bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thin Films of SrFeO2.5+x - Effect of Preferred Orientation on Oxygen Uptake
Authors: Sanders Brian W. , Yao Jianhua , Post Michael L. 
Published: April 2011

ABSTRACTPulsed laser ablation has been used to deposit thin films of SrFeO25+x (x = 0 to ≈0.5). Previous work has shown that the orientation of the films, determined by powder x-ray diffraction depended strongly upon the deposition temperature. Films grown below 770 K showed little or no orientation. A growth temperature of 900 K resulted in films oriented (200). Growth temperatures of > 1000 K produced films oriented predominantly (110). At 673 K in an oxygen atmosphere, oriented films readily converted from the oxygen deficient brownmillerite form (x=0) to the oxygen rich cubic (or distorted cubic) perovskite form (x≈0.3). Films which exhibited no initial orientation did not react with oxygen under these conditions. Cycling non-oriented films between 230 and 800 ppm of oxygen in 101.3 kPa of nitrogen at 673 K resulted in weak (110) orientation. Once oriented, the films reacted readily with oxygen and exhibited measurable resistance changes. The conversion from oxygen deficient to oxygen rich form was monitored by x-ray diffraction and the DC resistance of the films.
Low Dielectric Constant, High Temperature Stable Copolymer Thin Films by Room Temperature Chemical Vapor Deposition
Authors: Gaynor Justin F. , Desu Seshu B. 
Published: April 2011

ABSTRACTPolyxylylene thin films grown by the chemical vapor deposition (CVD) process have long been utilized to achieve uniform, pinhole-free conformal coatings. They have recently been cited as possible low dielectric constant films for intermetal layers in high-speed ICs. Homopolymer films are highly crystalline and have a glass transition temperature around room temperature. We have demonstrated that room temperature copolymerization with previously untested comonomers can be achieved during the CVD process. Copolymerizing chloro-p-xylylene with perfluorooctyl methacrylate results in the dielectric constant at optical frequencies being lowered from 2.68 to 2.19. Copolymerizing p-xylylene with vinylbiphenyl resulted in films which increase the temperature at which oxidative scission occurs from 320 to 450C. Copolymerizing p-xylylene with 9-vinylanthracene resulted in a brittle, yellow film.
Asymptotic Behavior in Grain Growth
Authors: Wu David T. 
Published: April 2011

ABSTRACTHillert’s model of grain growth consists of a drift term in size space that leads asymptotically to a distribution function and a growth exponent not often observed. Later theories introduce a diffusion term that is either assumed to dominate the drift term or a correction to it. This paper shows that the lower order drift term alone determines asymptotic grain growth behavior. A possible conclusion is that experimental results may need to be reinterpreted.
Elastic Properties of FeNi/Cu and FeNi/Nb Metallic Superlattices Investigated by Brillouin Light Scattering
Authors: Carlotti G. , Socino G. , Xia Hua , Hu An , Jiang S. S. 
Published: April 2011

ABSTRACTThe Brillouin light scattering technique has been exploited in order to investigate the elastic properties of periodic superlattices consisting of alternating layers of Fe20Ni80 (permalloy) and either Cu or Nb. These multilayers, with total thicknesses ranging between 0.2 and 0.7 mm and with periods of typically 3-5 nm, present a polycrystalline structure with (110) texture for the Nb layers and (111) texture for both the FeNi and Cu layers. Measurement of the frequency position of the Brillouin peaks corresponding to the Rayleigh and Sezawa acoustic modes allowed the effective elastic constants of these structures to be determined. The values obtained are compared with those calculated from the elastic constants of the bulk materials, taking into account the polycrystalline nature of the superlattices and the crystallographic orientation of the layers.
Characterization of the Substrate Interface of Excimer Laser Crystallized Polycrystalline Silicon Thin Films
Authors: Anderson G. B. , Boyce J. B. , Fork D. K. , Johnson R. I. , Mei P. , Ready S. E. 
Published: April 2011

ABSTRACTExcimer laser crystallized Si thin films on fused silica substrates exhibit a peak in the average grain size as a function of laser energy density. The average grain size increases with increasing laser fluence until a maximum value , approximately 10 microns for a 100 nm thick Si film, is achieved. The peak in grain size is accompanied by a peak in the electron Hall mobility. Further increases in the laser fluence result in a decrease in the Si grain size and an increase in the intragranular defects. A small energy range of 40 mJ/cm2 exists in which this peak in grain size can be achieved. Cross section TEM has shown that when the peak laser fluence is exceeded, the fused silica substrate can be as rough as 17 nm. Atomic force microscopy. performed on the substrate surface after the Si has been etched off, also shows that the magnitude and spatial frequency of the roughness increases when the critical laser fluence is exceeded. This degradation of the interface may also produce sites for stacking faults to form during the solidification of the Si. This result and results of simulations of the temperature of the interface during crystallization suggests that the peak energy range exists after the complete melting of the Si thin film and before the silica substrate starts to soften.
Characterization of Sputtered Ge Film
Authors: Cho Jaeshin , Theodore N. David 
Published: April 2011

ABSTRACTThe electrical resistivity and microstructure of sputtered germanium film were characterized as a function of anneal temperature from 400 to 700°C. The as-deposited sputtered Ge film had an amorphous structure with resistivity of 165 Ω-cm which was maintained after annealing up to 540°C. After annealing above 550°C, the resistivity dropped by almost four orders of magnitude to ∼0.027 Ω-cm. The sharp transition of resistivity at 550°C is believed to be due to the recrystallization of Ge film from the as-deposited amorphous structure. The ohmic contact property on Ge films was also evaluated using sputtered tungsten. Low resistance ohmic contacts were obtained both on as-deposited and annealed Ge films, with typical ohmic contact resistance of 0.05 ± 0.008 Ω-mm on annealed Ge films. The W contacts were thermally stable after annealing up to 650°C.
Computational and Experimental Studies Of Grain Growth
Authors: Ngo Tue T. , Ahmadi Reza , Talin Alec A. , Williams R. Stanley 
Published: April 2011

ABSTRACTThis paper addresses the validity of the single particle growth law rn-r0n=Kt in describing the formation of 3D grains during the vapor deposition of thin metal films, especially with respect to the value of the exponent n. Computer simulations based on the Huygen’s construction showed that the grain size distribution at full surface coverage did not depend significantly on the specific model chosen for initiating growth from nuclei. The particle size distributions obtained experimentally by STM measurements of thin Au films deposited on glass substrates agreed very well with the simulation results for n=2.
Evolution Of Crystalline Microstructure in GeTe Thin Films for Optical Storage Applications
Authors: Libera M. 
Published: April 2011

ABSTRACTThe bit-erase process in phase-change optical storage is based on the amorphous to crystalline transformation. While there has been significant progress developing compositions and multilayered media for phase-change applications, quantitative studies of the crystallization kinetics and microstructural development are generally lacking. This paper describes work quantifying crystallization in GeTe thin films. Microstructural changes during isothermal annealing are measured usingin-situhot-stage optical microscopy. This technique measures the fraction crystallized, the number of crystallites, and crystallite radii as a function of time. These data are sufficient to deconvolute the individual contributions of nucleation and growth. We find an Avrami exponent of ∼4, consistent with time-resolved reflection/transmission studies. This exponent is due to 2-D growth at a constant rate plus transient nucleation. The data are used in a kinetic model to simulate non-isothermal crystallization during focused-laser heating characteristic of the bit-erase process.
Hydrogenation Mechanism of Top-Gated Polysilicon Thin Film Transistors
Authors: Ha Yong-Min , Han Jung-In , Han Chul-Hi , Kim Choong-Ki 
Published: April 2011

AbstractHydrogen diffusion paths in top-gated polysilicon thin-film transistors have been investigated by measuring the current-voltage characteristics of the transistors with various sizes after hydrogenation. Hydrogenation has been performed in ECR plasma sysytem. It is noted that hydrogen is introduced through three main paths instead of one predominant path. The hydrogen from different paths affects the device parameters differently.
Degradation Phenomena of low-temp. poly-Si TFT's Under Electrical Stress Before and After Hydrogenation
Authors: Kim Y. S. , Choi K. Y. , Jun M. C. , Han M. K. 
Published: April 2011

AbstractThe degradation mechanism in hydrogen passivated and as-fabricated poly-Si TFT's are investigated under the various electrical stress conditions. It is observed that the charge trapping in the gate dielectric is the dominant degradation mechanism in poly-Si TFT's which was stressed by the gate bias alone while the creation of defects in the poly-Si film is prevalent in gate and drain bias stressed devices. The degradation due to the gate bias stress is dramatically reduced with hydrogenation time while the degradation due to the gate and drain bias stress is increased a little. From the experimental results, it is considered that hydrogenation suppress the charge trapping at gate dielectrics as well as improve the characteristics of poly-Si TFT's.
A New Type TFT With Unique Operation And Simple Fabrication Process
Authors: Hattori Reiji , Tanida Yukinobu , Shirafuji Junji 
Published: April 2011

AbstractA thin film transistor (TFT) with a new structure and a unique operation principle has been pioposed. This TFT has Schottky barrier contacts at source and drain, and employs electron tunneling through the Schottky barrier. The first feature of this TFT is simplification of the production process because a self-aligned technique is applicable and an ion-implantation process is not necessary. These advantages are promising for low-cost production of active-matrix liquid crystal displays (AM-LCDs). In this letter, we propose of new type TFT and carry out 2-D device simulation on a simplified structure to show the fundamental characteristics of this transistor and to optimize impurity density, channel thickness, and barrier height.
Laser-Deposition Of High Luminance Thin Film Phosphors
Authors: Greer J. A. , Hook H. J. Van , Tabat M. D. , Nguyen H. Q. , Gammie G. , Koufopoulos P. F. 
Published: April 2011

AbstractHigh luminance (brightness) thin-film phosphor materials have potential use in a variety of applications including heads-up, helmet-mounted, and electroluminescent displays, as well as in emerging flat-panel displays based on field emitter technology. Phosphor materials in thin film form offer several advantages over conventional powder phosphor screens. Since the film is nearly fully dense and in intimate contact with the underlying substrate, thin film phosphors transfer heat to the face plate much quicker than conventional, more porous, powder phosphor materials. This allows thin film phosphor screens to be driven at higher power levels, and therefore produce higher luminance, assuming the efficiency of the powder and film are the same. Fully dense phosphor films have smaller surface area, and will outgas less than conventional powder phosphor materials. Thin film phosphors have smaller grain sizes than conventional powder phosphor materials which will provide for smaller spot size, and thus, higher resolution. Furthermore, in applications such as field-emitter displays, powder phosphor particles can be physically dislodged from the screen due to the high electric fields produced by the large potential difference between the anode screen and gate electrode (or cathode), or dislodged by arcing which may occur if a powder particle protrudes significantly above the screen surface. Dislodged particles or damage produced by arcing could degrade display performance. Dense, thin-film phosphor materials which are well adhered to transparent substrates will provide much smoother surface morphologies, and should be able to withstand significantly higher electric field strength without arcing or screen degradation due to the dislocation of particles.
Nanocrystalline Silicon Films for Large Area Displays: Preparation and Properties
Authors: Vepřek S. , Tamura H. , Rückschloss N. , Wirscheui Th. 
Published: April 2011

AbstractWe discuss the possible preparation techniques of the light emitting nanocrystalline silicon for large area electroluminescence (EL) displays and the control and optimization of the EL properties of the material. Some open problems are addressed and their possible solutions briefly discussed.
Considerations for Large Area Fabrication Of Integrated a-Si and Poly-Si TFTs
Authors: Mei P. , Anderson G. B. , Boyce J. B. , Fork D. K. , Hack M. , Johnson R. I. , Lujan R. A. , Ready S. E. 
Published: April 2011

AbstractThe combination of a-Si low leakage pixel TFTs with poly-Si TFTs in peripheral circuits provides an excellent method for reducing the number of external connections to large-area imaging arrays and displays. To integrate the fabrication of the peripheral poly-Si TFTs with the a-Si pixel TFTs, we have developed a threestep laser process which enables selective crystallization of PECVD a-Si:H. X-ray diffraction and transmission electron microscopy show that the polycrystalline grains formed with this three-step process are similar to those crystallized by a conventional one step laser crystallization of unhydrogenated amorphous silicon. The grain size increases with increasing laser energy density up to a peak value of a few microns. The grain size decreases with further increases in laser energy density. The transistor field effect mobility is correlated with the grain size, increasing gradually with laser energy density until reaching its maximum value. Thereafter, the transistors suffer from leakage through the gate insulators. A dual dielectric gate insulator has been developed for these bottom-gate thin film transistors to provide the correct threshold voltages for both a-Si and poly-Si TFTs.
The Low Temperature Polysilicon TFT Technology for Manufacturing of Active Matrix Liquid Crystal Displays
Authors: Morita Tatsuo , Tsuchimoto Shuhei , Hashizume Nobuo 
Published: April 2011

AbstractThe amorphous silicon thin transistor (a-Si TIFT) has successfully industrialized the active matrix liquid crystal displays (AMLCDs), which would get a vast market on the basis of their wide potential use for displays. Whereas, the polysilicon TFT (p-Si TFT) also has been intensely investigated and intended to realize smarter AMLCDs, with monolithic peripheral circuits.In this paper, we will discuss the applicable range of low temperature p-Si TFTs compared with high temperature p-Si TFTs. After reviewing the materials which comprise low temperature p-Si TFTs, we will introduce our self aligned aluminum gate process which could allow fast addressing even in enlarged AMLCDs in the future.
The Use of Injection Locked Magnetrons as a Source Microwave Processing Applications
Authors: Walker Chris M. 
Published: April 2011

ABSTRACTThe Injection Locked Magnetron (ILM) has been used as a source of coherent power in a number of radar systems. It has a number of characteristics that make it particularly suitable to heating applications, above competing tube types used in radar applications.Power available is dependent upon the frequency of operation, ranging from several hundred watts at Ku-band to tens of kilowatts at L-band. Operation could be either cw or pulsed, but at higher power levels pulsed operation would be required. Designs for tubes at 1 GHz and 15 GHz will be presented.ILMs could be made at any frequency from 800 MHz to 20 GHz, beyond which the magnetron becomes either too large to be practical or too small to fabricate. Locking bandwidths are typically 0.5%, sufficient to be able to guarantee the tube remains locked at the required operating frequency. A tuner would increase the tube life and compensate for frequency drift effects.The tube life is dependent on the desired frequency of operation, ranging from several hundred hours at high frequency to an order of magnitude higher at low frequency. Adding a tuner will increase this several fold. ILMs are inherently rugged and may be run in any orientation, having been developed for airborne radar applications. Tubes are operated directly into a circulator and consequently can operate into high VSWR.The magnetron is a low cost tube, hence its use in domestic microwave ovens. ELMs have a similar part count and complexity. Efficiency varies from approximately 45% in Ku-band to 80% at L-band. Operating voltages are lower for ILMs than other vacuum tubes, at 1 GHz a 100 kW system would require 20 kV and for a 15 GHz 200 watt system, a 2 kV power supply would be required. These would run in the region of 10% duty cycle, 1 kHz PRF. Tubes would have integral rare earth magnets and require cooling water. The required quantity of tubes would be the most significant cost driver.
Microwave Diagnosis of Carbon Black Rubber Compounds and Porosity Estimation in Composites
Authors: Zoughi Reza , Ganchev S. I. , Bhattacharyya J. , Gray S. , Radford D. 
Published: April 2011

ABSTRACTThe results of an in depth study of the dielectric properties of various rubber compounds at different microwave frequencies are discussed. Subsequently, the influence of carbon black volume percentage on the dielectric properties of rubber is studied in a wide frequency range (5 -24 GHz). The results show that the real and imaginary parts of rubber dielectric constant increase as a function of increasing carbon black percentage. Frequencies around 5 GHz show more sensitivity to small changes in the carbon volume content. The presence of curatives in uncured rubber samples is detected, which is an indication of the sensitivity of microwaves to the chemical reaction triggered by these curatives. Similar approach is used to measure the air content in specially prepared model material (plastic microbaloon-filled epoxy) samples with varying degrees of uniformly distributed air inclusion. The results of these measurements for a wide range of frequencies is also reported. Measurement analysis resulted in detecting variation in the air volume fraction of around 1.5%. The results confirm the utility of microwave NDE techniques for local porosity detection and evaluation in dielectric composites.
Microwave Based Civil Structure Inspection Device
Authors: Sohns C. W. , Bible D. W. 
Published: April 2011

ABSTRACTA microwave based “wall probe” has been developed which is capable of nondestructive evaluation of architectural structures. By using microwaves in the 8 to 12 GHz range this probing instrument can detect subsurface characteristics through concrete, brick, wood or other building materials to depths in excess of 12 inches.The instrument interrogates a structure from a single side by transmitting a microwave signal into the surface at some angle of incidence and receiving the reflected signal some distance away on the same side of the structure. The transmitted signal is partially reflected at each internal boundary of different dielectric constant, giving a composite reflection which contains information from each internal layer. The reflected composite signal is compared in phase and amplitude to the transmitted signal and that reading is considered the “signature” of the structure under test. Computer algorithms analyze the signature for recognizable features and nonstandard construction.
Decay Method for Measuring Complex Dielectric Constants During Microwave Processing
Authors: Iny O. , Barmatz M. 
Published: April 2011

ABSTRACTWe have developed a fast in-situ method for measuring the quality factor, Q, and resonant frequency, fr, for an isolated microwave resonant mode. The mode resonant frequency was continuously monitored using a phase modulation frequency tracking technique. The quality factor was determined by periodically switching off the microwave power and fitting the decay curve to an exponential. The cavity perturbation method was used with small spherical samples (ka « 1). Combining the Q and fr data with a non-contact measurement of the sample temperature permits the calculation of the temperature dependence of the real (ε′) and imaginary (ε″) dielectric constants. Because of the speed of this technique (≈1 μSce), it can be used during processing to continuously measure the dielectric constants of the material without perturbing the sample temperature. Measurements were performed using isolated TM010 and TEI11 cylindrical cavity modes. Care was taken to minimize the perturbing effects of the sample support. The accuracy of the frequency tracker was verified at room temperature from measurements on several alumina spherical samples. The decay technique was also verified from measurements on several small spherical nylon samples.
Mathematical Model of Thermal Spikes in Microwave Heating of Oxide Ceramic Fibers
Authors: Thomas J. R. , Unruh Wesley P. , Vogt Gerald J. 
Published: April 2011

ABSTRACTExperiments on microwave sintering of ceramic fibers in a single-mode cavity have revealed the presence of thermal spikes and “hot spots” which sometimes travel along the fiber and eventually disappear. They are triggered by relatively small increases in microwave power, and thus have obvious implications for the development of practical microwave-based fiber processing systems. These hot spots are conjectured to originate at slight irregularities in the tow morphology, and propagate as the result of solid phase transitions which take place at elevated temperatures and reduce the dielectric loss coefficient є”.An elementary mathematical model of the heat transfer process was developed which reproduces the essential features of the observed phenomena, thus lending support to our conjecture. This model is based on the assumption of one-dimensional heat conduction along the axis of the fiber tow, and radiation losses at the surface.
Microwave-Enhanced Regeneration of Adsorbents
Authors: Weissenberger Arne P. , Schmidt Philip S. 
Published: April 2011

AbstractAn experimental investigation was carried out to determine the regeneration characteristics of adsorbent beds using microwave heating. Tests were performed with water on F-200 activated alumina and on types 4A and 13X zeolite molecular sieves and with methanol on 4A and 13X zeolites. For these systems, microwave heating produced very high rates of regeneration with either gas purge or vacuum purge. Dielectric properties of both the adsorbent and the adsorbate affect the heating response. Temperature profiles in the adsorbent bed show that microwave heating eliminates the mass transfer front characteristic of conventional regeneration. This may have potential implications for improved bed life. The ultimate goal of the program is the recovery of volatile organic compounds (VOCs) by regenerating adsorbents with little or no dilution in a stripping medium.