bluuebunny/crossref_metadata_2025_split huggingface dataset:
Production and Characterization of Circularly Polarized Soft X-Rays for Materials Research at the ALS
Authors: Young Anthony T. , Kortright Jeffrey B. , Hussain Zahid , Martynov Vladimir , Padmore Howard A. , Renner Tim , Smith Neville V. , Warwick Tony 
Published: April 2011

AbstractThe experimental program at the Advanced Light Source to produce and characterize circularly polarized x-rays is described. A number of beamlines are either operating or under construction which produce circularly polarized light. Bend magnets, multilayer phase retarders, and insertion devices which directly produce circularly polarized radiation are described. These beamlines will have capabilities for both microscopy and high resolution spectroscopy. Measurements of the linear and circular polarization of these beamlines are also described.
Silicon L2, 3-Edge Xanes Study of Platinum Silicide Thin Films
Authors: Naftel S. J. , Sham T. K. , Das S. R. , Xu D.-X. 
Published: April 2011

AbstractPlatinum silicide films, with a typical thickness of several hundred Å, prepared on n-type Si(100) wafers by UHV mnagnetron sputter deposition followed by rapid thermal annealing, have been studied by Si L2,3-edge X-ray absorption near edge structure (XANES) using both total electron and total fluorescence yield detection. Samples of various annealing times were studied. XANES provides information on the electronic structure and morphology of the samples. By utilizing the sampling depth difference between the two detection methods, we can clearly see XANES data from each layer (eg. surface oxide, silicide) in the sample and can estimate the thickness of the oxide layer.
Excimer Laser Fabrication of Polycrystalline ZrO2 Layers
Authors: Starbov N. , Mednikarov B. , Mankov V. , Georgiev D. G. , Hanus F. , Kolev K. , Laude L. D. 
Published: April 2011

AbstractPolycrystalline zirconia layers have remarkable low thermal conductivity and thermal expansion coefficient, high melting temperature and mechanical properties which are objects of interest in materials science. In this work thin polycrystalline zirconia films were obtained by two different excimer laser treatment ways. In the first one, pulsed laser deposition (PLD) is used to obtain directly as-deposited polycrystalline layers from a sintered, partially stabilized zirconia target. In the second one, excimer laser irradiation is used to crystallize previously electron gun-deposited amorphous zirconia films. Reflection high energy electron diffraction(RHEED) and low angle X-ray diffraction(LAXRD)-techniques were used to study the structure evolution of both types of films. In both cases, it is shown that cubic polycrystalline films are readily obtained.
Surface Roughening, Columnar Growth and Intrinsic Stress Formation in Amorphous CuTi Films
Authors: Hulsen U. v. , Thiyagarajan P. , Geyer U. 
Published: April 2011

AbstractThe growth of amorphous CuTi films, prepared by electron beam evaporation, is investigated by Scanning Tunneling Microscopy (STM), Small Angle Neutron Scattering (SANS) and in situ measurements of intrinsic mechanical stresses (ISM). In early growth stages the films develop compressive stresses and, with increasing film thickness, a crossover to tensile stresses. In the same thickness range the STM investigations show a change in the growth mode. Our experiments suggest a transition from planar growth with statistical surface roughening to columnar growth.
Nanocharacterization of Texture and Hillock Formation in Thin Al And Al-0.2%Cu Films for Thin-Film Transistors
Authors: Takatsuji H. , Tsuji S. , Kitahara H. , Tsujimoto K. , Kuroda K. , Saka H 
Published: April 2011

AbstractThe relation between the nanostructure of pure Al and Al-0.2 wt.% Cu thin films on glass substrates and anti-stress migration properties were investigated. These films were deposited on liquid-crystal display (LCD) grade glass substrate (550 x 650 mm) by means of two types of dc magnetron multi-chamber sputtering apparatus.We developed the nanoindentation techniques to accelerate the characterization time for stress migration test. By AFM and cross-sectional TEM observations, we found an unusual three-layer structure in a Al-Cu thin film with strong anti-stress migration property.
Substrate Curvature Change Due to Morphological Instability of a Strained Epitaxial Surface Film
Authors: Jonsdottir F. , Freund L. B. 
Published: April 2011

AbstractThe curvature induced in the substrate of a film-substrate system as a result of an epitaxial mismatch strain in a film of nonuniform thickness is considered. In particular, the change in curvature of the substrate due to a transition in film surface morphology from a fiat to a wavy profile is determined numerically. It is found that the amount of curvature relaxation accompanying the instability is within the resolution of recently refined substrate curvature measurement methodologies.
Surface Structure and Morphology Modification of Silicon Layers Induced by Nanosecond Pulsed Laser Irradiation
Authors: Demchuk A. 
Published: April 2011

AbstractThe results of laser induced surface structure modifications utilizing time-resolved reflectivity measurements are presented for the pulsed laser irradiation (λ. = 1.06 μm and 0.53 μm) of thin polysilicon (poly-Si) layers of 0.1 μm, 0.45 μm and 1.0 μm in thickness on silicon substrates. It was shown that when the poly-Si layer of 0.1-0.45 thickness is totally molten, during a solidification, a large-grained structure having grain sizes exceeding the thickness of the molten Si layer is formed. At the same time, the time-resolved reflectivity changes its value nonmonotonically. This nonmonotonic behavior is due to the outcropping of growing grains onto the surface before the formation of a solid crystalline front as well as to the influence of the surface phenomena on the crystallization process.
Determination of Film Growth Rate and Surface Roughness using In-Situ Pyrometry
Authors: Yina Z. , Akkerman Z. L. , Smith W. , Gat R. 
Published: April 2011

AbstractA model for the infrared radiation emitted by a film/substrate system has been developed which includes both the effects of interference in the growing film and of scattering from its rough growth surface. Predictions of the model for the time-dependence of the apparent temperature Tapp of the film/substrate system measured in-situ by both one-color and two-color infrared pyrometers are presented for the case of diamond growth on Si. Using this model, the following information can be obtained from in-situ pyrometric results in real time: the true temperature of the film/substrate system, the instantaneous film growth rate, and the rms surface roughness σ of the film.
Wear Resistant Amorphous PVD B-N-C Films for Tribological Applications
Authors: Knotek O. , Lugscheider E. , Barimani C. , Siry C. W. 
Published: April 2011

AbstractAmorphous B-N-C films with a variety of properties were deposited by PVD-magnetronsputter-ion-plating. Compared to nonconductive reactive r.f. BN-targets the semiconductive behaviour of specially produced B4C-targets permitted a d.c. reactive or non-reactive mode of deposition. These films are characterized by high hardness with decreased coefficient of friction. A tribological evaluation by modified pin-on-disk outline the wear protection effects in tribosystems with metal counter part. This work was partially financed by the Commission of the European Community under Brite/EuRam contract BRE2-CT93-0451.
Effects of the Plasma Conditions on the Bonding Type in Carbon Nitride Thin Films
Authors: Mdndez J M. , Muhl S. , Gaona-Couto A. , Jiménez-Sandoval Sergio 
Published: April 2011

AbstractCarbon nitride thin films have been prepared by plasma enhanced chemical vapour deposition of CH4 and N2 gas mixtures, by chemical transport from a hollow graphite cathode and by reactive sputtering of a high purity graphite target. The vibrational properties of the films have been studied by Fourier transform infrared spectroscopy (FTIR) and Raman microprobe spectroscopy. Optical emission studies from the plasmas were obtained in the range between 275 and 800 nm. Single, double and triple carbon nitrogen bonds were detected in the FTIR spectra by bands at 1230 cm-1, 1600 cm-1 and 2150 cm-1; their relative intensity being a function of the temperature of the species and the energy supplied to the plasma. A correlation was found between the nitrogen concentration in the films and the existance of strong emission lines of CN and N2+. In the sputtered samples, the substrate temperature and the amount of ion bombardment determined when the films were hard; i.e. Vicker's hardness values above 2500 HV. In the case of the sputtered samples, a temperature window was found which resulted in hard films.
Thermodynamic Analysis of Blanket and Selective Epitaxy of Sic on Si and SiO2 Masked Si
Authors: Gao Y. , Edgar J. H. 
Published: April 2011

AbstractThermodynamic analysis was conducted to determine the conditions necessary for the selective epitaxial growth (SEG) of SiC on SiO2 masked Si substrates, and these results were compared to blanket SiC epitaxy on plain Si. For blanket SiC epitaxy, proper deposition conditions leading to single phase SiC without Si or graphite codeposition were found. For SiC SEG, the additional constraint that no significant SiO2 mask etching should occur, was considered. Taken in combination, both the SiC deposition and the Si0 2 etching processes were analyzed to ensure meaningful subsequent experiments. All process parameters, i.e., temperature, C/Si, CI/Si and H2/Si in the gas mixture significantly affect the growth conditions when epitaxy is possible. Either providing more carbon than silicon in the gas sources or adding HCl helps to suppress Si codeposition. For SiC SEG, lower deposition temperature (e.g. less than 1400 K) should be used to avoid damaging the SiO2 mask.
Simultaneous Monitoring of Wafer- and Environment-States During Molecular Beam Epitaxy
Authors: Knopp K. J. , Ketterl J. R. , Christensen D. H. , Pearsall T. P. , Hill J. R. 
Published: April 2011

AbstractWe report the simultaneous monitoring of the environment-state and wafer-state during epitaxial crystal growth using a single real-time measurement. Atomic absorption spectroscopy (AAS) is used to monitor the incident molecular beam flux while UV reflectance (UVR) at 396 nm with an incident angle of 78° is used to monitor growth on the wafer. We have studied the utility of AAS/UVR monitoring of AlxGa1-xAs deposition: AlAs growing on GaAs, GaAs on AlAs, and superlattice growth. Additionally, optical multichannel spectroscopy (OMS) data were acquired throughout the growth of a distributed Bragg reflector (DBR). The relationship of the structure of the real-time OMS data to absorption, optical path length variation, and differential layer thickness variations is also discussed. Numerical simulations of the real-time wafer-state monitors using pseudodielectric constants, appropriate at a growth temperature of 579 °C, show good agreement with measured spectra.
Lateral grain growth in poly-Si films by gas flame high temperature annealing
Authors: Qu W. F. , Kitagawa A. , Masaki Y. , Suzuki M. 
Published: April 2011

AbstractPoly-Si films with the preferential orientation to a random, a (100) and a (110) texture were annealed using a flat gas flame. Remarkable lateral grain growth of (111) grains was observed for poly-Si films with a random and a (110) texture, while in (100) texture films the growth of (100) grains predominated over other grains. There existed tensile stress in as-prepared films. Grains with different orientation were under a different tensile stresses, and such stress distributions on the orientation of grains were different for different textures. The tensile stress was found to become larger in grown grains after high temperature annealing, while the stress on shrunken grains decreased or turned to compressive stress after annealing. These results indicate that strain energy stored in grains is one of the important driving forces in secondary grain growth.
Delamination Trends of Underfill in Dca Assemblies
Authors: Sha Y. , Hui C.Y. , Kramer E. J. , Borgesen P. , Westby G. 
Published: April 2011

AbstractUnderfill delamination is one of the most common failure mechanisms for the Direct Chip Attach (DCA) assemblies. This paper, based on finite element and analytical analysis of stress concentrations, proposes the possible delamination trends of the underfill in the DCA assembly. The results explain well the recent experimental observations. The analysis suggests that good adhesion between underfill and solder joints might help compensate for the relatively poor adhesion of the underfill/passivation interfaces. It also suggests that voids in the underfill material may sometimes be detrimental.
Characterization Of Glass-Ceramic Dielectric Thick Films With Cu Conductors for Multilayer Packages
Authors: Cho Yong S. , Koyuncu Metin , Schulze Walter A. , Amarakoon Vasantha R. W. 
Published: April 2011

AbstractCompatibility and characteristics of multilayer dielectric thick films with Cu interlayers are influenced by composition and processing parameters. In this work, cordierite based dielectric thick films on a Cu plated alumina substrate were investigated in terms of microstructure and property by changing composition of oxide additives, PbO and Cu2O for a given heating schedule. A nonstoichiometric cordierite composition, 2.4MgO 2Al2O3 5SiO2 was used with nucleating agents, B2O3 and P2O5. The dielectric ink consisting of cordierite glass frit and acrylic based binder vehicles was deposited on oxidized Cu layers via screen printing. The thick film layers were fired at 950°C for 30 min in N2 atmosphere. Dissolution of the oxidized Cu into the cordierite layer was observed. The addition of a small amount of Cu2O to the cordierite layer was effective in preventing the dissolution and enhancing thermal expansion. Crystallization was also influenced by the Cu2O addition. A lower activation energy value of 79 kcal/mol for crystallization, calculated from DTA runs, suggested that Cu20 could be used to form the cordierite glass-ceramic at a lower temperature. In the case of no additive, the activation energy for crystallization was 98 kcal/mol. The addition of Cu2O increased dielectric constant. For 3wt% PbO and 1wt% Cu2O, the dielectric constant and loss were determined at 1 MHz as 6.1 and 0.0046, respectively.
Electron-Beam Moiré Study Of Local Deformation In Conductive Adhesives
Authors: Drexler E. S. , Berger J. R. 
Published: April 2011

AbstractElectron-beam (e-beam) moiré is a recently developed technique for micro-mechanics. It allows one to combine the resolution of the scanning electron microscope (SEM) with the strain measurement capabilities of moiré. With e-beam moiré we are able to study locally the effect of temperatures ranging between −50 and 150 °C on conductive adhesives (CAs) and their interfaces. With this technique we measured the local displacements due to the thermal expansion of the copper and the CA. The modified lap-shear specimens were made of copper-to-copper attached with CAs and cured according to the manufacturer's instructions. A cross section of each material was polished and a moiré grating was written on the surface using e-beam lithography techniques. Digital images of the moiré were collected from the SEM at regular temperature intervals. The images were compared and the displacements measured. Local regions of large displacements were observed in the paste specimen. Permanent deformations in the film specimen resulted from exceeding the glass transition temperature of the CA.
Foamed Elastomers For Packaging Interconnections, Testing And Burn‐In Applications
Authors: Liao Y. , Shih D.Y. , Hedrick J.L. , Lauro P.A. , Fogel K.E. 
Published: April 2011

AbstractThe present study is directed to a new foamed elastomer composition for supporting the interconnecting conductive wires in the Elasticon™ interposer connector for the packaging interconnections, test and burn‐in applications. The compressibility of interposer connector can be tailored by introducing controlled volume fraction of foam into elastomer or filled elastomer. The foamed elastomer has been successful applied to a new Ball Grid Array (BGA) module testing socket to meet the contact force requirement.
Tunnel Effects in Luminescence Spectra of InGaN/AlGaN/GaN Light-Emitting Diodes
Authors: Yunovich A. E. , Kovalev A. N. , Kudryashov V. E. , Manyachin F. I. , Turkin A. N. , Zolina K. G. 
Published: April 2011

ABSTRACTTunnel effects in luminescence spectra and electrical properties of blue InGaN/AlGaN/GaN LEDs were studied. The tunnel radiation in a spectral region of 2.1–2.4 eV predominates at low currents (J<0.2 mA). The role of tunnel effects grows as the maximum of the main blue line in LEDs is shifted to short wavelengths. The position of the tunnel maximum ћωmax is approximatly proportional to the voltage eU. The spectral band is described by the theory of tunnel radiative recombination. Current-voltage characteristics have a tunnel component at low direct and reverse currents. The distribution of charged impurities was received from dynamic capacitance measurements. There are charged layers at heterointerfaces and adjacent compensated layers in the structures. There is a high electric field in the active layer. The energy diagram is analysed.
Observation of Near Band Edge Transition in Aluminum Nitride Thin Film Grown by MOCVD
Authors: Tang Xiao , Hossain Fazla R. B. , Wongchotigul Kobchat , Spencer Michael G 
Published: April 2011

ABSTRACTThe Cathodoluminescence (CL) measurements of undoped and carbon doped aluminum nitride (AlN) thin films near the band-edge region were performed at 300, 77 and 4.2 K, respectively. These films were grown on three different substrates: 6H-SiC, 4H-SiC and sapphire. A dominant peak was observed in undoped samples around 5.9 eV. This peak can be further resolved into three distinct peaks at 6.05, 5.85, and 5.69 eV for AlN on sapphire. The temperature dependence of the peak positions and line widths were investigated. These peaks are believed to be due to exciton recombination. Also, the absorption spectra of carbon doped AlN on sapphire were analyzed to study the Urbach tail parameters which play an important role in near band-edge transitions.
Visible Blind uv GaN Photovoltaic Detector Arrays Grown by rf Atomic Nitrogen Plasma MBE
Authors: Van Hove J.M. , Chow P.P. , Hickman R. , Wowchak A.M. , Klaassen J.J. , Polley C.J. 
Published: April 2011

ABSTRACTRF atomic nitrogen plasma molecular beam epitaxy (MBE) was used to deposit gallium nitride (GaN) p-i-n junction photovoltaic detectors on (0001) sapphire. The detectors consisted of a bottom contact layer n-type silicon doped to 5 × 1018 cm−3. The intrinsic layer was undoped and possessed an n-type background carrier concentration of 1 × 1016 cm−3. The top /p-GaN layer was doped with magnesium to give a Hall concentration of 5 × 1017 cm−3. The p-type GaN cathodoluminescence (CL) spectra showed a strong 372 nm emission level in contrast to the 430 nm level observed in MOCVD samples. These layers were fabricated into 1 × 10 element detector arrays using a chlorine-based reactive ion etch (RIE) and refractory metal ohmic contacts. Peak responsivity of 0.11 AAV on detectors without anti-reflection coating were obtained at the GaN bandedge of 360 nm. The ultraviolet (UV) to visible rejection ratio was greater than 103 − 104 and was accredited to the reduction of the yellow defect levels in MBE material. Preliminary results on AlxGa1−xN detectors with responsivity peaks at 313 and 343 nm are presented as well.
GaN Quantum Dots in AlxGa1-xN Confined Layer Structures
Authors: Tanaka Satoru , Hirayama Hideki , Iwai Sohachi , Aoyagi Yoshinobu 
Published: April 2011

ABSTRACTNanoscale GaN quantum dots were fabricated in AlxGa1-xN confined layer structures via metalorganic chemical vapor deposition (MOCVD), by using a ‘surfactant’ which can modify the GaN growth mode on AlGaN surfaces. A two dimensional growth mode (step-flow-like) of GaN films on AlxGa1-xN (x=0∼0.2) surfaces, that is energetically commenced under the conventional growth conditions, was intentionally changed into a three dimensional mode by adding tetraethyl-silane (TESi) used as a surfactant onto the AlGaN substrate surface prior to the GaN deposition. The surfactant is believed to inhibit the GaN film from wetting the AlGaN surface due to the change in surface free energy. The resulting morphological structures of GaN dots were found to be sensitive to; the doping rate of TESi, the Al content (x) of the AlxGa1-xN layer, and the growth temperature. A very intense photoluminescence (PL) emission was observed from the GaN dots embedded in the AlGaN layers. The quantum size effect in terms of the blue-shift in a PL peak position was verified using the GaN dot samples having different dot sizes.
Growth of AlBN Solid Solution by OMVPE
Authors: Shin M. , Polyakov A. Y. , Qian W. , Skowronski M. , Greve D. W. , Wilson R. G. 
Published: April 2011

ABSTRACTLayers of AIBN were grown on sapphire by organometallic vapor phase epitaxy (OMVPE) at 1050°C using triethylboron (TEB), trimethylaluminum (TMA) and ammonia as precursors. Boron is readily incorporated into the layers and its concentration in the solid phase can be made fairly high, up to at least 40%. However, single phase AIxB1–xN films can only be grown for compositions not exceeding x=0.01. For higher B concentrations a second B-rich phase is formed. This phase is shown to be most probably wurtzite BN based on the results of transmission electron microscopy and x-ray diffraction. The growth of this phase occurs within the framework of wurtzite AIN islands providing the sites for lateral growth of wurtzite BN. This leads to formation of columnar structure of AIN and BN crystallites oriented in the basal plane and existing side by side. This is one of the first observation of purely thermal growth of sp3 bonded BN.
Growth of Cubic GaN by MBE and Its Properties
Authors: Yoshida S. , Okumura H. , Feuillet G. , Hacke P. , Balakrishnan K. 
Published: April 2011

ABSTRACTMolecular beam epitaxy (MBE) technique is a useful method to grow III-V nitrides, especially those having a metastable crystal structure, like cubic GaN (c-GaN), because of the capability of in situ observation of growing surfaces and its non-equilibrium growth mechanism. We have grown c-GaN on GaAs and 3C-SiC substrates by gas source MBE using dimethylhydrazine or activated nitrogen beam as an N source, and measured their luminescent and optical properties. This paper summarizes the MBE growth and properties of c-GaN, comparing with those of hexagonal one, and the control of the crystal structures is discussed in terms of growth method, orientation of substrate surfaces and growth conditions.
A Study of Mixed Group-V Nitrides Grown by Gas-Source Molecular Beam Epitaxy Using a Nitrogen Radical Beam Source
Authors: BI W. G. , Tu C. W. , Mathes D. , Hull R. 
Published: April 2011

ABSTRACTWe report a study of N incorporation in GaAs and InP by gas-source molecular beam epitaxy using a N radical beam source. For GaNAs grown at high temperatures, phase separation was observed, as evidenced from the formation of cubic GaN aside from GaNAs. By lowering the growth temperature, however, GaNAs alloys with N as high as 14.8% have been obtained without showing any phase separation. For InNP, no phase separation was observed in the temperature range studied (310 – 420 °C). Contrary to GaNAs, incorporating N in InP is very difficult, with only less than 1% N being achieved. Optical absorption measurement reveals strong red shift of bandgap energy with direct-bandgap absorption. However, no semimetallic region seems to exist for GaNAs and a composition-dependent bowing parameter has been observed.