bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Interaction of Laser Generated Methyl Radicals with Cd, Te, and CdTe Surfaces
Authors: Zinck J.J. , Olson G.L. , Brewer P.D. , Jensen J.E. 
Published: March 2011

ABSTRACTThe mechanism of the interaction of methyl radicals with Cd, Te, and CdTe surfaces has been studied in ultrahigh vacuum by Auger electron spectroscopy and thermal desorption mass spectrometry. Methyl radicals generated by the laser photodissociation of acetone at 193 nm efficiently etch both Te and Te-rich CdTe surfaces. However, there is no evidencefor reaction of methyl radicals with Cd or stoichiometric CdTe. A temperature dependencein the rate of methyl radical etching of Te-rich CdTe is related to a competition between acetone scavanging of radicals on the surface and reaction of radicals to form volatile metalorganics. Acetone itself has a small but finite reaction probability with Te and Te-rich CdTe surfaces.
Holographic Pattern Etching of Silicon—Carbide by Excimer Laser
Authors: Murahara M. , Yonekawa M. , Shirakawa K. 
Published: March 2011

ABSTRACTThe diffraction grating on SiC mirror was performed by a laser holographic method. In the present method, KrF laser and CIF3 was used for etchant gas. The ClF3 gas has an absorption band in the range between 200 and 400 nm. Therefore, CIF3 gas is effectively decomposed by the XeF, KrF and ArF excimer lasers' radiation. It is found that absorption of Si—C is about 50% in the range of between200 and 400 nm, and that the bonding energy of Si—C is lower than the photon energy of KrF laser beam. The above results indicate the direct decomposition of Si—Cbond. On the other hand, the threshold fluence energy for etching was 800 mJ/cm2 in 249 nm and in 193 nm as high as 7 J/cm2. In these results, the KrF laser is more effective than ArF laser. Then we applied KrF laser to crystalline SiC in an atmosphere of C1F3 gas. The divided two polarized KrF laser beams were interfered on the substrate. And the beams were used to photodissociated CIF3 gas in the proximity of substrate. Fluence of KrF laser beam was 1 J/cm2. The incidential angle of KrF laser beams was 20º and the grating gaps were 7170 Å, etching depth 1000 Å, and etching rate was 5 Å/pulse.
Novel Stacked CMOS Process by Local Overgrowth
Authors: Zingg René P. , Hüfflinger B. , Neudeck G. W. 
Published: March 2011

ABSTRACTA six mask process that yields stacked CMOS circuits is presented. Transistors that were built in reverse order (i. e. the gate first, the gate dielectric second, and only then the channel region) exhibit comparable parameters as conventional devices. A novel device has been built whose current drive is three times that of FETs built in substrate material. The vertical stacking of complementary MOS transistors made it possible to build an inverter with symmetric switching characteristic within the area of a single transistor.
Laser Induced Surface Chemical Epitaxy of II-VI Materials
Authors: Stinespring Charter D. , Freedman Andrew 
Published: March 2011

ABSTRACTStudies of the thermal and photon-induced surface chemistry of dimethyl cadmium (DMCd) and dimethyl tellurium (DMTe) on GaAs(100) substrates under ultrahigh vacuum conditions have been performed for substrate temperatures in the range of 123 K to 473 K. Results indicate that extremely efficient conversion of admixtures of DMTe and DMCd to CdTe can be obtained using low power (5 - 10 mJ cm−2) 193 nm laser pulses at substrate temperatures of 123 K. Subsequent annealing at 473 K produces an epitaxial film.
Xps Studies of Chlorine Etching Interactions with GaAs(100)
Authors: Freedman Andrew , Stinespring C.D. 
Published: March 2011

ABSTRACTGaAs (100) substrates have been chlorinated with both atomic and molecular beams of chlorine under ultra high vacuum conditions. X-ray photoelectron spectra of the resulting samples indicate that at a substrate temperatures of 130 K, Cl atoms efficiently penetrate the GaAs lattice forming Ga and As chloride species. Exposure to Cl atoms at 173 K results in desorption of As, leaving GaClx species behind. Molecular chlorine reacts much less efficiently.
Direct Evidence for the Creation of Micropores in UV-Irradiated Poly(Methyl Methacrylate)
Authors: Moore J. A. , Choi Jin-O 
Published: March 2011

ABSTRACTFilms of PMMA containing azobenzene were prepared by casting from polymer solutions containing the probe or by exposing pre-irradiated films to the vapor of azobenzene. These materials were irradiated at 335 nm and the amount of trans azobenzene which had been photoisomerized was monitored spectrophotometrically. The largest amount of photoisomerization was observed for the pre-irradiated samples which had been penetrated by azobenzene from the vapor, indicating that the created free volume allowed the isomerization to proceed more easily.
Etching of GaAs on AlGaAs in Rie-Mode
Authors: Kaufel Gudrun , Olander Elfriede 
Published: March 2011

ABSTRACTUsing MBE and MOCVD, High Electron Mobility Transistor (HEMT) structures were grown on two-inch GaAs wafers. The vertical structure included three GaAs layers and two thin (3nm) Al0.3Ga0.7 As etch stop layers to control precisely the depth of the etched recess and hence the threshold voltage of the devices.The structure below the second etch stop layer depends on the particular device to be fabricated, but is irrelevant for the etching process. The selective reactive ion etching of GaAs on AlGaAs is done by a Leybold MPE 3003 Plasma Etcher. The etch gas used is CF2Cl2 for GaAs and Ar for AlGaAs. The pressure lies between 30 µbar and 100 µbar and the self bias voltage between 47 V and 250 V. The standard deviation for enhancement FETs is 12 mV for Vt = +0.13 V and for depletion FETs 18 mV for Vt = -0.48 V.
Uv Laser-Induced Etching of the First-Row Transition Metals
Authors: Tyndall George W. 
Published: March 2011

ABSTRACTThe 248 nm excimer laser-induced etching of Ti, Cr, Fe, Co, Ni, and Cu by Br2 has been studied. The experiment consists of focusing the pulsed UV laser beam at normal incidence onto the surface of a quartz crystal microbalance (QCM) coated with 1μm of polycrystalline metal. Absolute etch rates are determined as a function of the Br2 pressure and the laser fluence. On the basis of the kinetic information, four mechanisms are proposed to explain the etching of these transition metals.
Photochemical Area-Selective Etching of Si And Sio2 Using Synchrotron Radiation
Authors: Takahashi Jun-Ichi , Utsumi Yuichi , Urisu Tsuneo 
Published: March 2011

ABSTRACTPhotochemical etching of Si and SiO2 using synchrotron radiation (SR) is carried out. The etching rate of SiO2 is much higher than those of poly-Si and single crystal Si. The etching rate of poly-Si increases as dopant concentration decreases. These material selectivities are quite different from those for plasma- or laser-excited etching. These new phenomena in SR-stimulated etching can be explained by a reaction model that contains reaction centers that are produced by both core and binding electronic excitation of Si and fluorinated Si in the surface layers. These centers are quenched by majority carriers.
Laser Direct Writing of Optical Interconnects in Polyimides and Sio2:TiO2 Coatings
Authors: Hewak D.W. , Jerominek H. 
Published: March 2011

ABSTRACTCommercially available polyimides and SiO2:TiO2 coatings are experimentally studied for their potential application in optical guided-wave interconnect networks. Optical properties are measured, including transmission spectra, refractive index and loss, with the aim of determining the materials most suited for this application. On the most promising candidates, direct writing of strip waveguides with Ar-ion laser at 514.5 and 457.9 nm was performed. Localized thermal curing by writing with speeds up to 250 microns per second allows the achievement of multimode guiding structures. Light propagation loss measurements reveal that attenuation in strip waveguides is of the same order as in slab structures of the same material, typically 5-10 dB/cm at 633 nm.
Double Crystal X-Ray Diffraction Measurement of a Triclinicly Distorted and Tilted AlxGa1-xAs Unit Cell Produced by Growth on Offcut GaAs Substrates
Authors: Leiberich A. , Levkoff J. 
Published: March 2011

ABSTRACTCorrections are required for double crystal X-ray diffraction characterization of epitaxial AlxGa1-xAs layers grown on offcut GaAs (100) substrates. Double crystal X-ray diffraction measurements show that the cubic film unit cell defined by Vegard's law is triclinicly distorted and tilted with respect to the substrate unit cell. The distortion and tilt angles oppose each other defining a crystal geometry where the substrate and film <100= axes remain approximately coplanar with the surface normal. This film/substrate crystal geometry leads to formulation of a model describing heteroepitaxy on offcut (100) substrates. When film atoms are bonded to an offcut substrate, the already tetragonaly distorted film unit cell is subjected to additional cell distortions. The magnitude of this additional strain depends on where the film atoms are positioned on a substrate terrace. The first few layers of film atoms establish swain grades across individual substrate terraces. Constrained by the geometry of this interface region and driven by strain relaxation in the net growth direction, subsequent heteroepitaxy forms the measured film/substrate crystal geometry.
Interface Strain and the Valence Band Offset at the Lattice Matched In0.53Ga0.47As/InP (001) Interface
Authors: Hybertsen Mark S. 
Published: March 2011

ABSTRACTTotal energy minimization calculations show that the interface bonds are strained in nominally lattice matched In0.53 Ga0.47As/InP (001) heterostructures, in agreement with recent X-ray measurements. Anion intermixing relieves the interface strain. The calculated valence band offset varies with the interface bond lengths so the minimum energy structure must be used for a given composition. Then the calculated offset is independent of composition and is in good agreement with experiment. A simple model exhibits the qualitative features revealed by these calculations.
Atomic Structure of CaSi2/Si Interfaces
Authors: Walle Chris G. Van De 
Published: March 2011

ABSTRACTThe CaSi2/Si interface is studied with state-of-the-art first-principles calculations. Various models for the interfacial structure are examined, in which the Ca atoms at the interface exhibit 5-, 6-, 7-, or 8-fold coordination. The structures with sevenfold coordination (as in bulk CaSi2) have the lowest energy. However, the sixfold- and eightfold-coordinated structures are only ∼0.1 eV higher in energy. Schottky barrier heights are briefly discussed.
Growth Mode at the Ge/(1102) Sapphire Interface
Authors: Malafsky Geoffrey P. 
Published: March 2011

ABSTRACTThe growth mode of Ge on the (1102) surface of sapphire is explored with X-ray photoelectron spectroscopy. Ge exists in two bonding states at the interface, Ge-Ge and Ge-sapphire. Ge forms islands at submonolayer coverage for deposition temperatures of 25°C and 625°C. The formation of the islands is revealed by the rapid increase in the relative fraction of the Ge-Ge bonding state for Ge coverage less than 1 ML. The shift in the Ge-Ge peak binding energy to the bulk Ge value at less than i ML suggests that the islands are three dimensional for deposition at 625°C.
Xps Analysis of the Sapphire Surface as a Function of High Temperature Vacuum Annealing
Authors: Richmond E.D. 
Published: March 2011

ABSTRACTFor the first time the (1102) surface of sapphire has been investigated by X-ray photoelectron spectroscopy to ascertain chemical changes resulting from annealing in vacuum at 1300° C and 1450° C. As received substrates had a substantial surface C contaminant. For substrates that were chemically cleaned before inserting them into the MBE system no trace of carbon is detected. A residual flourine contaminant results from the cleaning procedure and is desorbed by the vacuum annealing. Spectra of annealed substrates are compared to the unannealed chemically cleaned substrates. The annealed substrates exhibit 0.4 to 0.5 eV shift to higher binding energy of the Al peak and a 0.3 eV shift to higher binding energy of the O peak. In addition, a 2% depletion of oxygen from the surface occurs.
Role of Tip Material in Scanning Tunneling Microscopy
Authors: Chen C. Julian 
Published: March 2011

ABSTRACTIn this paper, we show that atomic resolution in scanning tunneling microscopy (STM) originates from pz or dz2 states on the tip. Consequently, only a limited selection of tip materials can provide atomic resolution: d-band metals, for example, Pt, Ir, Pd, Rh, W, Mo; semiconductors that tend to form p-like dangling bonds, for example, Si.
Theoretical Studies of GaAs on Si
Authors: Northrup John E. 
Published: March 2011

ABSTRACTThe energies of various two-dimensional GaAs on Si films have been calculated using the first principles pseudopotential method and density functional formalism. For GaAs on Si(111), the structures formed by adding a bilayer of GaAs to Si(111)1×1:As are shown to have positive formation energies, even after exchange reactions which eliminate the interface dipole are allowed. For GaAs on Si(100), the dependence of the formation energy of the films on the chemical potentials of the atomic constituents has been calculated. In the limit where μAs=μAs(bulk), and assuming the films have equilibrated with a bulk GaAs reservoir (μGa + μAs = μGaAs (bulk)), the lowest energy film is found to be the Si(100)2×1:As surface. In the opposite limit, μGa=μGa(bulk), the lowest energy film is the Si(100)2×1:(GaAs) surface. A new metastable structure obtained by adding 1/2 monolayer of Ga to Si(100)2×l:As has been studied.
A Weak Beam Imaging Technique for the Characterization of Interfacial Roughness in (InGa)As/GaAs Strained Layer Structures
Authors: Yao J. Y. , Andersson T. G. , Dunlop G. L. 
Published: March 2011

ABSTRACTA transmission electron microscope weak beam imaging technique has been developed for the characterization of interfacial roughness in lattice strained (InGa)As/GaAs multiple layered structures. In this technique, the heterointerfaces of (100) type strained layers are imaged in an inclined projection with a g311 diffracted reflection at off-Bragg conditions which gives an enhanced contrast from variations in strained layer thickness. A calculation based on the kinematic theory of contrast was made in order to gain a better understanding of the contrast. The calculation suggests that the observed contrast is due to monolayer scale variations in thickness of the strained layers.
Structure of a Near-Coincidence Σ9 Tilt Grain Boundary in Aluminum
Authors: Mills M. J. , Thomas G. J. , Daw M. S. , Cosandey F. 
Published: March 2011

ABSTRACTA systematic study of the structure of tilt grain boundaries in aluminum has been initiated. High resolution transmission electron microscopy is being used to examine the interface structure of several bicrystals with <110> tilt axes. In this paper, we report the structure determination of a grain boundary close to the Σ9 (221) symmetric orientation. The grain boundary plane, which appears wavy at lower magnification, is actually composed of atomically flat microfacets. Two distinct, symmetric structures with (221) boundary planes have been identified within individual microfacets. These observations have been compared with structures calculated using the Embedded Atom Method. The semi-quantitative comparison between the observed and predicted grain boundary structures is accomplished using multislice image simulations based on the calculated structures. The results of these comparisons and the evaluation of the relative energies of the microfacets are discussed.
A Leed Study of Bismuth Overlayer Formation on InSb(110)
Authors: Guo T. , Wan K. J. , Ford W. K. 
Published: March 2011

ABSTRACTLEED and Auger electron spectroscopy have been used to studied the interface formation of bismuth on InSb(110). For the first time, well defined superstructures were observed at room temperature on metal/semimetal-III-V semiconductors. A (1×2) phase, at 0.5 ML bismuth coverage, and a (1×3) phase, at 0.4 ML bismuth coverage, appear with different thermal heat cycling. The dynamical origin of these phases is thought to be a repulsive interaction between overlayer chains due to the detailed geometry of the overlayer chain structure and to the overlayer induced strain field within the substrate.
A Mechanism for Solute Segregation to Grain Boundaries
Authors: Youyi Chu , Sanhong Zhan 
Published: March 2011

ABSTRACTBased an the local equilibrium among vacancies, solute atans and vacancy-solute atom complexes, a mechanism for solute segregation to grain boundaries is suggested for a alloy system with binding energy of complex S≫kT. A set of dynamic equations for grain boundary segregation is ived, which can describe both equilibrium and nonequilibrium segregations, as the effect of the equilibrium segregation is taken into account in the bonndary condition. Theoretical calculation is made by computer for boron segregation at austenite grain boundaries as functions of isothermal holding time, cooling rate and quenching teaperature, which agree well with experimental results.
Simulation and Quantification of High-Resolution Z-Contrast Imaging of Semiconductor Interfaces
Authors: Jesson D. E. , Pennycook S. J. , Chisholm M. F. 
Published: March 2011

ABSTRACTIncoherent characteristics of Z-contrast STEM images are explained using a Bloch wave approach. To a good approximation, the image is given by the columnar high-angle cross-section multiplied by the s-state intensity at the projected atom sites, convoluted with an appropriate resolution function. Consequently, image interpretation can be performed intuitively and quantitative simulation can be implemented on a small computer. The feasibility of ‘column-by-column’ compositional mapping is discussed.
Simulated Image Maps for Use in Experimental High-Resolution Electron Microscopy
Authors: O'Keefe Michael A. , Dahmen Ulrich , Hetherington Crispin J.D. 
Published: March 2011

ABSTRACTA “map” of all possible high-resolution images may be simulated for a crystalline specimen in a chosen orientation for any particular transmission electron microscope (HRTEM). These maps are useful during experimental high-resolution electron microscopy and make it possible to locate optimum imaging conditions even for foil thicknesses beyond the weak-phase object limit. Although defects such as grain boundaries are not generally periodic, image maps of perfect crystal can be used to optimize defect contrast during operation of the microscope by reference to the image of the perfect crystal neighboring the defect.
High-Resolution Imaging of Coga/GaAs and Eras/GaAs Interfaces
Authors: Zhu Jane G. , McKeman Stuart , Palmstrøm Chris J. , Carter C. Barry 
Published: March 2011

ABSTRACTCoGa/GaAs and ErAs/GaAs grown by molecular-beam epitaxy have been studied using high-resolution transmission electron microscopy (HRTEM). The epitactic interfaces have been shown to be abrupt on the atomic scale. Computer simulations of the HRTEM images have been obtained for different interface structures under various specimen and image conditions. Practical problems in the comparison between the simulated and experimental images are discussed.
High-Purity Germanium Crystal Growing
Authors: Hansen W. L. , Haller E.E. 
Published: March 2011

ABSTRACTThe germanium crystals used for the fabrication of nuclear radiation detectors are required to have a purity and crystalline perfection which is unsurpassed by any other solid material. These crystals should not have a net electrically active impurity concentration greater than 10l0cm−3and be essentially free of charge trapping defects.Such perfect crystals of germanium can be grown only because of the highly favorable chemical and physical properties of this element. However, ten years of laboratory scale and commercial experience has still not made the production of such crystals routine. The origin and control of many impurities and electrically active defect complexes is now fairly well understood but regular production is often interrupted for long periods due to the difficulty of achieving the required high purity or to charge trapping in detectors made from crystals seemingly grown under the required conditions.The compromises involved in the selection of zone refining and crystal grower parts and ambients is discussed and the difficulty in controlling the purity of key elements in the process is emphasized. The consequences of growing in a hydrogen ambient are discussed in detail and it is shown how complexes of neutral defects produce electrically active centers.
Silicon Radiation Detectors - Materials and Applications
Authors: Walton Jack T. , Haller Eugene E. 
Published: March 2011

ABSTRACTSilicon nuclear radiation detectors are available today in a large variety of sizes and types. This profusion has been made possible by the ever increasing quality and diameter silicon single crystals, new processing technologies and techniques, and innovative detector design. The salient characteristics of the four basic detector groups, diffused junction, ion implanted, surface barrier, and lithium drift are reviewed along with the silicon crystal requirements. Results of crystal imperfections detected by lithium ion compensation are presented. Processing technologies and techniques are described. Two recent novel position-sensitive detector designs are discussed—one in high-energy particle track reconstruction and the other in x-ray angiography. The unique experimental results obtained with these devices are presented.
High-Voltage Operation of Surface Barrier Silicon Detectors With a Side Groove
Authors: Ohkawa S. , Husimi K. , Kim C. , Kim Y. , Itoh D. 
Published: March 2011

ABSTRACTA remarkable characteristic of the surface barrier detector with a side groove cooled down to the nitrogen temperature has been observed. That is an abrupt decrease of the output noise at a definite voltage in increasing the bias voltage slowly. This is caused by a carrier injection from the side surface of the groove near the neck narrowed by the side groove. This excess noise disappears after the depletion layer goes through the neck of the side groove. This is confirmed by the fact that the capacitance of the detector decreases abruptly with the decrease of the noise at the same bias voltage. This detector is capable to be operated at a voltage higher than this voltage with a low noise. The maximum bias voltage applied to the detector is 3000 V.
The Fabrication of Mercuric Iodide Detectors for Use in Wavelength Dispersive X-Ray Analysers and Backscatter Photon Measurements
Authors: Howes John H. , Watling John 
Published: March 2011

ABSTRACTThis paper describes the fabrication of mercuric iodide nuclear radiation detectors suitable for X and gamma ray spectrometry at room temperature. The active area of the detectors studied are between 0.2 and 1.5cm sq and they are up to 0.5mm thick. The method of producing a stable electrical contact to the crystal using sputtered germanium has been studied. The X-ray resolution of a 1.5cm sq. area detector at 32 keV is 2.3 keV FWHM when operated at room temperature in conjunction with a time variant filter amplifier. A factor which is important in the fabrication of the detector is the surface passivation necessary to achieve a useful detector life.This type of detector has been used on a wavelength dispersive X-ray spectrometer for energy measurements between 10 and 100 keV. The advantages over the scintillation counter, more commonly used, is the improved resolution of the HgI2 detector and its smaller size. The analyser is primarily used for the detection of low levels of heavy metals on particulate filters. The detectors have also been used on an experimental basis for gamma ray backscatter measurements in the medical field.