bluuebunny/crossref_metadata_2025_split huggingface dataset:
Integration of InGaN-based Optoelectronics with Dissimilar Substrates by Wafer Bonding and Laser Lift-off
Authors: Wong William S. , Kneissl Michael , Treat David W. , Teepe Mark , Miyashita Naoko , Johnson Noble M. 
Published: April 2011

ABSTRACTInGaN-based optoelectronics have been integrated with dissimilar substrate materials using a novel thin-film laser lift-off process. By employing the LLO process with wafer-bonding techniques, InGaN-based light emitting diodes (LEDs) have been integrated with Si substrates, forming vertically structured LEDs. The LLO process has also been employed to integrate InGaN-based laser diodes (LDs) with Cu and diamond substrates. Separation of InGaN-based thin-film devices from their typical sapphire growth substrates is accomplished using a pulsed excimer laser in the ultraviolet regime incident through the transparent substrate. Characterization of the LEDs and LDs before and after the sapphire substrate removal revealed no measurable degradation in device performance.
Fabrication of Three-Dimensional Photonic Crystal by Wafer Fusion Approach
Authors: Yamamoto Noritsugu , Tomoda Katsuhiro , Noda Susumu 
Published: April 2011

ABSTRACTBased on a set of requirements identified for photonic crystals intended for use in optoelectronic devices, we have developed a method of fabricating three-dimensional photonic crystals that involves stacking air/semiconductor gratings by wafer fusion approach. Precise alignment of the stacked layers is achieved through the use of a laser beam assisted very precise alignment system, and three-dimensional photonic crystal has been successfully fabricated for the infrared and optical communication wavelength regions. We have also developed a photonic crystal waveguide providing sharp 90° bend.
Synthesis and Luminescent Properties of GaN and GaN-Mn Blue Nanocrystalline Thin-Film Phosphor for FED
Authors: Bondar Vyacheslav D. , Felter Thomas E. , Hunt Charles E. , Kucharsky Igor Yo. , Chakhovskoi Andrei G. 
Published: April 2011

AbstractThe technologies of fabrication of thin film phosphors based on gallium nitride using rf-magnetron sputtering are developed and the structural properties of these films are studied. Luminescence and electron spin resonance (ESR) spectra of GaN and GaN-Mn thin films are obtained. A correlation between cathodo-luminescence intensity and conductivity of GaN films is found. The nature of emission centers in GaN and GaN-Mn thin films is discussed and a mechanism of luminescence in these films is proposed.
Zinc Oxide Thin Films Deposited by RF Magnetron Sputtering on Mylar Substrates at Room Temperature
Authors: Fortunato Elvira , Nunes Patrícia , Marques António , Costa Daniel , Águas Hugo , Ferreira Isabel , Costa Maria E. V. , Martins Rodrigo 
Published: April 2011

AbstractAluminium doped zinc oxide thin films (ZnO:Al) have been deposited on polyester (Mylar type D, 100 μm thickness) substrates at room temperature by r.f. magnetron sputtering. The structural, morphological, optical and electrical properties of the deposited films have been studied. The samples are polycrystalline with a hexagonal wurtzite structure and a strong crystallographic c-axis orientation (002) perpendicular to the substrate surface. The ZnO:Al thin films with 85% transmittance in the visible and infra-red region and a resistivity as low as 3.6×10−2 ωcm have been obtained, as deposited. The obtained results are comparable to those ones obtained on glass substrates, opening a new field of low cost, light weight, small volume, flexible and unbreakable large area optoelectronic devices.
Image Acquisition Using Non-Pixeled Amorphous Silicon Based Sensors
Authors: Fernandes M. , Vygranenko Yu. , Martins J. , Vieira M. 
Published: April 2011

AbstractWe suggest to enhance the performance of image acquisition systems based on large area amorphous silicon based sensors by optimizing the readout parameters such as the intensity and cross-section of scanner beam, acquisition time and bias conditions. The main output device characteristics as image responsivity, signal to noise ratio and spatial resolution were analyzed in open circuit, short circuit and photodiode modes. The result show that the highest signal to noise ratio and best dark to bright ratio can be achieved in short circuit mode.It was shown that the sensor resolution is related to the basic device parameters and, in practice, limited by the acquisition time and scanning beam properties. The scanning beam spot size limits the resolution due to the overlapping of dark and illuminated zones leading to a blurring effect on the final image and a consequent degradation in the resolution.
Long-Pulse Duration Excimer Laser Processing in the Fabrication of High Performance Polysilicon TFTs for Large Area Electronics
Authors: Fogarassy E. , Prévot B. , Unamuno S. de , Prat C. , Zahorski D. , Helen Y. , Mohammed-Brahim T. 
Published: April 2011

AbstractIn this work, was investigated both numerically and experimentally, the excimer laser processing of a-Si films deposited on SiO2-coated glass substrates, using the very large area (∼ 20 cm2) and long pulse duration (200 ns) excimer source from SOPRA Company. Experiments were carried out in air or in neutral atmosphere, using both the single- and multi-shot mode. From the microstructural analysis of the laser irradiated area the formation of a large-grained material through the so-called SLG regime was evidenced. In addition, the application of a multi-shot process was demonstrated to be very efficient to prepare uniform polysilicon layers with enlarged grain sizes (up to 1.5 µm after 20 shots). Finally, poly-Si TFTs prepared in the optimized conditions (multi-shot, neutral ambience) exibited field effect mobilities up to 235 cm2/V.s (for N-type) and 84 cm2/V.s (for P-type), with fairly uniform device characteristics over large area and excellent stability under electrical stress.
Strain Relaxation Mechanisms in He+-Implanted and Annealed Si1−xGex Layers on Si(001) Substrates
Authors: Christiansen S.H. , Mooney P.M. , Chu J.O. , Grill A. 
Published: April 2011

AbstractStrain relaxation in He+-implanted and annealed Si(001)/Si1−xGex heterostructures was investigated using transmission electron microscopy techniques and x-ray diffraction. Depending on the implant conditions, bubbles and/or platelets form below the Si/Si1−xGex interface upon annealing and act as nucleation sources for dislocation loops. The dislocation loops extend to the interface and form a misfit dislocation network there, resulting in relaxation of 30-80% of the strain in layers as thin as 100-300 nm. When bubbles form close to the interface, dislocations nucleate by a climb loop mechanism. When smaller bubbles form deeper in the Si substrate an irregular three-dimensional dislocation network forms below the interface resulting in an irregular misfit dislocation network at the interface. When platelets form deeper in the Si substrate, prismatic punching of dislocation loops is observed and dislocation reactions of misfit dislocations at the interface result in Lomer dislocation formation.
Si/SiGe Nanostructures Fabricated by Atomic Force Microscopy Oxidation
Authors: Bo Xiang-Zheng , Rokhinson Leonid P. , Yin Haizhou , Tsui D. C. , Sturm J. C. 
Published: April 2011

AbstractIn this work, local AFM oxidation technique in a controlled humidity environment has been used to create small features in strained SiGe alloys. When directly oxidizing SiGe alloys, minimum line widths of 20nm were achieved by adjusting parameters such as the bias voltage on the microscope tip and the tip writing speed. It was found that when bias voltage increases, and/or when the tip writing speed decreases, the oxidation height of silicon-germanium increases. In contrast to conventional thermal oxidation, the oxide height on SiGe alloys is slightly less than that on Si. Finally, this method was used to successfully cut conducting SiGe quantum well lines with high resolution.
Silicon Single-Electron Transistors and Single-Electron CCD
Authors: Takahashi Yasuo , Fujiwara Akira , Ono Yukinori , Inokawa Hiroshi 
Published: April 2011

AbstractWe have developed two types of devices for silicon-single-electronics; a single-electron transistor (SET) and a single-electron charge coupled device (CCD). Both devices were fabricated on SOI (silicon on insulator) wafers. For the SET fabrication, we used a novel method called pattern-dependent oxidation (PADOX), which exploits special phenomena that occur during thermal oxidation of a small silicon structure. The Si structures are converted into small Si SETs by consequence of stress-induced bandgap narrowing and quantum size effects. Since the size of the resultant Si island is about 10 nm, the SETs operate at relatively high temperatures. We have already developed several kinds of application of Si SETs by utilizing the special features of SETs. In addition, we have developed a single-electron CCD that enables us to manipulate a single electron without tunnel capacitors. The device utilizes small Si-wire MOSFETs connected in series, and an elementary charge can be transferred like in a CCD.
Interfacial Diffusion Studies of Hf and Zr into Si from Thermally Annealed Hf and Zr Silicates
Authors: Quevedo-Lopez M. A. , El-Bouanani M. , Gnade B. E. , Colombo L. , Bevan M. , Douglas M. , Visokay M. , Wallace R. M. 
Published: April 2011

AbstractHf and Zr incorporation from thermally annealed high-κ gate dielectric thin films (4-5 nm) candidates HfSixOy and ZrSixOy into Si are presented. The dielectric films were subjected either to rapid thermal annealing (RTA) or standard furnace annealing in an N2 atmosphere. After annealing, the films were removed by chemical etching prior to depth profiling using both time of flight secondary ion mass spectroscopy (ToF-SIMS), and Heavy Ion Rutherford Backscattering Spectrometry (HI-RBS) combined with UV-ozone oxidation/etching cycles. As-deposited and annealed films were studied using monochromatic X-ray Photoelectron Spectroscopy (XPS), and high resolution TEM. A Zr incorporation depth after annealing of up to 20 nm into the Si substrate was observed. Depth profiling shows that, although most of the remnant Zr after annealing/etching is located at or near the surface of the Si substrate, incorporation into the substrate is also present. No significant Hf diffusion into Si was observed for either RTP or furnace-annealed films
Diffusion Characteristics of Cu in TiN Thin Films
Authors: Gupta Abhishek , Wang Hiyan , Kvit Alex V. , Duscher Gerd , Narayan Jay 
Published: April 2011

AbstractWe have investigated the diffusion characteristics of Cu in nanocrystalline, polycrystalline and single crystal TiN thin films, which are being used as a diffusion barrier for sub-quarter-micron metallization. These films were synthesized on Si (100) substrate by first ablating TiN and then ablating Cu targets using Pulse Laser Deposition technique. The three different microstructures of TiN were achieved by growing the films at different substrate temperatures, where higher temperatures (650 °C) leads to epitaxy. Then a uniform thin layer of Cu was deposited on TiN/Si substrate at room temperature for all the three depositions above. These structures were characterized using X-Ray diffraction technique and high-resolution transmission electron microscopy. Each sample is then annealed at 500 °C for 30min to study the diffusion barrier characteristics as a function of microstructure of TiN. Study of diffusion profile and Cu concentration measurement were performed using Scanning Transmission Electron Microscopy-Z contrast Imaging (0.12nm resolution), Electron Energy Loss Spectroscopy and Secondary Ion Mass Spectroscopy. From the results obtained the effect of microstructure of TiN thin films on the diffusion characteristics of Cu after annealing was analyzed. Four points probe resistivity measurements were made to establish structure property correlations.
Strength Analysis of a Micro-Rocket Combustion Chamber
Authors: Noonan Erin E. , Protz Christopher S. , Peles Yoav P. , Mark S. 
Published: April 2011

AbstractThis paper presents the fabrication, testing and analysis of the MIT micro-rocket combustion chamber structure. The structure is a rocket chamber with a closed throat and pressure feeds. It is fabricated with the same processes as the full micro-rocket builds. Mechanical test results are correlated with inspection of failed devices for flaws and with finite element modeling of the test condition. This analysis provides recommendations for modifications to improve the strength of the micro-rocket chamber. These recommendations are discussed in the context of the current status of the micro-rocket.
Frictional Properties of Self-Assembled Alkylsilane Chains on Silica
Authors: Chandross M. , Park B. , Stevens M. , Grest G.S. 
Published: April 2011

AbstractWe present the results of molecular dynamics simulations of pairs of alkylsilane monolayers on silica surfaces under shear. In particular, we investigate the effects of shear velocity on the friction for chains of 6, 8, 12, and 18 carbon atoms covalently bonded to a crystalline surface. Our studies are performed at loads close to 0.2 and 2 GPa for relative velocities of 0.2, 2.0, and 20.0 m/s. We find that for perfect (defect-free) monolayers, the effects of chain length and velocity are weak, indicating that the experimentally measured dependence of friction on these properties is primarily due to defects in the monolayer. We have investigated possible finite size effects by varying our system dimensions from 43 Å ×50 Å Å to 174 Å × 201 Å. We find that increasing the surface area by a factor of N reduces the noise in the shear stress by a factor of , and has a comparable effect to averaging the smaller system data over bins of points. This indicates that finite size effects are negligible in our simulations.
Process Development of Silicon-Silicon Carbide Hybrid Micro-Engine Structures
Authors: Choi Dongwon , Shinavski Robert J. , Steffier Wayne S. , Hoyt Skip , Spearing S.Mark 
Published: April 2011

AbstractA MEMS-based gas turbine engine is being developed for use as a button-sized portable power generator or micro-aircraft propulsion source. Power densities expected for the micro- engine require high combustor exit temperatures (1300-1700K) and very high rotor peripheral speeds (300-600m/s). These harsh operating conditions induce high stress levels in the engine structure, and thus require refractory materials with high strength. Silicon carbide has been chosen as the most promising material for use in the near future due to its high strength and chemical inertness at elevated temperatures. However, techniques for microfabricating single- crystal silicon carbide to the level of high precision needed for the micro-engine are not currently available. To circumvent this limitation and to take advantage of the well-established precise silicon microfabrication technologies, silicon-silicon carbide (SiC) hybrid turbine structures are being developed using chemical vapor deposition of poly-SiC on silicon wafers and wafer bonding processes. Residual stress control of SiC coatings is of critical importance to all the silicon-silicon carbide hybrid structure fabrication steps since a high level of residual stresses causes wafer cracking during the planarization, as well as excessive wafer bow, which is detrimental to the subsequent planarization and bonding processes. The origins of the residual stresses in CVD SiC layers have been studied. SiC layers (as thick as 30µm) with low residual stresses (on the order of several tens of MPa) have been produced by controlling CVD process parameters such as temperature and gas ratio. Wafer-level SiC planarization has been accomplished by mechanical polishing using diamond grit and bonding processes are currently under development using interlayer materials such as silicon dioxide or poly-silicon. These process development efforts will be reviewed in the context of the overall micro-engine development program.
Diffusion Mechanism of Cations and Anions in Cation-Exchange Process for Fabrication of High-Tc Superconducting HgBa2CaCu2O6+δ?Films
Authors: Xie Y. Y. , Wu J. Z. , Aytug T. , Christen D. K. 
Published: April 2011

ABSTRACTWe have investigated the diffusion mechanism of Hg and Tl cations in cation-exchange process that has been used successfully for fabrication of Hg-based high-Tc superconducting films. Scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) was employed to map the distribution of Tl and Hg cations in films quenched at different stages of the cation exchange process. SEM/EDS mappings showed that the nonuniform distribution of Hg is visible in micrometer size on the surface of samples quenched after short-time (∼10min) Hg-annealing, but this nonuniformity disappears for longer-time (∼45 min) Hg-annealing samples. This change could be ascribed to different stages in Hg diffusion -- the former is the early stage when Hg is concentrated in the channels and the latter Hg-cations have already diffuse to grains. Our experimental results hence suggest that Hg-cations channel through defects in the films then diffuse into grains along a-b planes and vise versa for Tl-cations. The diffusion mechanism of anions (oxygen) in post annealing has also been discussed. Fluorine-doped Hg-1212 films were post annealed in flowing oxygen at 300 °C for several hours. Magnetic measurement has shown these samples are comprised pure overdoped Hg-1212 phase with smooth and sharp transition below 120 K, but resistivity vs. temperature measurement shows a kink at ∼123 K. This implies that the optimally doped Hg-1212 phase with higher Tc might be surrounded by overdoped Hg-1212 phase and their contribution to magnetization is minimized, thus the possible diffusion mechanism for anions is also through grain boundaries at a much larger time scale compared to the cations.
Influence of Lateral Critical Current Density Distributions on AC Transport Losses for Ag-Sheathed (Bi, Pb)-2223 Multifilamentary Tapes with Different Filament Arrangements
Authors: Inada Ryoji , Sakamoto Shusaku , Zhang Pingxiang , Oota Akio , Fujimoto Hiroyuki 
Published: April 2011

ABSTRACTThe influence of lateral critical current density (Jc) distributions on AC transport losses in self-fields at 77 K have been investigated on the Ag-sheathed (Bi, Pb)-2223 multifilamentary tapes with different filament arrangements. The trapped magnetic field distributions in a remanent state on the tape surface measured by a scanning Hall sensor depend on the filament arrangements and gradually deviate from the calculation results of magnetic profile without any Jc variations in their cross sections. The transport loss values are strongly influenced from the filament arrangements in each tape, although the main contribution to the losses comes by the hysteresis loss in the superconductor. These results are explained by the calculation results of the shape of field-free core and flux-penetration-regions, varying with filament arrangements and local Jc distributions along a width direction.
Search for New Thermoelectric Materials through Exploratory Solid State Chemistry. The Quaternary Phases A1+xM3−2xBi7+xSe14, A1−xM3−xBi11+xSe20, A1−xM4−xBi11+xSe21 and A1−xM5−xBi11+xSe22 (A = K, Rb, Cs, M = Sn, Pb) and the Homologous Series Am[M6Se8]m[M5+nSe9+n]
Authors: Mrotzek Antje , Hogan Tim , Kanatzidis Mercouri G. 
Published: April 2011

ABSTRACTThe compound types A1+xM3-2xBi7+xSe14, A1−xM3−xBi11+xSe20, A1−xM4−xBi11+xSe21 and A1−xM5−xBi11+xSe22 (A = K, Rb, Cs; M = Sn, Pb) form from reactions involving A2Se, Bi2Se3, M and Se. The single crystal structures reveal that they are all structurally related so that they all belong to the homologous series Am[M6Se8]m[M5+nSe9+n] (M = di- and trivalent metal), whose characteristics are three-dimensional anionic frameworks with tunnels filled with alkali ions. The building units that make up these structures are derived from different sections of the NaCl lattice. In these structures, the Bi and Sn (Pb) atoms are extensively disordered over the metal sites of the chalcogenide network, giving rise to very low thermal conductivity. These phases are all narrow gap semiconductors with 0.25 < Eg< 0.60 eV and many possess physico-chemical and charge transport properties suitable for thermoelectric investigations.
The Hall Carrier Mobility of AgBiTe2-Ag2Te Composite
Authors: Sakakibara T. , Takigawa Y. , Kurosawa K. 
Published: April 2011

ABSTRACTWe prepared a series of (AgBiTe2)1−x(Ag2Te)x(0≤×≤1) composite materials by melt and cool down [1]. The Hall coefficient and the electrical conductivity were measured by the standard van der Pauw technique over the temperature range from 93K to 283K from which the Hall carrier mobility was calculated. Ag2Te had the highest mobility while the mobility of AgBiTe2was the lowest of all samples at 283K. However the mobility of the (AgBiTe2)0.125(Ag2Te)0.875composite material was higher than the motility of Ag2Te below 243K. It seems that a small second phase dispersed in the matrix phase is effective against the increased mobility.
Sb3Zn4, a promising new thermoelectric material. Elaboration and caracterisation
Authors: Izard V. , Record M.C. , Haines J. , Tedenac J.C. 
Published: April 2011

Sb-Zn alloys have interesting thermoelectric properties. Sb3Zn4 is a high performance ptype thermoelectric material appearing as a promising substitute for PbTe due to a higher factor of merit, ZT=1.3 at 673K [1] with the advantage of being Pb free. The preparation of the Sb3Zn4 compound is, however, not without problems. Even if some authors reported measurements on a single-phased material or single crystals [1,2], others described it as multi-phased alloy giving confused explanations for this result based on the existence of metastabilities due to strong interactions in the liquid phase [3,4].Hence, the knowledge of a very trustful phase diagram of the Sb-Zn sytem is indispensable. As the previous published data on this system were discordant, we have reinvestigated it and from our results we have elaborated and characterised the thermoelectric compound Sb3Zn4.
Determining the Limit of Hardness in Ternary Carbide thin Films
Authors: Krzanowski James E. , Endrino Jose L. , Koutzaki Sirma H. 
Published: April 2011

AbstractIn this study we examine the structure and mechanical properties of ternary carbide films, with the objective of understanding the role that residual stress, density, grain size, texture and crystallinity play in determining film hardness. The main variables we used to alter film structure are the nominal film compositions and substrate bias voltage. The systems examined here are Ti-Hf-C and Hf-Si-C, and are compared to previous work on Ti-Si-C. The Hf-Si-C films show hardness levels above that of HfC alone. Residual stress measurements show a compressive stress to be present, with the exception of the -25V sample where the stress was tensile. However, compositional analysis of the biased samples by XPS reveals that Si content in the films is reduced by the application of substrate bias. Consistent with this, the films with higher bias have larger grain sizes and better crystallinity. For the Ti-Hf-C films, the results for hardness vs. bias are consistent with known stress and densification effects of the bias, and values are consistent with rule-of-mixtures expectations.