bluuebunny/crossref_metadata_2025_split huggingface dataset:
High-pressure investigation of InGan quantum wells.
Authors: Perlin Piotr , Iota Valentin , Weinstein Bernie A. , Teisseyre Henryk , Suski Tadeusz , Hersee Steeve , Kisielowskil Christian , Weber Eicke R. , Yang Jinwei 
Published: April 2011

ABSTRACTWe have studied the pressure dependence of photoluminescence for various InGaN quantum wells of different Indium compositions. In contrast to classical quantum well systems such as GaAs/AlGaAs, the pressure coefficients of the photoluminescence peak position of wells of similar parameters can vary greatly, depending on conditions of growth. Generally, the pressure coefficient of the emission peak is much lower than the one predicted for a GaN-InN system. We show that this behavior can be related in most cases to the influence of the thick GaN layer compressibility on the strain in the InGaN quantum wells. However, in some cases (Nichia devices), the pressure coefficient of the emission peak seems to be unrelated to the shift of the energy gap of the material, suggesting the involvement of strongly localized electronic states
A New Approach to Growth of Bulk Zno Crystals for Wide Bandgap Applications
Authors: Agarwal G. , Nause J. E. , Hill D. N. 
Published: April 2011

ABSTRACTA novel technique was used to melt zinc oxide powder. This techniques involves the pressurized RF induction heating of ZnO, contained in a water-cooled crucible. The ability to obtain a pool of molten ZnO enables the pulling of large diameter ZnO crystals using conventional melt growth processes. Centimeter-sized crystals were obtained in the preliminary experiments by cooling the ZnO melt. These crystals were analyzed for crystalline perfection and stoichiometry using x-ray diffiraction and photoluminescence. The semiconductor properties of these crystals were also measured. This technology can potentially provide large, low cost ZnO single crystal wafers for use in the fabrication of GaN blue diodes and blue lasers, high temperature / high power FETs, as well as homoepitaxy of ZnO wide band-gap devices. Single crystal zinc oxide also has potential application in the piezoelectric device market.
Optical Anisotropy Studies of Sapphire by Raman Scattering and Spectroscopic Transmission Ellipsometry
Authors: Yao H. , Yan C. H. , Denbaars S. P. , Zavada J. M. 
Published: April 2011

ABSTRACTOptical anisotropy of sapphire have been studied by both polarized Raman scattering and transmission variable angle spectroscopic ellipsometry (TVASE). The polarized Raman effect was measured on both c-plane (0001) and a-plane (2110) sapphire substrates. Two TO phonons (379 and 431 cm−l) and four LO phonons (418, 450, 577, and 750 cm−1) were observed when the optical axis <c> is perpendicular to the polarization of the incident laser beam (for both c-plane and a-plane). While only two TO phonons (379 and 431cm−1) and two LO phonons (418 and 645 cm−1) can be seen when the optical axis is parallel to the polarization for an a-plane sapphire. The optical axis of the a-plane sapphire can then be quickly determined by either maximizing or minimizing the 645 LO peak intensity with about ±10° error. TVASE measurements were carried out in the energy range of 0.75eV to 5.8eV at room temperature. Sizable off-diagonal Jones matrix elements Apst, and Aspt can be detected even with the optical axis 1° off the X-axis. This indicates that TVASE has a high sensitivity to optical anisotropy. By minimizing these off-diagonal elements and combining the Raman analysis, the optical axis orientation of an a-plane or m-plane (0110) sapphire can therefore be fully determined with an error of less than 1°.
Interaction of Nitrogen With 6H-SiC Surfaces
Authors: Elsbergen V. Van , Rohleder M. , Mönch W. 
Published: April 2011

ABSTRACTThe interaction of nitrogen with 6H-SiC surfaces with different orientation and composition ranging from Si-rich to graphitized was investigated by use of X-ray and ultraviolet photoemission spectroscopy (XPS, UPS). The samples were cleaned and their surface composition was tuned by heating them in a Si flux at different temperatures or by annealing. Nitrogen exposures were performed using a RF plasma source operated at 13.56 MHz. Two different nitridation mechanisms can be distinguished by XPS. While anion exchange occurs at bulk-truncated SiC surfaces diffusion will control the nitrogen uptake of Si-rich samples. After nitridation, UPS spectra of bulk–truncated surfaces display characteristic valence-band structures of Si3N4. The thickness of the nitride layer amounts to approximately 9–12 Å. Thicker silicon nitride films on SiC are obtained by rising the sample temperature during nitrogen exposures or by deposition and subsequent nitridation of thin Si overlayers on SiC surfaces. The nitrogen uptake of graphitized samples is comparable to that of bulk-truncated surfaces. Our photoemission spectroscopy results prove that surface graphite is partly removed by N and the UPS spectra point to the formation of silicon nitride. In addition, C-N bonds exist but the exact bonding configuration cannot be resolved.
Ultra-High Implant Activation Efficiency In GaN Using Novel High Temperature RTP System
Authors: Cao X. A. , Abernathy C. R. , Singh R. K. , Pearton S. J. , Fu M. , Sarvepalli V. , Sekhar J. A. , Zolper J. C. , Rieger D. J. , Han J. , Drummond T. J. , Shul R. J. , Wilson R. G. 
Published: April 2011

ABSTRACTSi+ implant activation efficiencies above 90%, even at doses of 5×1015 cm−2, have been achieved in GaN by RTP at 1400–1500°C for 10 secs. The annealing system utilizes with MoSi2 heating elements capable of operation up to 1900 °C, producing high heating and cooling rates (up to 100 °C · s−1). Unencapsulated GaN show severe surface pitting at 1300 °C, and complete loss of the film by evaporation at 1400 °C. Dissociation of nitrogen from the surface is found to occur with an approximate activation energy of 3.8 eV for GaN (compared to 4.4 eV for AIN and 3.4 eV for InN). Encapsulation with either rf-magnetron reactively sputtered or MOMBE-grown AIN thin films provide protection against GaN surface degradation up to 1400 °C, where peak electron concentrations of ∼5×1020 cm-3 can be achieved in Si-implanted GaN. SIMS profiling showed little measurable redistribution of Si, suggesting Dsi ≤ 10-13 cm2 · s−1 at 1400 °C. The implant activation efficiency decreases at higher temperatures, which may result from SiGa to SiN site switching and resultant self-compensation.
High Voltage Silicon Carbide Devices
Authors: Baliga B. Jayant 
Published: April 2011

ABSTRACTProgress made in the development of high performance power rectifiers and switches from silicon carbide are reviewed with emphasis on approaching the 100-fold reduction in the specific on-resistance of the drift region when compared with silicon devices with the same breakdown voltage. The highlights are: (a) Recently completed measurements of impact ionization coefficients in SiC indicate an even higher Baliga's figure of merit than projected earlier. (b) The commonly reported negative temperature co-efficient for breakdown voltage in SiC devices has been shown to arise at defects, allaying concerns that this may be intrinsic to the material. (c) Based upon fundamental considerations, it has been found that Schottky rectifiers offer superior on-state voltage drop than P-i-N rectifiers for reverse blocking voltages below 3000 volts. (d) Nearly ideal breakdown voltage has been experimentally obtained for Schottky diodes using an argon implanted edge termination. (e) Planar ion-implanted junctions have been successfully fabricated using oxide as a mask with high breakdown voltage and low leakage currents by using a filed plate edge termination. (f) High inversion layer mobility has been experimentally demonstrated on both 6H and 4H-SiC by using a deposited oxide layer as gate dielectric. (g) A novel, high-voltage, normally-off, accumulation-channel, MOSFET has been proposed and demonstrated with 50x lower specific on-resistance than silicon devices in spite of using logic-level gate drive voltages. These results indicate that SiC based power devices could become commercially viable in the 21st century if cost barriers can be overcome.
A New Development Of Scanning Hydrogen Imaging System And Its Application
Authors: Ueda Kazuyuki , Ishikawa Ken'ichi , Yoshimura Masamichi 
Published: April 2011

ABSTRACTScanning type electron-stimulated desorption (ESD) spectroscopy to detect hydrogen on solid surfaces has been described. To analyze a two-dimensional distribution of hydrogen on solid surface, a pencil-type fine-focused electron gun, of which spot size is less than 300 nm at 800 eV, has been developed using a thermal field emitter. The lateral resolution of analysis is achieved less than 1 μm.Letters were drawn on a hydrogen-terminated Si(100) surface by irradiation of continuous electron beam to remove hydrogen from the surface, and by the following scanning ESD measurement, a clear letters were confirmed on this surface. Direct lithography by an electron beam on silicon surfaces has been realized.
Neutron scattering studies of the structures and Vibrational Dynamics of the HCP Rare-Earth Trihydrides
Authors: Udovic T. J. , Huang Q. , Rush J. J. 
Published: April 2011

ABSTRACTBoth neutron-powder-diffraction and neutron-vibrational-spectroscopy studies have been undertaken to characterize the structures and vibrational dynamics of a variety of bulk hcp rareearth trihydrides RH3 (where R = Y, Th, Dy, Ho, Er, and Lu). The results are consistent with P3c1 as the prevalent structural symmetry for all trihydrides investigated except LuH3. Corresponding results for LuH3 are suggestive of an atypical arrangement of H atoms. Preliminary analyses of LuD3 diffraction patterns indicate that the main peaks can be satisfactorily modeled using P63/mmc symmetry with a reduced unit cell, although numerous minor diffraction features and a relatively unusual vibrational spectrum hint at either a more complex structure or an unknown secondary phase. The deviations from P3c1 symmetry are likely a consequence of the relatively smaller metal-hydrogen bond distances for LuH3.
The Influence of Nitrogen Implantation on the Hydrogen Distribution in Titanium Observed by Nra and Xps
Authors: Soltani-Farshi M. , Baumanna H. , Baretzky B. , Rück D. , Bethgea K. 
Published: April 2011

ABSTRACTTitanium has a strong chemical affinity and can absorb and store large amounts of hydrogen, which causes embrittlement of the material. Ion implantation is applied to improve wear behavior e.g. of titanium alloys, which are used for load bearing components of hip and knee joint prostheses. Nitrogen implantation influences the hydrogen content in the near surface region of a commercially available pure titanium. 150 keV 15N-ions were implanted at RT into titanium samples with a fluence of 6 × 1017 ions/cm2 and subsequently annealed at 500°C under high vacuum conditions. For comparison N was also implanted at a sample temperature of 500°C. Concentration depth profiles of implanted nitrogen and accumulated hydrogen were measured with Nuclear Reaction Analysis (NRA) and compared to nitrogen and titanium depth profiles obtained with X-ray Photoelectron Spectroscopy (XPS). The results indicate a relation between hydrogen concentration and the formation of Ti-N bonds.
Is an Arsenic-Antisite-Defect a Constituent of Hydrogen-Related:Metastable Defects (M3/M4) In GaAs?
Authors: Okumura T. , Shinagawa T. 
Published: April 2011

ABSTRACTThe hydrogen-related metastable defects (M31M4) in n-GaAs, first found by Buchwald et al., were introduced only in the crystals containing the EL2 center. Off-center oxygen (=EL3), could not be responsible for their formation. A quantitative analysis with the samples exposed to atomic hydrogen showed that the M4 defect consisted of two different configurations. One of them did couple with M3, but is latent in the as-exposed state. It was formed after bias annealing at higher temperatures, such as 420 K. The other part of the M4 defect (M4•) existed at room temperature and after annealing at 513K, but disappeared and reappeared upon forward- and reverse-bias annealings, respectively.
Hydrogen Incorporation into CU-III-VI2 Chalcopyrite Semiconductors
Authors: Otte K. , Lippold G. , Grambole D. , Herrmann F. , Schlemm H. , Schindler A. , Bigl F. 
Published: April 2011

ABSTRACTWe implanted at 300 eV into Cu-chalcopyrite semiconductors at temperatures between 50°C and 300°C. The surface chemistry is similar to the previously reported behavior of CuInS2 implanted with a H2+, H+ low energy ion beam [1] with respect to secondary phase etching. We also found an increase of radiative recombination (photoluminescence), which had been attributed to defect passivation and, hence, as an indicator of hydrogen incorporation [2]. Under the 300 eV implantation conditions, however, we observed neither a hydrogen concentration in a few hundred nm surface range exceeding the NRA detection limit of about 1×1019 cm-3 nor a pronounced stoichiometry variation in the ternary material, as proved by Raman measurements.We conclude, therefore, that a 300 eV implantation introduces significantly less atomic hydrogen into the volume of the sample than previously reported for other beam compositions under similar temperature and current density conditions. This could be a result of the very low energy of less than 100 eV which can be expected for atomic H produced by dissociation of 300 eV at the surface, making the instant out-diffusion into the high vacuum of the implantation chamber a favored process.
Nmr Study in Sodium-Hydrogen-C60 Superconductor
Authors: Ogata H. , Miyajima S. , Imaeda K. , Inokuchi H. 
Published: April 2011

ABSTRACT23Na and 1H NMR studies have been carried out for a NaxHyC60 superconductor The peak position of the 23Na NMR spectrum exhibits discontinuous upfield shift of 30 ppm at about 250 K, indicates a first order phase transition From the line shape of the 23Na spectrum obtained at 7 K, the quadrupole coupling constant tensor is evaluated to be |e2Qq/h|=3.7 MHz with the asymmetry parameter η = 0.95. The 1H NMR spectrum suggests an anionic hydrogen state with weakly delocalized nature.
EPR Study of the Role of Hydrogen in the Defect Formation Upon Heat Treatment of Oxidized SiC
Authors: Macfarlane P. J. , Zvanut M. E. 
Published: April 2011

ABSTRACTFor the past several years hydrogen incorporation in metal oxide semiconductor (MOS) devices has been of interest because studies have shown that vacuum annealing of oxidized Si substrates desorbs hydrogen, revealing interfacial defects. Today, in applications that require higher power and/or temperature, Si will likely be replaced with a wide-band-gap semiconductor. For MOS devices, SiC is a leading contender because it can be thermally oxidized to form a SiO2 insulating layer similar to Si. However, the SiC/SiO2 structure potentially contains hydrogen sensitive centers similar to those found in Si/SiO2 structures. Using electron paramagnetic resonance (EPR), we have observed a center 1.8 G wide peak-to-peak at g=2.0026. The center is generated in oxidized SiC that has received a 900° C dry, N2 or O2, post oxidation heat-treatment in which moisture is measured to be less than 1 ppm. Annealing at 900° C in standard Ar containing at least 50 ppm H2O decreases the center's concentration by two orders of magnitude. By comparing results from our study to studies of Si-H and C-H bonds in a-SiC:H [1] and SiC converted graphite [2], we suggest that this center is related to carbon dangling bonds created by the effusion of hydrogen during the dry heat-treatment. We will compare the activation energy for the hydrogen depassivation of our center with that found for other C-H and Si-H systems.
Effect of Substitutions at the Nickel Site on the Electronic Structure of LaNi5 and its Hydrides
Authors: Gupta M. 
Published: April 2011

ABSTRACTThe effect of Ni substitution in LaNi5 by 3d and s-p elements on the electronic structure of the intermetallic and its hydrides has been investigated using the self consistent linear muffin tin orbital (LMTO) method in the atomic sphere approximation (ASA). The Fermi level, EF, of LaNi4M (M = Fe,Co,Mn) is found to lie in the narrow additional M 3d subband above the Ni d states, leading to an increase in the density of states (DOS) at EF. In contrast, the substitution of Ni by an s element of the 3d series, Cu, or by an s-p element: Al or Sn results in a progressive filling of the Ni-d bands and in a decrease of the DOS at EF. In all the substituted intermetallic compounds, we find that the lattice expansion accounts for less than 50% of the observed decreased stability, this shows the importance of the effect of chemical substitution. We also discuss the factors which affect the electronic structure and the stability of the hydrides and compare our results with available experimental data.
Properties of Mg2NiH4 at 450-570 K
Authors: Guthrie S. E. , Thomas G. J. , Noreus D. , Ronnebro E. 
Published: April 2011

ABSTRACTIt has been established that Mg2NiH4 undergoes a phase change around 500°K in which the orientation of the NiH4 complex is quenched in a monoclinic distortion of the cubic high temperature phase. This results in the formation of domains in which the lattice distortion is accommodated by microtwinning. These effects can be absent when the hydride phase is formed below the transition temperature. Microscopic analysis verifies a similar basal cubic structure in the low temperature phase; however, the domains and microtwins are absent in this material and it can readily be destabilized by thermal stresses induced by the electron beam. It is of interest to measure and compare the effect of the lattice differences on the thermodynamic properties of the low temperature versus the high temperature hydride phases. We report the equilibrium PCT data and hydrogen desorption kinetics of the two hydrides in the temperature range of 450–570 K.
Comparison of the Electromigration Behavior of Al(MgCu) with Al(Cu) and Al(SiCu)
Authors: Li Hua , Witvrouw Ann , Jin Sing , Bender Hugo , Maex Karen , Froyen Ludo 
Published: April 2011

ABSTRACTMg is one of the elements that are regarded as having a beneficial effect on the Al electromigration (EM) lifetime. In this paper, we compare the EM behavior of 0.4 μm wide passivated Al-1%Mg-0.5%Cu, Al-0.5%Cu and Al-l%Si-0.5%Cu lines. Plan-view transmission electron microscopy and focused ion beam imaging reveal that Al(MgCu) film undergoes bimodal grain growth. Auger electron spectroscopy and secondary ion mass spectrometry show a strong surface segregation and a severe bulk depletion of Mg. Additionally the line-width dependence of the rate of the resistivity decay during aging shows also a different behavior for Al(MgCu) compared to Al(Cu) and Al(SiCu). All these findings are consistent with the EM results that Al(MgCu), processed with our experimental conditions, has both the lowest median time to failure and deviation in time to failure. The results are discussed in the light of the effect of Mg addition on the microstructure and of the great surface activity of Mg.
Growth, Patterning and Microelectronic Applications of Epitaxial Cobaltdisilicide
Authors: Mantl S. , Kappius L. , Antons A. , Löken M. , Klinkhammer F. , Dolle M. , Zhao Q. T. , Mesters S. , Buchal C H. , Bay H. L. , Kabius B. , Trinkaus H. , Heinig K. H. 
Published: April 2011

ABSTRACTWe report on the epitaxial growth of CoSi2 on silicon using ion beam synthesis and molecular beam allotaxy. The latter process uses molecular beam epitaxy to grow a silicide precipitate distribution embedded in single crystalline silicon and thermal annealing to form the epitaxial layer. Both, ion beam synthesis and molecular beam allotaxy, are capable to grow epitaxial buried and surface CoSi2 layers on Si(100) and Si(111) of high quality.
Low Temperature Formation of C54 TiSi2 Bypassing the C49 Phase: Effect of Si Crystallinity, Metallic Impurities and Applications TO 0.10 μm CMOS
Authors: Kittl J. A. , Gribelyuk M. A , Samavedam S. B. , Hong Q. Z. , Yu N. , Rodder M. 
Published: April 2011

ABSTRACTThe mechanism and evolution from the early stages of the Ti/Si reaction by rapid thermal processing (RTP) at 650°C in the presence of Mo doping was studied and compared to the case without Mo doping; for amorphous, polycrystalline and single crystal (100) Si substrates. It was found that for Mo doped polycrystalline Si or Mo doped amorphous Si, the low resitivity C54 TiSi2 phase nucleates at the Ti/Si interface and grows following diffusion limited kinetics, bypassing the nucleation of the high resistivity C49 TiSi2 phase. The conventional phase sequence, with C49 TiSi 2 nucleation and growth, was observed on Mo doped (100) Si and all samples without Mo. The mechanism of early C54 nucleation was identified by high resolution transmission electron microscopy (HRTEM): at early stages of the reaction, precursor silicide phases lattice matched to C54 TiSi2 nucleate at the Ti/Mo doped Si interface, and act as templates for epitaxial nucleation of C54 TiSi2. Two such phases were observed, MoSi2 and a phase with spacings of 2.26 Å and 4.2 Å. Image simulations suggest that the structure of the second template phase is based on Mo5Si3. Similar kinetics were observed on large structures and narrow lines for Mo doped Si (except for the case of (100) Si), indicating that this growth mechanism eliminates the linewidth dependence. Implementation on a 0.10 μm CMOS technology of a process combining Mo doping with pre-amorphization (PAI) achieves low source/drain (S/D) sheet resistance, and the first Ti salicide process with low gate sheet resistance down to 0.06 μm.
Mechanism of Narrow Line Effect in TiSi2 films on highly As-Doped Diffusion Layers
Authors: Ishida Koichi , Wakabayashi Hitoshi , Mogami Tohru 
Published: April 2011

ABSTRACTThe mechanism of the narrow line effect in TiSi2, films on highly As-doped diffusion layers is studied by TEM observation of grains in the TiSi2. The narrow line effect is shown to be due to an enlargement of the TiSi2, grain size caused by regrowth of the pre-amorphized regions before the start of silicidation. Knocked-on oxygen from the SiO2 cover layers is found to delay the onset of the silicidation.
The Control and Impact of Processing Ambient During RTP
Authors: Maex Karen , Kondoh Eiichi , Lauwers Anne , DePotter Muriel , Prost Joris 
Published: April 2011

ABSTRACTThe introduction of rapid thermal processing for silicide formation has triggered a lot of research to temperature uniformity and reproducibility in RTP systems. From the other side there has been the demand to make the process itself as robust as possible for temperature variations. Indeed the way the module is set up can open or close the thermal process window for silicidation. In addition to the temperature, the ambient control is to be taken into account. Although gasses are specified to a low level of contaminants, the RTP step needs to be optimized for optimal contaminant reduction. Besides, the process wafer itself can be a source of contamination. In this paper an overview will be given of the role of temperature and ambient during RTP on the silicidation processes. The effect of the wafer on ambient purity will be highlighted. It will be shown that the latter can also have an impact on other process steps in the interconnect technology.