bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chemical Effects of substrate Temperature and Feed Gas Composition on Ion Beam Deposited AlN and AlN:H
Authors: Huang L. , Wang X. D. , Hipps K. W. , Mazur U. , Dickinson J. T. , Heffron R. 
Published: April 2011

AbstractDirect ion beam sputter deposition of alN is studied using both pure nitrogen and a 75% N2/25% H2 mixture as the feed gas for the ion gun. the chemical characteristics of these films are probed using infrared spectroscopy and chemical etching. the presence of al-N2 species is associated with reactive and highly defective films. the presence of NHX species increases by several orders of magnitude the rate at which alN film are etched by base. However, stoichiometric and low defect alN films prepared by depositing alN:H onto substrates heated to 200 °C have reactivities similar to the best alN films produced in the absence of hydrogen.
Conductance Measurements of Thermally Annealed, Si-Implanted Quartz
Authors: R.Hodges Alex , Farlow Gary C. 
Published: April 2011

AbstractPreliminary conductance measurements of Si implanted, α-Quartz which had been annealed in ar to 1000• C have been made using a bridge method. the quartz was implanted to a dose expected to yield Si precipitates inside the quartz upon annealing. the measured conductivity, based on a geometry deduced from TRIM calculations and several trans-conductance measurements, is ~ 2 х 10-4(Ω m)-1. This is consistent with large islands of Si in series with an insulating matrix.
Thin Film Polymer Stress Measurement Using Piezoresistive Anisotropically Etched Pressure Sensors
Authors: Monk David J. , Shah Mahesh 
Published: April 2011

ABSTRACTStresses in thin polymer films have been studied for some time by using wafer bowing, bending beams, microstructure release, and laser holographic techniques. An alternative technique for measuring stresses in thin films is discussed in the following paper. Piezoresistive anisotropically etched single crystal silicon pressure sensors are sensitive not only to applied pressure, but also to applied package stress. Deposited passivation materials, like silicone gels and polyimides, have been observed to change the sensitivity of the pressure sensor. In the current work, a thin, conformal polymeric coating (parylene C) is being developed for these pressure sensors. This thin film has been observed to reduce the sensitivity of the device as a function of the film thickness and modulus and the silicon thickness and modulus. The parylene C thin films exhibit a consistent change in film stress during annealing indicating a modification to polymer crystallinity and a corresponding change in material properties. Qualitatively, the electrical output on the pressure sensor compares favorably with measurements taken using wafer bowing. Experimental DMA and TMA work has been performed to determine the modulus (7.84 × 105 psi) and CTE (39 ppm/°C at 25 °C) of the material. However, literature values of modulus (4.1 × 105 psi) have been used with finite element analysis to model the stress effect more accurately for the thin conformal coating on the pressure sensor device. These results indicate that the sensitivity of the pressure sensor will be reduced approximately quadratically as a function of the polymer coating thickness. An empirical function has been derived to estimate sensitivity loss as a function of substrate (i.e., initial diaphragm material) modulus and thickness and coating modulus and thickness.
Characterization of Films Formed during the Corrosion of Copper in Dilute Solutions of Cupric Chloride
Authors: Walsh L. H. , Feilchenfeld N. B. 
Published: April 2011

ABSTRACTMicrostructural differences in copper deposited by four techniques commonly used in the microelectronics industry were previously reported. Grain size, preferred orientation, and near surface chemistry were considered. [1] Prediction of the reaction rates were made based on these differences and then correlated with actual measurements. [2] In aerobic conditions the grain size dictated the reaction rate, the smaller the size the faster the rate.[3] The composition of the surface film formed during etching was examined. The trends in chemical concentrations on the surface film vary for each sample, but the relative constituent amounts correlate to the grain size of the original copper samples. Thus, there is further evidence that during exposure to aqueous solutions of cupric chloride, copper corrosion, in terms of both etch rate and film composition, is dictated by grain size of the original copper and not other microstructural factors.
High Thermal Conductivity Graphite Copper Composites with Diamond Coatings for Thermal Management Packaging Applications
Authors: Stoessel Chris H. , Pan C. , Withers J. C. , Wallace D. , Loutfy R. O. 
Published: April 2011

ABSTRACTHigh thermal conductivity heat sinks for thermal management in electronic packaging is enabling to a variety of advanced electronic applications. Heat sinks in industrial semiconductor application have thermal conductivities generally less than 180 W/mK, and frequently have large expansion mismatch with chips such as silicon and gallium arsenide. A unique technology of producing graphite fiber reinforced copper (Cf/Cu) composite has been developed that produced thermal conductivities up to 454 W/mK utilizing a K=640 W/mK fiber reinforcement (with a potential for 800 W/mK when utilizing a K = 1100 W/mK P130 fiber) and thermal expansion that can be matched to chip materials. The process consists of utilizing a hollow cathode sputtering process to deposit a bonding layer followed by copper on spread graphite fibers, which are then consolidated into composites with architectures to achieve desired thermal conductivity and thermal expansion. The copper thickness determines graphite fiber loading up to 80 %. In heat sink applications, where the electrical conductivity of the graphite fiber reinforced copper composite is a problem, processing has been developed for applying electrically insulating diamond film, which has high thermal conductivity and acts as a heat spreader.
Wetting Behaviors of Sn-Based Solders on Cu and Pd Surfaces
Authors: Kim H. K. , Wang Y. , Maheshwari A. , Tu K. N. 
Published: April 2011

ABSTRACTWe have studied the surface morphology and wetting reaction of eutectic SnBi, eutectic SnPb, and pure Sn on Cu and Pd surfaces. In the case of Pd, the reactions were so fast that no quasi-equilibrium wetting angle could be measured. The compound formation has changed not only the interfaces but also the surfaces. Due to the formation of a reaction band outside the solder cap, the SnPb solder is no longer wetting the Cu surface but rather the Cu-Sn compound surface. In the wetting interface between eutectic SnPb and Cu, the morphology of the scallop-like Cu-Sn compound grains shows that we may not apply the classical model of layered compound growth to analyze the rate of soldering reactions.
The Use of Secondary Ion Mass Spectrometry to Investigate Wire Bonding Yield Problems on Gold Contacts
Authors: Mount G. R. , Walzak T. L. , Koo Y. C. , McClure D. 
Published: April 2011

ABSTRACTWith ongoing demand for high density wiring and high I/O on VLSI chips, the requirement of high wire bond yield is a challenge to achieve low cost, high performance and reliable products. Secondary Ion Mass Spectrometry (SIMS) was used to investigate the metallurgical contaminants on the gold wire bond pads and their impact on wire bond yields. SIMS depth profile studies showed that copper and nickel in concentrations greater than 1 wt% caused poor wire bondability, while copper concentration at less than 0.1 wt% resulted in good bondability of Al ultrasonic wire bonded to the gold pads.
Fabrication of Er Doped Glass Films as Used in Planar Optical Waveguides
Authors: Gates J. V. , Bruce A. J. , Shmulovich J. , Wong Y. H. , Nykolak G. , Barros M. R. X. , Ghosh R. 
Published: April 2011

AbstractSilica integrated optical circuits are expanding in functionality to include optically active waveguides. Traditionally, the planar optical waveguide structures include silica based glass films such as thermal oxides, phosphorous, and boron-phosphorous doped glasses. Various efforts have successfully doped conventional waveguides with Er, typically by solution doping. Material issues such as rare earth solubility and glass structure dictate that efficient optical amplifiers based on such waveguides have path lengths in excess of 10–15 cm. We have developed an alternative strategy using Er-doped soda-lime silicate glass films on silicon. The waveguide processing utilizes methods of deposition similar to those used in silicon IC technology, with modificatons in the compositions and thicknesses. In these glasses the effective solubility limits are relaxed and we have successfully fabricated short path length devices which demonstrate net gain of more than 4 dB/cm. Short path length devices offer a potential advantage in highly integrated multi-channel devices and offer an additional building block in system architectures.
Characterization of Magneto-Optical Rare Earth-Doped Ingaasp Thin Films on InP
Authors: Stadler B. J. , Vaccaro K. , Davis A. , Martin E. A. , Ramseyer G. O. , Lorenzo J. P. 
Published: April 2011

AbstractWe have investigated the properties of rare earth-doped InGaAsP thin films with special interest in magneto-optical device applications. Magneto-optical properties have been used in optical systems as isolators, waveguides, and switches. These materials and devices can be used to expand the functionality of InP opto-electronic integrated circuits (OEICs). Thin films of InP, InGaAs, and InGaAsP, grown by liquid phase epitaxy, were lattice matched to the (100) InP substrates. The films were n-type, with the carrier concentration decreasing by an order of magnitude in the doped films due to gettering by the rare earth elements. The doped films contained 2.6×1018 - 1.5×1020 cm−3 rare earth elements, which were observed to segregate toward the film/melt interface in the more highly doped films. A broad photoluminescence was observed at 1.52 μm in the Er-doped films. The Verdet constant was measured through the sample thickness, and the substrate signal dominated the measurements. However, the measured values were in agreement with published values for InP, which gives an indication of the films' host value. The Verdet constants increased from 4 to 7 deg/T/mm as the wavelength decreased toward the band edge. The band edges of our samples were 0.93, 1.62, and 1.30 μm, respectively. Rare earth dopants were observed to raise the refractive index of the InP films, and waveguiding at 1.3 μm was achieved in the rare earth-doped InP films and in the InGaAsP films.
In-Vivo Degradation of a Poly(Propylene-Fumarate) Biodegradable, Particulate Composite Bone Cement
Authors: Frazier Daveed D. , Lathi Vijay K. , Gerhart Tobin N. , Altobelli David E. , Hayes Wilson C. 
Published: April 2011

AbstractWe have developed a biodegradable particulate composite bone cement consisting of a poly(propylene glycol-fumarate)-(methylmethacrylate) matrix mixed with calcium carbonate and tricalcium phosphate particulates. Previous ex-vivo studies suggest that this system provides sufficient strength for a number of potential clinical applications including structural reinforcement of osseous defects, supplementation of internal fixation of age-related fractures, and delivery of antibiotics to treat osteomyelitis. Ex-vivo degradation assays have also shown that the cement approximates physiologic conditions of bone remodeling as it degrades. In order to evaluate the in-vivo responses to this material, we implanted cement specimens subcutaneously in rats for up to 84 days. Compressive strength of the subcutaneous implants increased linearly through day 21 to 4.91 MPa, then decreased linearly by day 84 to less than 1 MPa. We conclude that this PPFMMA system is biocompatible and biodegradable, and has the potential for use as an orthopedic bone cement. Future studies will be directed toward characterizing the intraosseous histological response and at coordinating the rate of cement degradation with bony ingrowth.
Wear Evaluation of Ultra High Molecular Weight Polyethylene Using Pin-On-Flat and Hip Simulation Techniques
Authors: Schroeder David W. , Higgins Joel C. 
Published: April 2011

AbstractReduction of wear and wear debris is one of the most important areas of research presently in the field of orthopedic devices. It is speculated that wear debris is one of the contributing factors in the cascade of events that lead to osteolysis. In this regard it is very important to be able to evaluate in vitro the wear of UHMWPE produced by various manufacturing methods. Presently the three most common methods of wear testing are: pin-on-flat, pin-on-disk, and hip simulator.Wear evaluation was performed on gamma irradiated UHMWPE that was manufactured by three different processes: extrusion, direct compression molding, and isostatic compression molding. The wear evaluation consisted of pin-on-flat and hip simulator testing.omparison of the results from these two different types of tests show that the two tests would rank the wear resistance of the UHMWPE in the same order. However, there is a variation in the difference of the wear rates between the two tests. The pin-on-flat results show that the direct and isostatic compression molded material had approximately 50% less wear than the extruded material whereas the hip simulator results show that the isostatic compression molded material had 16% less wear than the extruded material. The difference in the results of these two tests are the effects of a combination of factors including the mechanical and material properties of the UHN4WPE, modes of wear that are active, the state of stress (constant vs. cyclic) in the specimens, third body contamination of the lubricant, bacterial degradation of the bovine serum lubricant, etc. Both tests are very important and necessary in the evaluation of wear of orthopedic materials.
Bioactive Molecules Delivered by Ceramic Nanoparticles Coated with a Film of Polyhydroxyl Oligomers
Authors: Kossovsky Nir 
Published: April 2011

AbstractThe structural denaturation of polypeptides and other macromolecular pharmaceuticals upon surface adsorption from an aqueous environment is almost inevitable. Molecular denaturation, coupled with a net increase in entropy, accounts for the net negative ΔG and frequent irreversible nature of surface adsorption. The consequence of this interaction is that surface immobilized drugs lose their dynamic freedom and thus, all too often, their biological activity.This phenomenon has complicated the development of drug delivery vehicles. In this communication, a drug delivery system based on a novel surface modification process to help reverse the constraining activity of surfaces is described. Beginning with preformed carbon ceramic nanoparticles and self-assembled calcium-phosphate dihydrate particles (colloidal precipitation) to which glassy carbohydrates are then allowed to adsorb as a nanometer thick surface coating, a molecular carrier is formed. The carbohydrate coating functions as a dehydroprotectant and stabilizes subsequently non-covalently bound immobilized members of biochemically reactive surface members such as pharmaceuticals.Many of the physical properties of this enabling system have been characterized in vitro and in animal models. Antigen delivery, drug delivery, and enzyme stabilization experiments are described.
Growth Kinetics and Structural Quality in GaN Epitaxy by Low Pressure MOVPE
Authors: Briot O. , Alexis J.P. , Gil B. , Aulombard R.L. 
Published: April 2011

ABSTRACTGaN epilayers have been grown using low pressure MOVPE (76 Torr) onto (0001) sapphire substrates. Triethylgallium (TEGa) and Ammonia (NH3) were used as precursors. The growth rate has been determined versus growth parameters. The growth rate versus NH3 flow displays a rather unusual behavior, in particular at low growth temperature (buffer layer), where the growth rate decreases strongly when the NH3 flow increases. A growth mechanism involving a competitive adsorption step onto the surface is proposed, and results in a strong dependence of the growth rate on the V/III ratio.The structural quality of the layers has been assessed by X-ray diffraction versus the growth parameters, and will be reported here. A substrate nitridation step, prior to buffer layer deposition has been introduced in our growth process. The effect of substrate nitridation on the structural and optical properties of the epilayers is studied and we propose an optimized pre-treatment for the MOVPE growth of GaN onto (0001) sapphire substrates.
A Study of the Effect of Growth Rate and Annealing on GaN Buffer Layers on Sapphire
Authors: Ramer J.C. , Zheng K. , Kranenberg C.F. , Banas M. , Hersee S.D 
Published: April 2011

ABSTRACTUsing atomic force microscopy (AFM) and X-ray diffraction (XRD) we have determined that on [0001] oriented sapphire, the GaN buffer layer shows a degree of crystallinity that is dependent on growth rate. Annealing studies show evolution of the crystallinity and the emergence of a preferred orientation. Also, substrate orientation is found to influence the buffer layer crystallinity. Based on this work and previous results, we propose that the GaN buffer layer growth can be described by the Stranski-Krastanov growth process.
AlN Films Deposited by LP-MOCVD Atomic Layer Deposition at Lower Temperatures Using DMEAA and Ammonia
Authors: Kidder J.N. , Kuo J. S. , Pearsall T.P. , Rogers J.W. 
Published: April 2011

ABSTRACTWe have investigated the deposition of AlN thin films on Si(100), Al2O3(0001), and Al2O3(0112) substrates at lower temperatures (523–723 K) using a novel aluminum source, dimethylethylamine:alane (DMEAA), with ammonia as a nitrogen source in a low-pressure MOCVD atomic layer growth process. At reactor pressures of 25 and 50 Torr a four-step sequence of reactant flow steps separated by flush steps was cycled. We observed a tendency toward a self-limiting growth rate as the DMEAA step flow time was increased. The deposition uniformity was observed to be dependent on temperature and non-uniform deposition occurred at higher temperatures. The microstructure and crystalline orientation were examined using x-ray diffraction and crystalline A1N films were deposited at temperatures as low as 573 K. Crystallite size decreased with substrate temperature and at 523 K. amorphous films were deposited. At T > 650 K preferentially oriented crystalline films were deposited with orientations of Si(100)//AIN(0001), Al2O3(0001)//AIN(0001), Al2O3(0112)//AIN(1120).
Facets Formation Mechanism of GaN Hexagonal Pyramids on Dot-Patterns via Selective MOVPE
Authors: Hiramatsu Kazumasa , Kitamura Shota , Sawaki Nobuhiko 
Published: April 2011

ABSTRACTThree-dimensional GaN pyramids have been successfully obtained on dot-patterned GaN(0001)/sapphire substrates by using the selective MOVPE technique. The dot-pattern is a hexagon arranged with a 5μm width and a 10μm spacing. The GaN structure comprises a hexagonal pyramid covered with six {11ȃ01} pyramidal facets on the side or a frustum of a hexagonal pyramid having a (0001) facet on the top. The facet formation mechanism has been investigated by observing the facet structure with the growth time. The {11ȃ01} facets are very stable during the growth. The (0001) facet growth is dominant at the initial growth but almost stops at a certain growth time and then the facet structure is maintained. The appearance of the self-limited (0001) facet is attributed to the balance of flux between incoming Ga atoms from the vapor phase to the (0001) surface and outgoing Ga atoms from the (0001) surface to the {11ȃ01} surface via migration. The longer the diffusion length of the Ga atoms on the (0001) surface is, the more the surface migration is enhanced, resulting in the appearance of the wider (0001) facet on the top.
New Buffer Layers for GaN on Sapphire by Atomic Layer and Molecular Stream Epitaxy
Authors: Piner E.L. , He Y.W. , Boutros K.S. , Mcintosh F.G. , Roberts J.C. , Bedair S.M. , El-Masry N.A. 
Published: April 2011

ABSTRACTThe current approach of depositing a low temperature then annealed AlN or GaN buffer for the growth of GaN on sapphire results in a high dislocation density. These dislocations thread through the GaN layer to the surface. Reducing their density either by growing thicker films or using a strained layer superlattice is ineffective. Two new approaches for AlN/GaN buffer layer growth for GaN on sapphire have been employed: Atomic Layer Epitaxy (ALE) and Molecular Stream Epitaxy (MSE). ALE is distinguished by organo-metallic/ammonia separation while MSE is distinguished by cyclic annealing of the growing film. Both ALE and MSE enhance two dimensional growth of single crystal GaN on sapphire. The structural quality of epitaxial GaN grown on these buffer layers was studied by transmission electron microscopy (TEM) and x-ray diffraction (XRD). The initial result for the ALE buffer shows an improved quality GaN film with lower defect densities. The MSE grown buffer layer closely resembles that of conventionally grown MOCVD buffer layers observed by others, with dislocations threading through the GaN epilayer. The effects of these buffer layers on the structural and optical properties of GaN grown on sapphire will be presented.
Epitaxial Growth of AlN Thin Films on Silicon and Sapphire by Pulsed Laser Deposition
Authors: Vispute R.D. , Wu H. , Jagannadham K. , Narayan J. 
Published: April 2011

ABSTRACTAIN thin films have been grown epitaxially on Si(111) and Al2O3(0001) substrates by pulsed laser deposition. These films were characterized by FTIR and UV-Visible, x-ray diffraction, high resolution transmission electron and scanning electron microscopy, and electrical resistivity. The films deposited on silicon and sapphire at 750-800°C and laser energy density of ∼ 2 to 3J/cm2 are epitaxial with an orientational relationship of AIN[0001]║ Si[111], AIN[2 110]║Si[011] and AlN[0001]║Al2O3[0001], AIN[1 2 1 0]║ Al2O3[0110] and AIN[1010] ║ Al2O3[2110]. The both AIN/Si and AIN/Al2O3 interfaces were found to be quite sharp without any indication of interfacial reactions. The absorption edge measured by UV-Visible spectroscopy for the epitaxial AIN film grown on sapphire was sharp and the band gap was found to be 6.1eV. The electrical resistivity of the films was about 5-6×l013Ω-cm with a breakdown field of 5×106V/cm. We also found that the films deposited at higher laser energy densities ≥10J/cm2 and lower temperatures ≤650°C were nitrogen deficient and containing free metallic aluminum which degrade the microstructural, electrical and optical properties of the AIN films
Hydrogen, Acceptors, and H-Acceptor Complexes in GaN
Authors: Bosin Andrea , Fiorentini Vincenzo , Vanderbilt David 
Published: April 2011

ABSTRACTWe present ab-initio calculations on energetics and geometries of atomic hydrogen, of several candidate acceptors, and of H-acceptor complexes in wurtzite GaN For the H-Mg complex in Mg-doped GaN, we calculate the vibrational frequencies of H. Hydrogen is found to be a negative-U center. H-acceptor complex formation is always exothermic. Substitutional Be has a low formation energy and a shallow impurity level, which makes it a good candidate for p-doping in MBE growth. CN appears not to be shallow. Atomic hydrogen incorporation in undoped GaN is disfavored in an H2 atmosphere; it becomes favorable in p and n-type conditions in atomic H environments.