at ascending steps. A unified picture of the effects of attractive and repulsive interactions at ascending and descending steps on surface morphology and island nucleation is presented. An analytic calculation of the selected mound angle and critical temperature for mound formation as a function of both the Ehrlich-Schwoebel step barrier and the barrier to diffusion towards an ascending step is also presented. Depending on the sign of the step barrier and the magnitude of the prefactor for diffusion over a step various scenarios are possible, including the existence of a critical temperature for mound formation above which (for a positive step barrier) or below which (for a negative step barrier) quasi-layer-by-layer growth will be observed. A theoretical analysis also leads to an accurate prediction of the observed mound angle for Fe/Fe(100) deposition at room temperature. The general dependence of the mound angle, surface skewness, and mound coarsening exponent on temperature, deposition rate, and strength of the step barrier is also studied via kinetic Monte Carlo simulations of bcc(100) growth and compared with recent experiments.
The Role of Roughness in Texture Development
Authors: Whitacre J. F. , Bilello J. C. , Yalisove S. M.
Published: April 2011

To examine the dependence of in-plane texture development on substrate surface morphology, deposition was performed on an intentionally roughened surface. 2 μm thick sputter deposited Mo films were macroscopically roughened by ion bombardment. This process created aligned mounds on the surface which were ˜1 μm in length, ˜0.1 μm in width and ˜0.04 miimn height. To remove crystallographic orientation effects, this surface was coated with a thin layer of graphite. Using these roughened, coated surfaces as a new substrates, the role of well defined macroscopic roughness in subsequent thin film growth was probed. Mo films were deposited onto these prepared substrates which were placed on a rotating platen under a stationary ion sputter source. When the mounds are aligned with their elongated axes normal to the rotation direction, little to no in-plane texture is found. The same deposition on a flat surface, or on the roughened surface with the mounds oriented parallel to the platen rotation direction, gives films with a high degree of in-plane texture. Scanning electron microscopy, transmission electron microscopy, and transmission electron diffraction data will be presented to corroborate these findings.