bluuebunny/crossref_metadata_2025 huggingface dataset:
AlGaAs Surface Reconstruction after Cl2 Chemical Etch and Ultra High Vacuum Anneal
Authors: Hong M. , Mannaerts J. P. , Grober L. H. , Thiel F. A. , Freund R. S.
Published: April 2011

We report attaining (3x2) surface reconstruction with streaky reflection high energy electron diffraction (RHEED) patterns on Al0.4Ga0.6As after in-situ Cl2 chemical etch and ultra high vacuum (UHV) anneal. Secondary ion-mass spectrometry (SIMS) analysis at the regrown/etched Al0.4Ga0.6 As interface reveals impurities of O and C in the level of (5±1) × 1012 cm-2 and (3±1) × 1012 cm-2, respectively. These impurity levels are 10 times less than those of Al0.4Ga0.6 As after in-situ electron cyclotron resonance (ECR) plasma etch and UHV anneal without Cl2 chemical etch.
Doping Efficiency and Deep Traps in MOCVD-Grown InGaAlP as Influenced by Stoichiometry and Hydrogen Passivation
Authors: Gorbylev V.A. , Chelniy A.A. , Chekalin A.A. , Polyakov A.Y. , Peaon S.J. , Smirnov N.B. , Govorkov A.V. , Leiferov B.M. , Popova E.V. , Kusikov V.A. , Balmashnov A.A.
Published: April 2011

It is shown that the low electrical activity of Zn in MOCVDgrown InGaAlP is related to hydrogen passivation during growth and that the effect is sensitive to growth conditions. We also discuss the results of hydrogen plasma treatment of p- and n-InGaAlP layers.
Ge Optical Interconnects on a GaAs Surface
Authors: Dubey M. , McLane G.F. , Jones K.A. , Lareau R.T. , Eckart D.W. , Han W.Y. , Roberts C. , Dunkel J. , West L.C.
Published: April 2011

Germanium films were deposited on GaAs (100) substrates at temperatures between room temperature (RT) and 500°C using ultra high vacuum (UHV) E-beam and sputtering deposition methods. The Ge film deposited in UHV at 100°C was amorphous and had a flat absorbance curve over the range investigated, 4000 - 500 cm-1, with a value of 0.03 at 1000 cm1 (10μm). Films deposited by E-beam at RT and 50°C had comparably low absorbances, but they contained a peak at 830 cm-1, which was possibly due to absorption by a Ge-O bond. The amorphous film deposited at 150°C and the single crystal films deposited at 400 and 500°C by E-beam had larger absorbances caused by free carrier absorption. The amorphous Ge sputtered film deposited at RT had a relatively low absorbance, but it contained the absorption peak attributed to Ge-O. The absorbance increased dramatically when it was annealed at 400 or 500°C due to the rapid out diffusion of Ga and As through the relatively open structure.
Plasma assisted nitrogen doping of ZnSe grown by MOVPE
Authors: Cloitre T. , Briot O. , Briot N. , Gil B. , Aulombard R.L.
Published: April 2011

We designed a plasma cell for nitrogen doping of ZnSe, using a metal organic vapour phase epitaxy (MOVPE) horizontal reactor. With the following growth conditions: Tg=300°C, P=1 Torr and a molar VI/II ratio of 5, successful p-type doping was obtained, as assessed by photoluminescence experiments, but with a free carrier concentration still too low to be detected by transport measurements. The passivation of nitrogen active species by hydrogen is discussed. The possible interaction with the carrier gas has been studied through the use of H2, N2 and He as carrier gases. We demonstrate that the use of helium as carrier gas leads to sensible improvement of the photoluminescence features related to nitrogen acceptor. On the other hand, the use of N2 as carrier gas leads to poor homogeneity of the layers with few effects on the doping level.
Effects of Post-Deposition Processing on the Ultimate Grain Size in Metastable Semiconductor Thin Films to be Used in IR Detectors
Authors: Lee Susanne M
Published: April 2011

Through post-deposition annealing in a differential scanning calorimeter (DSC), we have manufactured both thin (200 nm) and bulk (8000 nm) single phase films of crystalline Ge1–xSnx, using rf sputtering. The Sn concentrations produced ranged up to 31 at.%, well beyond the solid solubility limit of this system. There was a marked difference, in the asdeposited structure, between thick and thin films produced under the same deposition conditions. Quantitative models for both systems are given in this paper and were deduced frorn DSC measurements in conjunction with electron microscopy. The metastable crystalline state in the thin films formed by nucleation and growth from an amorphous phase; whereas in the thick films, the desired phase was already present in the as-deposited films and only growth of preexisting grains was observed upon post-deposition annealing. When annealed to high temperature, the Sn phase separates from the alloys and we postulate here that it does so by nucleation and growth of β-Sn. With this hypothesis, the Sn separation in the 8000 nm thick films was accurately modeled by a two-mechanism process, however, in the 200 nm thick films, only one phase separation mechanism was necessary to accurately fit the data. Both models were corroborated by the subsequent melting behavior of the phase separated Sn which, though it varied depending on the sample being measured, always exhibited a melting endotherm starting 25–35°C lower than the bulk melting temperature of Sn. Speculation on the reasons for this are presented.
Phase Formation and Microstructural Development During Solid-State Reactions in Ti-Al Multilayer Films
Authors: Michaelsen Carsten , Wöhlert Stefan , Bormann RÜdiger
Published: April 2011

The phase selection which is generally observed in the early stages of solid-state reactions was studied using Ti-Al multilayer films as a model system.

Although all Ti-Al intermetallic phases have similar driving forces of about 30 kJ/g-atom, TiAl3 is the only phase which is formed as long as the reactants are not consumed. The critical thickness beyond which a second phase is formed is larger than 100 μm. We found that the formation of TiAl3 takes place by nucleation and growth, demonstrating that the driving force available for first-phase formation is considerably reduced by a preceding formation of solid solutions. Furthermore, we observed that nucleation continues at later stages, indicating that non-equilibrium conditions are maintained which are possibly influenced by grain-boundary diffusion. However, the phase selection is determined by the different growth velocities, being much higher for TiAl3 than for all other phases.
Artificially Synthesized Non-Coherent Interfaces in Fe-Ti Multilayers and their Influence on Solid State Reactions
Authors: Yan Z.H. , Trudeau M.L. , Van Neste A. , Schulz R. , Ryan D.H. , Tessier P. , Bormann R. , Ström-Olsen J.O.
Published: April 2011

The influence of the interfacial structure on the solid state reaction products in Fe-Ti multilayers has been studied using various preparation conditions and characterization techniques. Sharp and diffused interfaces were produced by using either sequential or co-evaporation in the interfacial region. The reaction product, in the case of the sharp interface, is the bcc supersaturated solid solution of Ti(Fe) while, in the case of the diffused interface, an amorphous phase is formed. Therefore, nucleating the amorphous phase at the interface by local co-evaporation alters the reaction path observed in Fe-Ti multilayers. The solid state reactions were studied using low and high angle X-ray diffraction and Mossbauer measurements. The results are discussed in light of recent thermodynamic calculations on the Fe-Ti system.
Correlation of Structure and Properties in Thin-Film Magnetic Media
Authors: Nolan T. P. , Sinclair R. , Ranjan R. , Yamashita T. , Tarnopolsky G. , Bennett W.
Published: April 2011

Correlation of detailed microstructural information obtained from a temperature series (25–275°C) of otherwise identical CoCrTa/Cr recording media with detailed recording performance measurements demonstrates two mechanisms for magnetic isolation.

Media were prepared by sputter deposition of 75 nm Cr underlayers and 60 nm Co84Cr12Ta4 layers onto circumferentially textured NiP plated aluminum substrates using an Intevac MDP-250 machine.

High-resolution transmission electron microscopy (HRTEM) and high-resolution scanning electron microscopy (HRSEM) show columnar isolation by voiding, via the mechanism of shadowing during low temperature growth. Shadowing decreases with increasing temperature until voiding disappears at 150°C. At high temperature (275°C), large intergranular separation is observed, which has been attributed to elemental segregation. This separation decreases as temperature decreases, until it disappears at 150°C.

Detailed magnetic recording measurements show that the maximum normalized media noise power is observed at 150°C. It decreases as more isolated structures are formed by increasing or decreasing temperature. Uniform magnetization noise, a measurement related to crosstrack correlation length within a magnetization transition also shows this trend.

It is suggested that HRTEM shows two different microstructural features that control magnetic correlation lengths and resulting media noise.
Atomically Layered Structures for Perpendicular Magnetic Information Storage
Authors: Lairson Bruce M. , Visokay M. R. , Sinclair R. , Brennan S. M. , Clemens B. M. , Perez J. , Baldwin C.
Published: April 2011

Layered structures can possess a high volumetric density of interfaces, which can result in novel magnetic properties. We report magnetic characteristics of two types of atomically layered structures, (001) oriented intermetallics with the CuAu(I) crystal structure and (111) oriented artificial multilayers. C-axis oriented superlattices of PtFe, PtCo, PdFe and PdCo with the layered CuAu(I) structure, possess large magnetic anisotropies and novel magneto-optic properties relative to the corresponding random alloys. These films are produced by annealing, with tetragonality and magnetic anisotropy developing in a fashion which depends on the initial bilayer period and annealing parameters. (111) oriented artificially grown Pd/CoCr multilayers are reported for perpendicular magnetic recording applications. Using a perpendicular contact probe transducer, the multilayers exhibit two times the readback signal of CoCr media. The multilayers can be made with low roughness suitable for contact recording, and can generate narrow readback pulses with large amplitude. Many aspects of Pd/Co performance, such as overwrite, can be predictably optimized for a given set of transducer properties. The reported results show that compositionally modulated structures can be made which have a wide variety of useful properties for perpendicular hard disk and magneto-optic recording.
On the Perpendicular Magnetic Anisotropy of Pt/Co Multilayers: Structure-Property Relationships
Authors: Bertero G. A. , Sinclair R.
Published: April 2011

A series of Pt/Co multilayers were sputter-deposited under various deposition conditions to promote structural changes resulting in marked differences in both the perpendicular anisotropy and magnetic coercivity. High resolution transmission electron microscopy was used in combination with other analytical techniques to study the structure of these films. It was found that the most important feature controlling the magnitude of the anisotropy is the interface sharpness. Conversely properties such as the quality of the (111) texture, grain shape or the defect structure, were found to be of secondary importance. The magnetic coercivity ranged from 0.6 to 7 kOe depending on the sputtering conditions and was found to depend strongly on the grain boundary structure rather than on the grain size.
Magnetic X-Ray Circular Dichroism in Fe Co Pt Multilayers
Authors: Tobin J. G. , Jankowski A. F. , Waddill G. D. , Sterne P. A.
Published: April 2011

Magnetic x-ray circular dichroism in x-ray absorption has been used to investigate the ternary multilayer system, Fe Co Pt. Samples were prepared by planar magnetron sputter deposition and carefully characterized, using a variety of techniques such as grazing-incidence and high-angle x-ray scattering, Auger depth profiling and cross-section transmission electron microscopy. As previously reported, the Fe9.5Å Pt9.5Å exhibits a large dichroism in the Fe 2p absorption. Interestingly while the Co9.5Å Pt9.5Å has no measurable dichroism, the Fe4.7Å Co4.7Å Pt9.5Å sample has a dichroism at both the Fe 2p and Co 2p absorption edges. These and other results will be compared to slab calculation predictions. Possible explanations will be discussed.
Texture and Grain Size of Permalloy Thin Films Sputtered on Silicon With Cr, Ta and SiO2 Buffer Layers
Authors: Galtier P. , Jerome R. , Valet T.
Published: April 2011

We have investigated the structural properties of Ni80Fe20 thin films sputtered on silicon with Cr, Ta and SiO2 buffer layers using transmission electron microscopy. We observe a decrease of the grain size when Ta and SiO2 underlayers are used instead of Cr. Permalloy films deposited on Ta layers are strongly (111) textured while those grown on Cr and SiO2 are mostly randomly oriented. The results are discussed with respect to the nanostructure of both Ta, Cr and SiO2 underlayers and in relation to the variation of the magnetic softness observed in this system.
Microraman Study of PbTiO3 Thin Film Prepared by Sol-Gel Technique
Authors: Ching-Prado E. , Reynés-Figueroa A. , Katiyar R. S. , Majumder S. B. , Agrawal D. C.
Published: April 2011

A PbTiO3 thin film prepared on silicon substrate by sol-gel technique has been studied by micro-Raman spectroscopy. The spectra, in comparison to the single crystal work, show high background in the low frequency region and Raman lines are broader, thus revealing the polycrystalline nature of the film. The frequencies of the Raman bands in the film are clearly shifted to lower frequencies compared to the corresponding ones in the single crystal or powder forms. This phenomenon is similar to the hydrostatic pressure effect on the Raman lines of PbTiO3 single crystal. The film, therefore, has grains under stress. This stress is caused by non-equilibrium defects and diffusion at the interface. Measurements at different film positions showed variation in the frequency and width of the Raman bands which are associated with the stress and grain size inhomogeneities. The measured shift in the Raman frequencies suggest grain sizes ≤l μm. XRD indicates grain size around 22 nm.
Micro-Mechanical Characterization of Tantalum Nitride Thin Films on Sapphire Substrates
Authors: Venkataraman Shankar K. , Nelson John C. , Moody Neville R. , Kohlstedt David L. , Gerberich William W.
Published: April 2011

The adhesion of Ta2N thin films – often used as thin film resistors – to sapphire substrates has been studied by continuous microindentation and microscratch techniques. Ta2N films, 0.1-0.63μm in thickness, were sputter deposited onto single crystal substrates. Continuous microscratch experiments were performed by driving a conical diamond indenter simultaneously into and across the film surface until stresses high enough to delaminate the film were developed. Continuous microindentation experiments were performed to induce film spallation by normal indentation. From both of these experiments, interfacial fracture toughness was determined as a function of film thickness. The interfacial fracture toughness obtained from continuous microscratch experiments is 0.53±0.17 MPa√m, independent of film thickness. This observation indicates that there is almost no plastic deformation in the film prior to fracture so that a ‘true’ interfacial fracture toughness is measured. For the 0.63 µm thick film, continuous microindentation data yielded a fracture toughness of 0.61 ±0.08 MPa√m, which matches closely the value obtained from the microscratch test. Hence, the continuous microscratch and microindentation techniques are viable methods for determining the interfacial fracture toughness in such bi-material systems.
Raman Characterization of Polycrystalline Silicon: Stress Profile Measurements
Authors: Benrakkad M. S. , Perez-Rodriguez A. , Jahwari T. , Samitier J. , Lopez-Villegas J. M. , Morante J. R.
Published: April 2011

Raman spectroscopy is applied for the analysis of polysilicon films deposited on SiO2 sacrificial layers. Different deposition technologies and processing parameters have been studied. The features of the first order Si Raman signal (shape, width and position of maximum) are analyzed in order to evaluate the stress average value in the scattering volume. MicroRaman measurements performed at different points on the edge of the samples allows the estimation of the stress gradient through the polysilicon layers. These measurements are correlated with the structure obtained by using micromachined test structures.
Tribological Properties of Laser Deposited SiC Coatings
Authors: Zehnder T. , Blatter A. , Burger J. , Julia-Schmutz C. , Christoph R.
Published: April 2011

We studied on a nanometer scale the tribological properties of thin silicon carbide films on Si(100) wafers and stainless steel. The coatings were fabricated from a sintered SiC target by pulsed ArF laser deposition at substrate temperatures between 20 °C and 1000 °C. Amorphous films resulted at low deposition temperatures while nanocrystalline structures developed at high deposition temperatures. An atomic force/lateral force microscope was employed to characterize the film topography and the friction behavior. The microhardness was determined from measurements utilizing a depth-sensing nanoindentation instrument. The SiC films on Si(100) exhibit a smooth surface with an average roughness Ra of a few nanometer, the amorphous films being even an order of magnitude smoother. No appreciable differences were found in microhardness and friction coefficient between amorphous and nanocrystalline films. On stainless steel, amorphous SiC coatings were obtained for deposition temperatures up to 500 °C. Their surface relief portrayed the grain boundaries of the underlying steel substrate, reflecting the ballistic nature of the deposition process. No stoichiometric films were obtained above 500 °C as the silicon from the growing film quickly dissolved in the steel substrate.
Mean Field Analysis of Orientation Selective Grain Growth Driven By Interface-Energy Anisotropy
Authors: Floro J. A. , Thompson C. V.
Published: April 2011

Abnormal grain growth is characterized by the lack of a steady state grain size distribution. In extreme cases the size distribution becomes transiently bimodal, with a few grains growing much larger than the average size. This is known as secondary grain growth. In polycrystalline thin films, the surface energy γs and film/substrate interfacial energy γi vary with grain orientation, providing an orientation-selective driving force that can lead to abnormal grain growth. We employ a mean field analysis that incorporates the effect of interface energy anisotropy to predict the evolution of the grain size/orientation distribution. While abnormal grain growth and texture evolution always result when interface energy anisotropy is present, whether secondary grain growth occurs will depend sensitively on the details of the orientation dependence of γi.
Energies and Atomic Structures of Grain Boundaries in Silicon: Comparison Between Tilt and Twist Boundaries
Authors: Kohyama M. , Yamamoto R. , Watanabe Y.
Published: April 2011

The energies and atomic structures of tilt and twist boundaries in Si have been examined by using the tight-binding electronic theory, and the reason why twist boundaries are seldom found in polycrystalline Si has been investigated. About the frequently observed {122} Σ=9 and {255} Σ=27 tilt boundaries, the configurations without any coordination defects consistent with the electron microscopy observations have relatively small interfacial energies with small bond distortions. About the <111> Σ=7, <011> Σ=3 and <001> Σ = 5 twist boundaries, the configurations contain larger bond distortions or more coordination defects, and much larger interfacial energies than those of the tilt boundaries. The <001> twist boundaries have very complex structures as compared with the other twist boundaries, which can be explained by the morphology of the ideal surfaces. The stability of the tilt boundaries in Si can be explained by the viewpoint of the stable structural units consisting of atomic rings.
Polycrystalline Grain Structure of Sputtered Aluminum Nitride Films
Authors: Matsuda Asher T , Liaw H. Ming , Cronin Wayne A , Tompkins Harland G , Fejes Peter L , Evans Keenan L
Published: April 2011

Reactively-sputtered, polycrystalline thin film aluminum nitride (AlN) is an attractive material for use in acoustic wave devices, for which it requires a strong preferred orientation, similar to that found in epitaxial films. This investigation evaluated the grain structure including preferred orientation, grain size, and surface morphology of sputtered A1N films. The characterization techniques utilized included x-ray diffraction (XRD), secondary ion mass spectroscopy (SIMS), transmission electron microscopy (TEM), and atomic force microscopy (AFM). The results revealed two types of grain structure: 1) a single-grain columnar structure that is perfectly oriented in the [001] direction throughout the entire film thickness and 2) a multiple-grain columnar structure that possesses a strong [001] orientation at the bottom of the film and a tilted [001] combined with other orientations at the top of the film. Strong correlations between orientation and surface morphology, oxygen content, and grain size were observed, namely higher degrees of c-axis orientation correlated with lower mean surface roughness values, reduced oxygen concentration, and narrower grains.
On the Relationship between Calculations and Measurements of the Free Volume of Grain Boundaries
Authors: Mehta S. C. , Smith D. A.
Published: April 2011

Grain boundary free volume, simply defined as the difference between the volume of a bicrystal and that of a single crystal containing an equal number of atoms, provides a good measure of average grain boundary coordination. Free volume is useful because (a) computer calculations suggest that the grain boundary free volume scales with the grain boundary energy and (b) experimental measurement of free volume may be relatively easier and more direct than that of grain boundary energy. The objective of this paper is to compare the predictions from computer models of grain boundary free volume with experimental measurements.
Characteristics of Sub-micron Polysilicon Thin Film Transistors
Authors: Olasupo Kola R , Hatalis Professor M. K.
Published: April 2011

The polysilicon thin film transistor has been actively studied for the large area display applications like active matrix liquid crystal displays and for load cell in static random access memories. Due to low effective carrier mobility in polysilicon, the circuit speed is limited. Since the circuit delay time is directly proportional to the square of the channel length, short channel TFTs will be advantageous for high speed applications. In this work, we have studied the current voltage characteristics of an inverted sub-micron P-channel polysilicon thin-film transistor with self-aligned LDD structure to obtain a well-controlled channel and drain offset lengths. The particular features we examined are the leakage current and mobility. The leakage current and the ON current were found to be in the picoamp and micro-amp range respectively for devices having channel length in the range of 1.0μm to 0.35μm. Even very small devices having L&W = 0.35μm × 0.35μm exhibited characteristics similar to wider devices. The on/off current ratio was in the order of 105 before hydrogenation.
Flat Panel Display Substrates
Authors: Moffatt Dawne M.
Published: April 2011

The performance of advanced flat panel displays is intrinsically linked to critical properties of the substrate material. In the manufacture of active-matrix liquid crystal displays (AMLCDs) and some emissive displays, there are certain process steps that require extreme conditions such as strong chemical washes and temperatures in excess of 600°C. As a result, the glass substrate used in these displays must be able to withstand these environments without degradation of its properties. It has become apparent that the flat panel display (FPD) manufacturers will benefit from substrates with improved acid durability, higher temperature capability, and thermal expansion coefficients consistent with other display materials.

This paper focuses on one of the less-understood features of the glass substrate: the expansion characteristics as a function of temperature. Thermal expansion is important as it affects the compatibility of the glass with display materials, which, in the case of AMLCDs and some silicon-microtip field emission displays (FED), require an expansion close to that of silicon. In addition, thermal breakage during processing is directly proportional to the expansion coefficient.

This study focused on the thermal expansion characteristics of two different FPD substrate glasses. The first one is code 7059, manufactured by Corning Incorporated and currently the standard in AMLCDs. A new substrate composition, Corning code 1737, with enhanced durability, temperature capability, and expansion tuned to the AMLCD applications will also be discussed.
Characterization Of Inorganic Contamination In Liquid Crystal Display Materials Using Total Reflection X-Ray Fluorescence (TXRF)
Authors: Hockett R. S. , Metz J. M.
Published: April 2011

This work is a feasibility study for using Total reflection X-Ray Fluorescence (TXRF) to characterize inorganic contamination at the surface of, and in, liquid crystal display materials as a function of their processing. Five samples were taken from process steps called: Cr black mask, Cr pattern, RGB pattern, topcoat, and ITO, all on glass substrates. TXRF, a glancing angle XRF technique, is sensitive to inorganic elements and can be used to detect inorganic contamination at surfaces. In addition, increasing the glancing angle can lead to penetration of thin films, and thereby to some qualitative depth information for the detected elements. Elements detected in this study included: Al, Si, S, Cl, In/Sn, Ca, Ba, Cr, Fe, Cu, Ni and Zn.
Effects of N2 Plasma Treatment on SiO2 Gate Insulator in a-Si:H Thin Film Transistor
Authors: Kim Sung Chul , Bae Sung Sig , Oh Eui Yeol , Kim Jeong Hyun , Lee Jong Wan , Kim Cha Yeon , Kim Donggil
Published: April 2011

We fabricated the high performance a-Si:H TFT using the N2 plasma treated APCVD SiO2 as a gate insulator. The effects of N2 plasma treatment on the APCVD SiO2 were investigated by XPS and SIMS measurements. And the formation of the oxynitride interface layer between a-Si:H and APCVD SiO2 was found in the a-Si:H TFT. From our experimental results, It may be concluded that most nitrogen atoms, which were incorporated by the exposure of SiO2 layer to N2 plasma, exist, not bonded to other atoms, near the surface of the SiO2 layer and during the sequential deposition of a-Si:H on the N2 plasma treated APCVD SiO2 layer Si-N bonds are formed, resulting in the oxynitride layer in the interface region. This explains the high performance a-Si:H TFT with the N2 plasma treated APCVD SiO2 gate insulator.
a-Si TFT Technologies for AM-LCDS
Authors: Ibaraki Nobuki
Published: April 2011

A technical trend for a-Si TFTs is their application to large-size, high-pixel density AMLCDs such as XGA, EWS, and HDTV. In order to realize these LCDs, the TFT device characteristics must be improved. Future technologies, which will be necessary to fabricate TFTs with improved characteristics are as follows,

(1) Fully self-aligned TFT technology: A SA-TFT structure reduces the feedthrough voltage caused by parasitic capacitance due to gate/source overlap. This results in an improved picture quality and a higher aperture ratio. Fabrication of such a structure would require ion doping technology.

(2) Ion doping technology: This non-mass-separated implantation technique has large area doping capability and much higher doping speed compared to conventional ion implantation technique. The major problems with the ion doping technique is the implantation of unwanted species which deteriorate the quality of source/drain and channel regions of TFTs.
Solid-State Luminescent Color Displays
Authors: Pope Edward J. A.
Published: April 2011

By the end of 1994, flat-panel displays for lap-top computers and televisions will exceed $4.0 billion in total sales. Currently, most such displays are based entirely upon an advanced liquid crystal technology requiring several precisely aligned LC layers. A new technology for flat-panel displays, based upon the solid-state luminescence of sol-gel derived microspheres has been proposed. Silica gel-derived microspheres can be prepared at near ambient temperatures, doped with either optically-active organic dye molecules or lanthanide ions. Microspheres doped to give red, blue, and green luminescence can be arranged in a pixel pattern to form the basis of a display screen. A single monochrome LC layer is used to modulate the excitation light, or pump source, that activates the fluorescence of each pixel.
Vector E-Field Probe for Testing Industrial Applicators.
Authors: Roussy Georges , Thiebaut Jean-Marie , Agbossou Kodjo , Dichtel Bernard
Published: April 2011

Using the modulated scatterer technique allows us to measure the electromagnetic field in an applicator. The design of a new sensor modulated at 25 Hz is described. The operating conditions and the performance are presented.

The sensor can be used for measuring high microwave electric fields up to 10 kV/m in an industrial applicator supplied by any industrial magnetron.
Dielectric Metrology VIA Microwave Tomography: Present and Future
Authors: Bolomey J.Ch. , Joachimowicz N.
Published: April 2011

Until now, the measurement techniques used for the dielectric characterization of materials require severe limitations in terms of sample shape, size and homogeneity. This paper considers the dielectric permittivity measurement as a non-linear inverse scattering problem. Such an approach allows to identify the quantities to be measured and suggests possible experimental arrangements. The problem is shown to be significantly simplified if the shape of the material is known and if some a priori knowledge of the averaged value of the permittivity in the material under test is available. Two test cases have been selected to illustrate the state of the art in solving such inverse problems. The first one consists of a two-dimensional configuration which is applicable to cylindrical objects, and the second one to a vector three-dimensional configuration applicable, for instance, to cubic samples. The main limitations of such an inverse scattering approach are discussed and expected improvements in the near future are analysed.
Novel Routes to Microwave Processing of Ceramic Materials
Authors: Willert-Porada M.
Published: April 2011

Material parameters important for microwave processing are identified in case of powder synthesis from precursor compounds and in case of sintering Al2O3- as well as SiC-matrix ceramics. By varying the spatial distribution of the precursor in microwave transparent materials, different pyrolysis temperatures are obtained, which can be attributed to different heating rates due to selective microwave heating. The microwave sintering behavior of oxide ceramics is strongly influenced by the specific surface area of the powder and by aliovalent dopants. In contrast, for covalent ceramics, like SiC+TiC, no experimental evidence for similar effects was obtained.
Microwave Absorption in NaCl Crystals with Various Controlled Defect Conditions
Authors: Meng Binshen , Booske John , Cooper Reid , Freeman Sam
Published: April 2011

A thorough understanding of fundamental microwave absorption mechanisms in ionic crystalline solids is important for microwave sintering of ceramics, as well as the design of high speed electronic packaging, advanced radomes, etc. Of particular importance to these applications are how the density and type of crystalline defects affect the dominant microwave absorption mechanisms. We have designed experiments to measure microwave absorption in NaCl samples with controlled variations in defect conditions(pure, point defects, dislocations and grain boundaries) at different temperatures (20–400 °C) and frequencies (2–20 GHz). Initial results are reported and discussed.
Transferring Micro Wa Ve-Assisted Technology to the Ceramic Industry
Authors: Wroe F.C.R.
Published: April 2011

Technology transfer is often described as the final stage in the process of technological change. This paper will attempt to demonstrate that this should not be the case, and technology transfer should be considered early in the development of any new technology. The paper will commence with a definition of technology, proceed to describe briefly the nature and effects of technological change and end with a description of how we hope to transfer microwave-assisted technology to the ceramic industry.
Microwave Radiation Effects on Ionic Current in Ionic Crystalline Solids
Authors: Freeman S. , Booske J. , Cooper R. , Meng B.
Published: April 2011

We describe experiments to test for microwave enhancement of bulk vacancy diffusion in NaCl, bulk interstitial diffusion in AgCl, and grain boundary diffusion in NaCl. Experimental results for bulk vacancy diffusion in NaCl indicate that intrinsic vacancy mobility is not enhanced by microwave field intensities typical of microwave sintering experiments. Nevertheless, a microwave effect is observed with features consistent with a recent theory for microwave-enhanced driving forces.
Experimental Observations of Thermal Spikes in Microwave Processing of Ceramic Oxide Fibers
Authors: Vogt Gerald J. , Unruh Wesley P. , Thomas J. R.
Published: April 2011

Microwave heating of alumina/silica fiber tows in a single-mode microwave cavity at 2.45 GHz has produced a surprising thermal spike behavior on the fiber bundles. During a thermal spike, a “hot spot” on the tow brightens rapidly, persists for a few seconds, and then rapidly extinguishes. A hot spot can encompass the entire tow in the cavity or just a localized portion of the tow. Some local hot spots propagate along the fiber. Thermal spikes are triggered by relatively small (<15%) increases in power, thus having obvious implications for the development of practical microwave fiber processing systems. A tow can be heated through several successive thermal spikes, after which the tow is left substantially cooler than it was originally, although the applied microwave electric field is much larger. X-ray diffraction studies show that after each temperature spike there is a partial phase transformation of the tow material into mullite. After several excursions the tow has been largely transformed to the new, less lossy phase and is more difficult to heat. Heating experiments with Nextel 550 tows are examined for a plausible explanation of this microwave heating behavior.
Microwave Vulcanization: A Lesson in Business and Technology
Authors: Krieger Bernard
Published: April 2011

Successful applications of microwave heating technology result from much more than successful engineering and pilot demonstration. Of utmost importance is translating this information into meaningful customer satisfaction through business concepts intrinsic to the industry being served. Microwave heating companies and laboratories are poorly positioned to commercialize new applications. They do not have the depth of experience in each of the industries which they serve. Success comes only from in-depth knowledge of real customer needs.

Microwave vulcanization of rubber is one of the very successful applications. This paper uses the Rubber Industry as an example of the type of thinking necessary to develop a “customer” focus as opposed to a “microwave” focus.
Microwave Pyrolysis of Emulsified Ceramic Precursor Ocompounds
Authors: Willert-Porada M. , Dennhöfer S. , Hachmeister D.
Published: April 2011

Application of paraffin as a MW-transparent matrix for microwave pyrolysis of metalorganic compounds enables synthesis of large quantities of nanosized powders with excellent storability and packing behavior. Fully crystalline, nanosized t-ZrO2 powders with specific surface area > 200 m 2 g -1 are obtained from Zr-alcoholate, and alumina powders with > 500 m2g-1 from Al-alcoholates. Some differences exist between microwave pyrolysis and conventional pyrolysis of such mixtures. Powders from microwave pyrolysis transform at lower calcination temperature to α-A12O3 and exhibit after calcination a more homogeneous morphology as compared to powders from conventional pyrolysis. Furthermore, a different composition of the volatile pyrolysis products is found. t-ZrO2 powder from the microwave processing route exhibits an increased stability towards transformation to monoclinic ZrO2 as well as smaller initial grain sizes than a conventionally synthesized powder.
Plasma Assisted Microwave Sintering and Joining of Ceramics
Authors: Samandi M. , Doroudian M.
Published: April 2011

Direct microwave sintering and joining of low temperature ceramics such as mullite have been extensively studied. However, it is recognised that microwave sintering and joining of high temperature oxide and non-oxide ceramics poses serious problems, primarily because of the difficulty of coupling microwave energy into these non-absorbing materials which make up the bulk of advanced ceramics. Attempts to overcome this problem by using indirect auxiliary heating or utilisation of intermediary or impure materials have been, by and large, unsatisfactory. Indeed, this fundamental physical barrier has seriously impaired the penetration of microwave heating in ceramic processing.

In order to overcome this seemingly insurmountable fundamental barrier, a radical approach is required. This has been recently achieved by using a Microwave Induced Plasma (MIP) whereby microwave energy is utilised in a hybrid fashion. In this method, a microwave plasma is used to rapidly heat the ceramic to temperatures at which it becomes absorbing. At this point, microwave radiation is directly coupled to the ceramic and the plasma is extinguished since energy is no longer available to ionise the gas and sustain a plasma. This hybrid approach circumvents the limitations of conventional microwave heating for sintering and joining of advanced materials. In this review paper the fundamentals of microwave/materials interaction and conventional approach to microwave heating of ceramics will be thoroughly discussed. In addition, the new hybrid heating developed by the authors will be described and the possibility of MIP-assisted sintering/joining of industrially important materials will be demonstrated.
Microwave Processing of Polymer Composites
Authors: Hawley Martin C. , Wei Jianghua , Adegbite Valerie
Published: April 2011

Microwave processing has been investigated as an alternative to conventional thermal method in processing polymer matrix composite materials. The main advantages of microwave processing over thermal processing are that: 1) microwave heating is volumetric, direct, selective, instantaneous, and controllable which offers advantages such as fast heating and minimization of temperature excursion; 2) microwave radiation can provide many desirable features in polymer and composite processing, such as enhanced polymerization rates and glass transition temperatures of thermosets, improved mechanical properties of composite materials, and increased adhesion between graphite fibers and matrix.

Microwave heating has been used in food processing, drying, material processing, waste treatment, and organic synthesis. This paper summarizes the current status of microwave technology for the processing of polymer matrix composite materials. The discussion will be focused on the use and development of batch and continuous techniques using tunable single mode resonant microwave cavities for processing polymer composites.
Microwave Processing of Polyimide Thin Films
Authors: Lewis David A. , Lamaire Susan J. , Nunes Thomas
Published: April 2011

Microwave processing has been used to reduce the long process cycles normally associated with the curing cycles for highly ordered polyimides, such as BPDA-PDA. These materials have found applications in the electronics industry due to the excellent thermal stability and low coefficient of thermal expansion of this class of polymers. Thin polymer films - an application not normally considered for microwave curing - were processed and the dependence of the mechanical properties compared with conventional thermal processing.
Reactive Poly(Arylene Ether) Toughening of Cyanate Ester Networks Via Thermal and MicrowaveCuring
Authors: Srinivasan S. A. , Joardar S. S. , Priddy D. B. , Ward T. C , Mcgrath J. E.
Published: April 2011

Cyanate ester networks are receiving considerable attention as potential candidates for high temperature adhesives and composite applications. The dicyanates ester monomers cyclo-trimerize1,2 via addition polymerization to form highly crosslinked polycyanurates (Scheme 1).
Dielectric Analysis Of Semi-Crystalline Poly(Ethylene Terephthalate)
Authors: Wei Jianghua , Delgado Richard , Hawley Martin C. , T.Demeuse Mark
Published: April 2011

Dielectric properties of poly(ethylene terephthalate) (PET) were measured over a frequency range of 10 KHz to 2.45 GHz and a temperature range of 20 to 110°C. Relaxation peaks were identified at 1) fixed frequency with variable temperatures, and 2) fixed temperature with variable frequencies. The crystallinity of poly (ethylene terephthalate) was measured using differential scanning calorimetry (DSC). Relationships between crystallinity, dielectric properties, and location of the dielectric relaxation peak on the frequency and temperature scales were studied for poly(ethylene terephthalate). Also, the dielectric loss factor decreases with increased crystallinity at 2.45 GHz and 4 GHz within the temperature range studied.
Use of High-Power Traveling Wave Tubes as a Microwave Heating Source
Authors: Everleigh C. A. , Johnson A. C. , Espinosa R. J. , Garard R. S.
Published: April 2011

This paper reports on the use of high-power traveling wave tubes (TWTs) as a source of microwave energy for materials processing applications. Recent work by Oak Ridge National Laboratories and Microwave Laboratories personnel has demonstrated the usefulness of sweeping the microwave processing frequency over substantial (>20%) bandwidths in order to achieve uniformity of heating over volumes unattainable using conventional microwave sources ∼ e.g., magnetrons. Properly constructed high-power TWTs are a logical choice of microwave source in such systems. After briefly reviewing the basic operating principles of the TWT, the required characteristics of a TWT for materials processing applications and how those requirements affect the TWT's design are discussed. Comments on the present product lines and areas of development for all of the major TWT manufacturers are also presented. Finally, the issue of the ultimate potential cost of TWTs designed for microwave processing applications is addressed.
Crystal Growth and Scintillation Properties of CeF3
Authors: Allain J.L. , Couchaud M. , Ferrand B. , Grange Y. , Utts B. , Wyon Ch.
Published: April 2011

Large single crystals of CeF3, 40 mm in diameter up to 140 mm in length, have been grown using the vertical Bridgman technique. Their optical and scintillation properties and their radiation hardness have been measured.
Cerium-Doped Yttrium Aluminum Perovskite (Yap): Properties of Commercial Crystals
Authors: Trower W. Peter
Published: April 2011

The journey of YAP from interesting laboratory curiosity to a material with commercial possibilities has taken two full decades. The reported YAP properties which motivated this effort are its rapid (~ 27 ns) dominant (~ 97%) decay which results in negligible afterglow; high density (~ 5.55 g/cm3); brightness (~ 50% of NaI:Tl); energy resolution (~ 6% at 455 keV); physical ruggedness; and chemical nonreactivity. Lone among its draw backs as a practical scintillator is its emission which is centered in the UV (~ 350 nm). Three firms now offer YAP crystals of sufficient size and quality that industrial applications are becoming possible.

To date, the physical properties of YAP have only been published on small laboratory samples. Here we report a comprehensive and comparative evaluation of physical properties of material from all known commercial sources. Further, we speculate on the physical origin of variations among samples. Finally, we attempt to predict what can ultimately be expected from YAP as further refinements in its processing techniques are perfected.
Scintillating Glass Fiber-Optic Neutron Sensors
Authors: Abel K.H. , Arthur R.J. , Bliss M. , Brite D.W. , Brodzinski R.L. , Craig R.A. , Geelhood B.D. , Goldman D.S. , Griffin J.W. , Perkins R.W. , Reeder P.L. , Richey W.C. , Stahl K A. , Sunberg D.S. , Warner R.A. , Weber M. J. , Wogman N.A.
Published: April 2011

Pacific Northwest Laboratory (PNL) has fabricated cerium-activated lithium silicate scintillating fibers via a hot-downdraw process. These fibers, which, as produced, typically have a transmission length (e−1 length) of greater than 2 meters, are found to undergo aging when subjected to room air. The aging, which is complete in a few weeks, reduces the transmission length to the order of 0.5 meter. Because of the high alkali content of the glass (on the order of 20-30 mole % lithia), we have attributed this aging to aqueous corrosion at the polymer cladding/glass interface. Changes in transmission with chemical treatment of the surface support the corrosion model. Fiber transmission performance has been preserved by modifying the hot-downdraw to a double crucible to produce glass-on-glass waveguides.
Activation of Lead Fluoride Room Temperature Luminescence by Structural Modifications
Authors: Alov D.L. , Bazhenov A.V. , Egorov V.K. , Emelchenko G.A. , Klassen N.V. , Kolchin A.A. , Kondakov S.F. , Kulakov A.B. , Mahonin S.I. , Prokopenko V.M. , Rybchenko S.I. , Savchenko I.B. , Sinitzin V.V. , Soloviev A.V. , Shmyt'ko I.M. , Shmurak S.Z.
Published: April 2011

The connection of lead fluoride luminescence properties with its structural characteristics has been studied. Single crystals of the cubic and orthorombic phases, cubic and orthorombic powders, pressure compacted orthorombic ceramics, plastically deformed crystals were used. The photo- and X-ray excited luminescence spectra have been investigated. The experimental results have shown that the room temperature luminescence of lead fluoride can be accounted for local light emitting centers which are produced by the intrinsic structural defects in the orthorombic lead fluoride.
Crystal Detectors in Particle Physics
Authors: Newman Harvey B. , Gratta Giorgio , Zhu Ren-yuan
Published: April 2011

We review the principal characteristics driving the design of precision calorimeters composed of inorganic crystal scintillators now in operation (L3, CLEO II) or developed for the next generation of particle physics experiments. The unique discovery potential of these detectors (1.5 to 50 m3of crystals; 104to > 105elements) is the result of their high electron and photon energy resolution over a wide energy range, uniform hermetic acceptance and fine granularity.

Experiments at CERN's multi-TeV Large Hadron Collider (LHC) will search for the Higgs particles thought to be responsible for mass, and for many other new physics processes. In order to exploit the intrinsically high resolution of crystal detectors, exceptionally high speed (1 to 30 ns decay time) and radiation resistance are required. BaF2and CeF3are currently the preferred choices, and higher density alternatives such as PbWO4are under investigation.

Lower energy, high luminosity experiments that will measure rare particle decays, and explore the violation of the fundamental “CP” symmetry that may be related to the predominance of matter over antimatter in our universe, have chosen Cesium Iodide for its combination of high light output, speed, and radiation resistance.

Recent developments by Caltech include the use of photons generated by anH−beam from an RFQ accelerator to calibrate and provide sub-percent resolution in the L3 BGO calorimeter, and anin situoptical bleaching technique that renders large BaF2crystals now mass produced in China radiation hard up to dose levels ≳l 10 MegaRads.