bluuebunny/crossref_metadata_2025 huggingface dataset:
Outgassing Characteristics of Stainless Steel and Aluminum with Different Surface Treatments
Authors: Young J. R.
Published: July 2002

The outgassing characteristics of 304 stainless steel with different surface treatments have been measured. The surface treatments investigated were: (1) glass-bead shot blasting; (2) electropolishing with a surface roughness of 20–25 μ in.; (3) electropolishing with a surface roughness of 4–6 μ in.; (4) one of the above treatments plus oxidation by baking in air at 250 ° or 450 °C; (5) treatment (2) above plus 450 °C bake under vacuum. The outgassing characteristics of type-1100 aluminum, which had been cleaned with detergent and rinsed with acetone, were also determined. Results obtained indicate the outgassing rates for stainless steel cleaned by glass-bead shot blasting or electropolishing after a 250 °C bake for 15–30 h are approximately the same and equal to 2×10−12 Torr liter/sec cm2. These results are in agreement with the results reported by Calder and Lewin. Oxidized stainless steel produced a lower outgassing rate between 3 and 5×10−13 Torr liter/sec cm2. Also, a 450 °C bake for 17 h of stainless steel with the inner surface exposed to vacuum exhibited an outgassing rate of 4×10−13 Torr liter/sec cm2. Aluminum baked at 250 °C for 15 h provided an outgassing rate of 4×10−13 Torr liter/sec cm2. These results are explainable on the basis of H2 depletion from the samples due to high temperature baking for long periods of time and also the lower H2 permeation through oxide films.
Effect of the eta layer on TiC-coated, cemented-carbide tool life
Authors: Sproul William D. , Richman Marc H.
Published: July 2002

Chemical vapor deposition of a thick film of TiC on a cemented carbide produces an intermediate layer, ∠1 μm thick, of Co6W6C (eta carbide) between the substrate and the 3-μm-thick TiC coating. Although the TiC-coated cemented carbides have a much longer tool life than an uncoated tool, the effect of the intermediate eta phase on this tool life has not been known to date. Normally, the eta phase is avoided in cemented carbides because of its brittleness, but it has been proposed that the eta carbide actually enhances the tool life by forming a diffusion barrier. This hypothesis is being investigated by preparing coated cemented carbides by sputtering. With this method, it is possible to prepare TiC-coated tools with and without the eta-carbide layer and study the effect of the eta carbide on tool life. Tool-life tests with eta-coated carbides show that the eta layer does improve tool life.
Growth and properties of vacuum deposited CuInSe2 thin films
Authors: Kazmerski L. L. , Ayyagari M. S. , White F. R. , Sanborn G. A.
Published: July 2002

The vacuum deposition of CuInCe2 thin films is reported. As-deposited films are generally n-type due to selenide deficiencies. The temperature dependence of film mobility, conductivity, and carrier concentration are presented and indicate the dominance of the grain-boundary scattering mechanism. Mobilities of the range 1–20 cm2/V s are reported for as-deposited films. Data are also presented for films annealed in Ar atmospheres. Films annealed in Ar/H2Se can be made p-type with mobilities in the range 1–8 cm2/V s. Electron and x-ray diffraction data are discussed. Grain size data, especially the consideration of the effects of substrate temperature, are included. Photoconductive decay times are reported for the films.
Magnetron sputtering: basic physics and application to cylindrical magnetrons
Authors: Thornton John A.
Published: July 2002

Magnetron sputtering sources can be defined as diode devices in which magnetic fields are used in concert with the cathode surface to form electron traps which are so configured that the E×B electron-drift currents close on themselves. Coaxial cylindrical magnetron sputtering sources in which post or hollow cathodes are operated in axial magnetic fields have been reported for a number of years. However, their performance is limited by end losses. A remarkable performance is achieved when the end losses are eliminated by proper shaping of the magnetic field or by using suitably placed electron-reflecting surfaces. High currents and sputtering rates can be obtained, nearly independent of voltage, even at low pressures. This characterizes what has been defined as the magnetron mode of operation. This paper reviews the basic principles that underly the operation of dc sputtering sources in the magnetron mode with particular emphasis on cylindrical magnetrons. The important attributes of these devices as sputtering sources are also reviewed.
Ion beam texturing of surfaces
Authors: Kaufman Harold R. , Robinson Raymond S.
Published: July 2002

Textured surfaces, typically with conical structures, have been produced previously by simultaneously etching a surface and seeding that surface with another material. A theory based on surface diffusion predicts a variation in cone spacing with surface temperature, as well as a critical temperature below which cones will not form. Substantial agreement with theory has been found for several combinations of seed and surface materials, including one with a high sputter yield seed on a low sputter yield surface (gold on aluminum). Coning with this last combination was predicted by the theory for a sufficiently mobile seed material. The existence of a minimum temperature for the formation of cones should also be important to those interested in ion-beam machining smooth surfaces. Elements contained in the environmental contaminants or in the sputtered alloys or compounds may serve as seed material.
Characterization of a sulfur-resistant methanation catalyst by XPS.
Authors: Shalvoy R. B. , Reucroft P. J.
Published: July 2002

A Ni–Cr on MgSiO3 catalyst has been developed by United Catalysts, Inc. This catalyst converts 60% of the input CO to CH4 after a heavy presulfiding treatment that reduces the CO conversion of conventional catalysts to less than 10%. The unsulfided conversion rate is better than 95%. X-ray photoemission spectra obtained from a series of untreated, sulfided, and methanation-tested Ni and Ni–Cr on MgSiO3 catalysts show the presence of nickel sulfide in catalysts which are deactivated by the sulfiding. Both nickel sulfide and nickel sulfate are found in the catalysts that retain appreciable methanation activity. The amount of sulfur in the active catalysts is also appreciably less than in the inactive catalysts. The relationship between the resistance to sulfur poisoning and the presence of Cr and MgSiO3 is discussed.
Advances in high precision sample positioning stages for electron-beam microfabrication and metrology
Authors: Pasiecznik J. , Reeds J.W. , Fralick R.D.
Published: July 2002

An improved computer controlled X–Y stage has been built for electron-beam microfabrication and metrology. The stage servo drives and the laser stage position sensors are mounted directly to the stage vacuum chamber to provide maximum rigidity. An ’’L’’ shaped chromium carbide mirror provides a reference with 1/4 arc-s accuracy for the stage position sensing laser, while allowing the sample to be in the plane of the laser beams to eliminate position sensing errors due to pitch and yaw of the stage. A reference chip is mounted on the stage in the plane of the sample to aid in initial focus and registration. For precision manual control of the stage a digital joystick is used. Nonlinear shaping networks on a standard linear taper joystick enable the operator to easily position the stage to 0.01 μm and still be able to move at full slew speed (1 cm/s). For each axis, V–F converters are used to convert the analog output of the shaping network to a digital pulse train which feeds a 24 bit closed loop servosystem. A digital tach is used for damping. Rate feedback is derived from the laser interferometer system rather than the conventional generator coupled to the servomotor. High torque motors are used for improved acceleration and dynamic braking. Servomotor-to-stage-drive coupling incorporates a friction lead screw to eliminate backlash. Under computer control, repeatability of positioning has been determined to be 0.01 μm. Accuracy is 0.01 μm/cm plus 0.005 μm/cm of stage travel (laser interferometer error).
Vibration analysis using the stripe scan method of a laser interferometer controlled X–Y table in an electron-beam system
Authors: Wilson A.D. , Studwell T.
Published: July 2002

The writing time of an electron-beam lithography system can be reduced by compensating for table vibrations and other position errors using error feedback from a laser intererometer to the electron beam. The beam may then write while the table is moving because the laser interferometer corrects for vibration of the table and mirror system. However, this may not represent the substrate motion because of relative movement between mirror and substrate. A stripe scan technique is used to identify these problems and to evaluate the sample securing system. The amplitude and frequency of vibration are easily determined as well as the correct value of laser interferometer servofeedback gain.
Electron beam exposure system
Authors: Pei-yong Qiu , Jian-kun Wang
Published: July 2002

An electron-beam exposing system, utilizing a computer generated pattern and used for microcircuit fabrication of high packing density, is described.
Inspection of complete VLSI chips with a high resolution image recording system and large area SEM
Authors: Rao V. R. M. , Nixon W. C.
Published: July 2002

This paper presents results that have been obtained from an electron-beam recording system that has been coupled to a large area coverage SEM and used for the inspection of VLSI chips with areas up to 5×5 mm. The recording system is capable of copying 10 000×10 000 picture points over negative areas of 50×50 mm in 50 s. In order to utilize fully the resolution capability of the recording system the SEM must also have a similar performance. To this end and SEM with post-final lens single deflection has been used to generate 10 000×10 000 picture point images of VLSI chips. These images have been copied onto photographic film using the scanning recording system. The advantages of the recording system lie in its ability to copy the images of complete chips with micron and submicron feature sizes directly onto photographic film in a single scan and in the relative ease with which the system can be linked to an SEM.
Adhesion of nickel films on graphite
Authors: Snyder J. R. , Smith M. A. , Levenson L. L.
Published: July 2002

Nickel dots from 0.8 to 1.6 mm in diameter and up to 500 nm thick were evaporated onto the stepped (0001) basal surface of stress-annealed pyrolytic graphite. Leads were soldered or glued to the as-deposited dots and increasing stress normal to the graphite basal planes was applied to the leads until rupture occurred, usually ≳1 MPa. The distribution of stress-at-failure data followed Weibull failure statistics. Auger electron spectroscopy (AES) of the fracture surface of dots ?200 nm thick showed only graphite. In-depth AES revealed that nickel carbide was present at the nickel–graphite interface. Samples annealed at 400°C for 2 h had a lower characteristic tensile strength than unannealed samples and separated at the interface where AES detected no nickel carbide.
Bit oriented optical storage with thin tellurium films
Authors: Lou David Y. , Blom Gerard M. , Kenney George C.
Published: July 2002

We discuss here some of the basic issues involved in the development of an optical storage medium based on the laser micromachining of thin tellurium films. Results are presented in the areas of recording sensitivity, materials resolution, error statistics, and archival stability. It is shown that a medium using 20–30 nm of tellurium deposited on polymethyl methacrylate substrates is an extremely attractive choice.
Secondary ion mass spectrometry analysis of semiconductor layers
Authors: Slusser G. J. , Slattery J. S.
Published: July 2002

The technique of Secondary Ion Mass Spectrometry (SIMS) is analyzed for its capabilities of monitoring layered structures. Primary ion beam current and secondary ion species are varied in order to minimize interface phenomena due to changes in ionization efficiences. It is noted that the choice of primary ion beam current can be particularly important when an oxygen bleed is used. Layer profiles are shown to become more complex when a secondary cluster ion is monitored instead of the monoatomic ion for species detection. With nitrogen as an example, quantitative analysis using cluster ions containing three or more atoms is shown to be extremely difficult, particularly when no oxygen bleed is used.
Electronic structure of GaAsxP1−x/GaP strained-layer superlattices with x<0.5
Authors: Osbourn G. C.
Published: July 2002

The electronic properties of GaAsxP1−x/GaP(100) strained-layer superlattices with x<0.5 are studied using both a tight-binding model and an effective-mass model. By varying the alloy compositions and thicknesses of the layers, it is possible to independently vary the band gap and lattice constant of these structures. For the structures in which the bulk [100] minima are mapped into the strained-layer superlattice Γ point, a direct band gap occurs in the superlattice even though the bulk materials have indirect gaps. The results illustrate that strained-layer superlattices in general form a broad new class of semiconductor materials with tailorable electronic properties.
Vacancies and hydrogen adsorption at GaAs(110): Theoretical model studies of the electronic structure
Authors: Beyer J. , Krüger P. , Mazur A. , Pollmann J. , Schmeits M.
Published: July 2002

We have carried out model calculations for the electronic properties of point perturbations at the relaxed GaAs(110) surface. The calculations are based on the tight-binding scattering theoretical method for semi-infinite solids. Ga and As vacancies at or near the surface and in the bulk crystal are discussed in terms of vacancy-induced changes in the local density of states. Comparison with the results of other vacancy calculations is made. H adsorption was investigated by studying a model system consisting of an atomic s level coupled to the GaAs(110) substrate. We discuss our results in terms of local densities of states at the adsorbate and at the nearest-neighbor substrate atom. Substrate-mediated interactions between different vacancies or between different adsorbed atoms are discussed, as well.
Sensitivity of capacitance diaphragm manometers to static magnetic fields
Authors: Dylla H. F. , Provost T. J.
Published: July 2002

The sensors of the two capacitance diaphragm manometers investigated in this study appear to have no significant dependence upon exposure to static magnetic fields. Subsequent use of the sensors in the near-field environment of the PDX tokamak showed the sensors could perform unshielded in a magnetic environment, however, it was found necessary to magnetically shield the associated signal-conditioning electronics.
Ion-beam-induced topography and surface diffusion
Authors: Robinson R. S. , Rossnagel S. M.
Published: July 2002

The development of surface microtexture along with ion-impact-enhanced surface and bulk diffusion processes is important for users of ion beams and plasmas for thin film or material processing. Even in those applications where texturing is not desired, an understanding of the process of texturing will permit proper corrective action when texturing is found to occur. Surface microtexturing produced using ion-beam sputtering and simultaneous deposition of impurities is described both in terms of a simple diffusion model and with regard to detailed studies of the initiation, development, and failure of individual sputter cones. Digital computer calculations are presented which follow surface feature development under sputtering. These calculations appear to confirm the role of ion reflection in the development of cones. A coating associated with the impurity deposition is often observed on individual cones. This coating appears to play a role both in the initial development of cones and in the subsequent evolution of second generation cones in a steady-state process. Surface diffusion, in excess of that expected from thermally activated diffusion alone, has been observed as the ion-beam current density is increased. This impact-enhanced diffusion appears to depend on cooperative effects between multiple ion impacts.
Variation of the threshold energies for core-electron excitation in electron energy-loss spectra as a function of incident electron energy
Authors: Erickson N. E. , Powell C. J.
Published: July 2002

Measurements have been made of the 3p, 3s, and 2p core-electron energy-loss spectra of Ti and Ni as a function of incident electron energy. Attention was focused on the threshold energy for core-level ionization to investigate possible changes in the threshold energies as a function of excitation conditions. Measured threshold energies decreased by between 0.1 and 1.5 eV, depending on the specific core level, as the incident electron energy was lowered from about 1500 to about 20–50 eV above the core threshold. The measured changes in threshold energies are due in part to different core-electron binding energies for bulk and surface atoms, to varying populations of final states, and to dynamical screening effects. These factors can account for differences in binding energies measured by x-ray photoelectron spectroscopy and by appearance potential spectroscopy.
Vacuum applications for the Tritium Systems Test Assembly
Authors: Anderson James L. , Coffin Don O. , Walthers Charles R.
Published: July 2002

The Tritium Systems Test Assembly (TSTA) is a facility which will develop and demonstrate the processes for handling the fuel and exhaust from a magnetic fusion reactor using deuterium and tritium as the fuel. The TSTA facility became operational in mid 1982 and will now proceed to test and evaluate the many subsystems required to purify, separate, circulate, and reuse the deuterium/tritium gas recovered from the reactor vacuum system. At TSTA the reactor will be simulated by a large vacuum vessel into which mixtures of deuterium, tritium, and various impurities (He, CH4, H2O, NH3, C2H2) are injected. This mixture is then exhausted through the vacuum system, reprocessed and prepared for reinjection into the front end. A fusion reactor must have an enormous vacuum system to remove the mixture of fuel and impurites so that the plasma can be replenished with fresh fuel. At TSTA this evacuation is achieved with ‘‘compound’’ cryopumps. These pumps remove the deuterium and tritium by cryocondensation on a 4-K panel. The helium is removed by cryosorption on a separate refrigerated panel. TSTA will provide the first opportunity to test several models of compound cryopumps with actual mixtures of deuterium, tritium, and helium. This paper will discuss the role TSTA has in the national magnetic fusion energy program with special emphasis on the vacuum system and preliminary experimental results.
Theory of electronic structure of copper overlayers on transition metal substrates
Authors: Ma C. Q. , Ramana M. V. , Cooper B. R. , Krakauer H.
Published: July 2002

We have used our recently developed self-consistent film-linearized muffin-tin orbital (FLMTO) technique to calculate the band structure and corresponding layer projected density of states for systems consisting of a monolayer of copper on top of a transition metal substrate. The two systems which have been considered (using five-layer slab geometries) and compared to pertinent experiments are (111)Cu on (0001)Ru and (100)Cu on (100)Ni. For the Cu monolayer on Ru we obtain close agreement with the experimentally observed (via UPS) downward shift (compared to bulk copper behavior) of the top of the copper d bands relative to the Fermi energy. Also there is charge transfer from the interface ruthenium to the surface copper. For Cu/Ni, the theoretical behavior reproduces the experimentally observed (via EELS) filling and narrowing of the surface d bands.
Temperature effects on the formation of a uniform liquid layer of hydrogen isotopes inside a spherical cryogenic ICF target
Authors: Mok L. , Kim K. , Bernat T. P. , Darling D. H.
Published: July 2002

The effects of temperature gradient on the behavior of liquids of hydrogen isotopes inside a spherical ICF target are theoretically investigated. Two models are developed. In the first model, only the effect of the surface tension gradient induced by a nonuniform external temperature field is considered. As a result, other temperature-induced effects, such as the mass transfer across the liquid–gas interface and the nonuniformity in the density, pressure, and viscosity of the fluids, are not included. The second model considers the additional effect created by the mass transfer, namely, the effect of condensation and evaporation. The net result in both cases is an expression for the temperature gradient at the target exterior which will sustain a uniform liquid layer of hydrogen isotopes inside a spherical ICF target.
Plasma edge studies in ISX-B and EBT-S using surface probes and laser-induced fluorescence
Authors: Roberto J. B. , Clausing R. E. , Dullni E. , Emerson L. C. , Heatherly L. , Schweer B. , Withrow S. P. , Zuhr R. A.
Published: July 2002

Results of recent plasma edge experiments using surface collection probes and laser-induced fluorescence in the ISX-B tokamak and EBT-S bumpy torus are summarized. Data are presented for ion temperatures and fluxes, neutral fluxes and energies, impurity fluxes and introduction mechanisms, and erosion and redeposition rates. Comparison is made where possible with results from other plasma diagnostics. It is found that the edge ion temperature is ∼20 eV in these devices (comparable to the edge electron temperature) and that wall sputtering (by charge exchange neutrals in ISX-B and self-ions in EBT-S) is the dominant heavy impurity introduction mechanism.
RGA system for the NSLS
Authors: Schuchman J. C. , West L. J.
Published: July 2002

The National Synchrotron Light Source (NSLS) is a synchrotron radiation source designed to provide photons for simultaneous experiments on a large number of individual beam lines. A residual gas analysis (RGA) system has been designed, and is currently being installed, which would protect the beam lines and the storage rings from contamination from any one offending beam line. The system consists of having separate analyzers, with their associated rf generators, in each beam line and storage ring. The analyzers will be multiplexed back to a central controller. A computer is used for routine monitoring and control. The analyzer chosen was the VG Instruments Model SX-200. Typical mass spectra will be presented along with our specifications for the RGA and our vacuum specifications for operating a typical beam line.
Photoemission studies of atomic redistribution at gold–silicon and aluminum–silicon interfaces
Authors: Brillson L. J. , Katnani A. D. , Kelly M. , Margaritondo G.
Published: July 2002

We have used soft x-ray photoemission spectroscopy (SXPS) to monitor the rearrangement of Si and metal atoms during the initial stages of Au or Al interface formation with UHV-cleaved (111) or (100) Si surfaces. From Si 2p core level spectra as a function of metal overlayer thickness and as a function of incident photon energy, we obtain evidence for strong Si bond changes at submonolayer Au coverages but only weak Al–Si interactions. Marker experiments reveal that Au diffuses into Si (Si diffuses into Al) with the first few deposited metal overlayers. We examine our new information on the interface evolution at room and elevated temperatures in relation to the corresponding bulk phase diagrams.
Crystallographic anisotropies in the formation and oxidation of carbon on nickel
Authors: Caracciolo R. , Schmidt L. D.
Published: July 2002

A curved nickel single crystal exposing the [100]–[111]–[110] zone was used to study crystallographic variations in the formation and oxidation of surface carbon formed by exposing the crystal to ethylene at 0.1 Torr and 550 K for 300 s. The crystal was transferred directly into a UHV system where AES was used to monitor the carbon density and type. The crystal was rotated in front of the AES electron beam to scan orientations at ∼5° intervals with 2° resolution. After ethylene exposure at 0.1 Torr, the carbon signal was independent of crystallographic orientation except for the (100) plane where it was ∼50% lower. Upon heating this surface to 800 K at 1×10−9 Torr the carbon signal increased by approximately 300% on the (100), (111), and (110) planes, whereas on the high index planes it remained unchanged. Carbon was removed by heating in O2 at 10−7 Torr at 800 K and the surface was scanned at regular time intervals. The (100) and (111) planes show approximately first order removal kinetics in carbon, while on the (110) plane and on the high index planes the reaction mechanism is autocatalytic with an induction period followed by rapid removal of carbon.
Cryopump speed measurement with the AVS/ASTM and ISO test domes
Authors: Hood Charles B.
Published: July 2002

Correction factors are presented for speed measurement of cryopumps using nude ionization gauges, which take into account the effects produced by the reflection of gas molecules from the cold surface of the cryopump
Vacuum chamber for edgeless studies of gas–metal reactions
Authors: Patterson R. G. , Musket R. G.
Published: July 2002

The concept, design, construction, and operation of a high vacuum reaction chamber are described. This chamber eliminates specimen edge effects, permits studies of the quantitative kinetics of gases reacting with the surfaces of disklike specimens, and is well suited for evaluation of various schemes (e.g., coatings, ion implantations) designed to protect practical surfaces from the gases. Operation of the chamber has been demonstrated for the hydriding of depleted uranium in 76 Torr of hydrogen at 130 °C.
Angular resolved x-ray photoelectron spectroscopy study of reactively sputtered titanium nitride
Authors: Ernsberger C. , Nickerson J. , Miller A. E. , Moulder J.
Published: July 2002

Moisture and O2 levels present during the reactive sputtering deposition of TiN have a marked impact on measured contact resistance. Results of an angular resolved x-ray photoelectron spectroscopy (XPS) study of sputter deposited TiN as well as Auger electron spectroscopy (AES) show that oxynitrides are the predominant surface species on TiN. Two distinct oxynitride phases with different oxygen contents have been observed on TiN and the relative abundance of each phase appears to be a function of H2O and oxygen levels present during reactive sputtering.
Computational design of wear coatings
Authors: Kramer Bruce M. , Judd Patrick K.
Published: July 2002

Quantitative models for the relative abrasive and chemical dissolution wear rates of potential tool coating materials are presented. Inputs to the models include the free energy of formation of the tool material, the excess free energies of solution of the constituent elements of the tool material in the workpiece, the hardness of the coating, and the cutting temperature. The models have been implemented on a VAX 11/750 minicomputer to allow screening of candidate materials for improved wear coatings. Sample calculations are included and suggest that it may be possible to develop coatings with significantly better performance than current titanium nitride coatings.
Tungsten carbide phase transformation during the plasma spray process
Authors: Tu D. , Chang S. , Chao C. , Lin C.
Published: July 2002

Tungsten carbide coatings applied by the plasma spray process have been widely used in wear applications. In the W–C–Co ternary system, tungsten carbide can either be present as WC or W2C. Frequently WC transforms into W2C during the plasma spray process. In this study, tungsten carbide/17% cobalt coatings were applied by both the air plasma and the vacuum plasma spray processes using different power levels and plasma gases. The W2C phase was found by X-ray diffraction techniques in the air plasma sprayed coatings. Decarburizing of the WC in the presence of the oxygen took place in the plasma. In this study air plasma sprayed coating hardness and microstructure are superior to those of the vacuum plasma sprayed ones. However the vacuum plasma coatings were found to be more wear and impact resistance than the air plasma coatings. This performance difference may be attributed to the presence of hard and brittle W2C phase in the air plasma sprayed tungsten carbide coatings.
An axial-emission magnetron ionization gauge
Authors: Chen J. Z. , Suen C. D. , Kuo Y. H.
Published: July 2002

The axial-emission ionization gauge (AEG) has been modified to form an axial-emission magnetron ionization gauge (AEMG) by adding an axial magnetic field to the electrode construction of the AEG. This modification results in a much lower limiting measurable pressure. AEMG gives performances like that of Lafferty’s hot-cathode magnetron ionization gauge (LHMG) but the ratio of the x-ray photocurrent to the anode current Ix/Ia is smaller by more than two orders, so its lower limit is lower than that of LHMG. The upper limit of measurable pressure can be extended to 1.33×10−2 Pa (1×10−4 Torr) by operating the AEMG without the magnet. Since the electrode construction of AEMG is very simple, it is easy to de-gas and this is of benefit to its operation under extremely high vacuum.
Photostimulated molecular layer epitaxy
Authors: Nishizawa Jun-ichi , Abe Hitoshi , Kurabayashi Toru , Sakurai Naoki
Published: July 2002

The quality of GaAs epitaxial layers prepared by molecular layer epitaxy (MLE) with and without UV light irradiation was studied and appears to be a promising method for preparing the GaAs thin layers with an atomic order accuracy. Namely, single layer-by-layer growth has been realized for GaAs using AsH3 and trimethyl (TMG), and triethyl (TEG), gallium. Substrate temperature of 500 °C for TMG and AsH3, and 300 °C for TEG and AsH3 fulfilled the conditions for monolayer growth, where the film growth thickness per cycle corresponding to 2.83 and 3.26 Å for (100) and (111) B faces, respectively, are nearly saturated independently of the gas admittance quantity. Influences of photoirradiation on the film growth have been investigated by use of excimer lasers and Hg lamps. UV light irradiation improved the surface morphology and in certain instances also improved impurity concentrations. Conditioned photoirradiation—light beam synchronized with the time duration of AsH3 admittance, MO-gas admittance, and evacuation of gaseous molecules—was studied.
Intrinsic interface states and defect states for Si/NiSi2(111)
Authors: Lim Hunhwa , Allen Roland E.
Published: July 2002

The intrinsic interface states and the states associated with interfacial vacancies have been calculated for the type A Si/NiSi2(111) interface. A prominent band of intrinsic interface states is predicted near and below the Si valence band maximum, Ev, dispersing downward from an energy in the Si band gap to an energy about 1 eV below Ev. This band should be observable in photoemission experiments. Our calculation for the interfacial Si vacancy on the NiSi2 side of the interface yields a level, a few tenths of an electron volt above the valence band edge, that can explain observed Schottky barriers at Si/NiSi2(111) interfaces.
Surface topography of Ar+ bombarded GaAs(100) at various temperatures
Authors: Bhattacharya S. R. , Ghose D. , Basu D. , Karmohapatro S. B.
Published: July 2002

Topographical changes in the surfaces of GaAs (100) crystal by Ar+ beam sputtering at various temperatures are studied. It is found that the bombarded surface remains almost featureless in contrast to similar sputtering of metal targets where conical protrusions always appear. However, cones do appear at high temperature with simultaneous seeding with Cu. The results are discussed with a view of Wehner’s recent investigations in the development of conical structures.
The structures and interfaces of TiN films prepared by hollow cathode discharge ion plating technique
Authors: Pengxing Li , Meihua Zhang , Xuan Qi , Xingfang Lin , Fan Yang
Published: July 2002

Two groups of Ti–N films were studied: one was deposited by hollow cathode discharge (HCD) onto high-speed steel and 18–8 stainless steel with different N2 flow rates in order to investigate the influence of Ti/N ratio and the kind of substrate on the structure, the other was first deposited onto as-annealed GCr15 (steel 52100) by HCD and magnetron sputtering, respectively, and then quenched in Ar atmosphere, with the aim of studying the changes in structures of coatings and the interfacial regions during heat treatment, and to compare the influence of different physical vapor deposition methods. The crystallographic features of structures and residual stress of TiN films were examined by x-ray diffraction. Auger electron spectroscopy and x-ray photoelectron spectroscopy were used to determine their composition and to characterize the features of interfacial regions. It was found that the coatings consist mainly of TiN phase. With decreasing N2 flow rate, Ti2N phase appeared and the microhardness increased as well, and the preferred orientation axis, vertical to the film plane, changed from (200) to (113) and then to (111). A tensile residual stress was found in the coatings. There was no evidence for a change in structures or of interfaces of TiN coatings on GCr15 steel after subsequent heat treatment.
Relative sensitivities of Bayard–Alpert gauges and a quadrupole mass spectrometer for hydrogen isotope molecules
Authors: Watanabe Kuniaki , Miyake Hitoshi , Matsuyama Masao
Published: July 2002

To apply mass spectrometers and ionization gauges to thermonuclear fusion devices such as pressure gauges, we measured the relative sensitivities (normalized to H2) of Bayard–Alpert (B–A) gauges (UGD-1S and UGS-1A, ANELVA Co.) and a quadrupole mass spectrometer (MSQ-150A, ULVAC Co.) for hydrogen isotopes. In the case of the B–A gauges, the relative sensitivities were determined as RHDB=1.07, RD2B=0.99, RHTB=1.03, RDTB=0.97, and RT2B =0.95. In the case of the quadrupole mass spectrometer, they were RHDM =1.09, RD2M =0.99, RHTM =1.06, RDTM =0.96, and RT2M =0.88. These values agreed quite well with those observed by Dibeler et al. for the mass spectrometer of the magnetic deflection type. It was revealed that the relative sensitivities of the quadrupole mass spectrometer were essentially the same as those for the B–A gauges except T2.
Characterization of fully lattice-matched multilayer ZnHgCdTe structures grown by Te-rich liquid phase epitaxy
Authors: Carlson R. A. , Hager R. J. , Wood R. A.
Published: July 2002

We report on the growth and characterization of fully lattice-matched multilayer ZnHgCdTe epilayers grown by Te-rich liquid phase epitaxy on lattice-matched CdTeSe substrates. Layers are characterized using Bond diffractometer x ray for lattice constant, IR transmission for composition, and energy dispersive x-ray and secondary ion mass spectroscopy for elemental depth profiling. Lattice parameters are reported for CdTeSe as a function of the CdSe mol % and for ZnHgCdTe as a function of the wt. % of Zn added to x=0.31 HgCdTe growth material. The segregation coefficient of Zn is also reported.
Rugate filters by laser flash evaporation of SiOxNy on room-temperature polycarbonate
Authors: Bartholomew C. S. , Morrow M. D. , Betz H. T. , Grieser J. L. , Spence R. A. , Murarka N. P.
Published: July 2002

A deposition system for laser flash evaporation was assembled and used to deposit onto polycarbonate SiOx Ny rugate filters with optical densities as high as 2.5 and bandwidths as low as 6.8% of the rejection wavelength.
Investigation of the void structure in amorphous germanium thin films as a function of low-energy ion bombardment
Authors: Yehoda J. E. , Yang B. , Vedam K. , Messier R.
Published: July 2002

Amorphous germanium thin films were prepared by electron-beam evaporation with low-energy Ar ion assist. The ion energy and ion/atom arrival rate ratio were varied from 15 to 110 eV and between 0% and 25%, respectively. The low-density ‘‘void’’ network structure was observed by transmission electron microscopy and characterized by spectroscopic ellipsometry. The void content of the films was shown to depend strongly on the ion/atom arrival rate ratio and to a lesser extent on the incident ion energy. A more quantitative description of thin-film evolution and important factors which affect it are discussed.
The organometallic epitaxy of extrinsic p-doped HgCdTe
Authors: Taskar N. R. , Bhat I. B. , Parat K. K. , Terry D. , Ehsani H. , Ghandhi S. K.
Published: July 2002

Extrinsic p-doped mercury cadmium telluride (MCT) layers have been grown by organometallic vapor phase epitaxy, using arsine in hydrogen as the dopant gas. Controllable doping in the range 3.5×1015–4.3×1016 was obtained when grown on GaAs with CdTe buffer layers. Consistently higher doping concentration (a factor of 2 to 4) was observed when a CdTe substrate was used. This is believed to be due to higher dislocation densities present when grown on GaAs, around which As may segregate. The cadmium fraction fell at very high flow; we believe that this is due to the prereaction of dimethylcadmium with arsine. Isothermal annealing under a Hg-rich ambient of MCT grown on CdTe substrates did not produce significant changes in the measured doping concentration. This indicates that the acceptor level is extrinsic in nature and that arsenic behaves as a stable acceptor dopant in MCT. The activation energy of this acceptor was determined as a function of doping, and is about one-half the value of the acceptor due to the Hg vacancies.
Alumina films by sputter deposition with Ar/O2: Preparation and characterization
Authors: Bhatia C. S. , Guthmiller G. , Spool A. M.
Published: July 2002

rf bias sputtered alumina thin films were produced under a variety of sputter conditions and analyzed for composition, thickness, density, and dielectric strength (breakdown field) in order to assess the affect of the inclusion of oxygen in the sputter gas on these films. All of the Al:O ratios for these films, as determined by Rutherford backscattering spectrometry, were lower than or equal to the ratio expected from stoichiometric considerations (0.67). In general, higher partial pressures of oxygen in the sputter system produced oxygen rich films. The Al:O ratios were found to vary from a high of 0.66 to a low of 0.54. These were found to correlate with the breakdown field measurements, with the oxygen rich films proving to be better insulators. Sputter bias was found to have the second greatest influence on dielectric strength. A sputter bias of −40 V in our sputtering system produced the best insulating films both in the presence and absence of oxygen in the sputter gas, with breakdown fields dropping off at lower and higher biases.
Interplay of erosion and redeposition processes in seed cone formation
Authors: Morishita S. , Okuyama F.
Published: July 2002

Cones developed on Cu surfaces bombarded with a focused Xe+ ion beam while simultaneously supplying Mo ‘‘seeds’’ by sputtering were observed by transmission electron microscopy. Cone morphology was found to depend heavily on the distance from the center of the ion beam, i.e., on the local ion-flux density; the shape was cone-like near the center, but less so farther from the center. In the central area, where the ion flux was largest, Mo layers were epitaxially grown on cone slopes, whereas the deposition of sputtered seed atoms on cone tops was enhanced in the peripheral area where the flux density was lowest. These findings indicate that the ion etching and the redeposition of sputtered seed atoms took place in a competitive manner, and the morphology and structure of the final cones were determined by the predominant process.
The characterization of titanium nitride by x-ray photoelectron spectroscopy and Rutherford backscattering
Authors: Vasile M. J. , Emerson A. B. , Baiocchi F. A.
Published: July 2002

X-ray photoelectron spectroscopy (XPS) spectra have been obtained for TiNx, with x=0.25, 0.50, and 1.0, as determined by Rutherford backscattering (RBS) analyses, and with no detectable oxygen content. We find the shape of the Ti 2p transition to be strongly dependent upon the nitrogen content, and interpret the spectrum as a mixture of Ti and TiN. TiN1.0 samples with varying oxygen content were also examined, and the oxygen content serves to increase the background step in the Ti 2p transition. Angle resolved measurements indicate that the inelastic scattering due to oxygen is superimposed over an intrinsic satellite structure in the Ti 2p transition. Atom ratios, N/Ti, cannot be accurately determined by XPS without standardization. The binding energy of the Ti 2p3/2 transition occurs at 454.5 eV and the N 1s transition occurs at 396.7 eV. The oxygen that is present in TiN at concentrations up to 12 at. % is most likely bound to Ti as TiO rather than TiO2. Valence band measurements agree well with previous reports.
Spectroscopic and spatial characterization of superconducting vortex core states with a scanning tunneling microscope
Authors: Hess H. F. , Robinson R. B. , Dynes R. C. , Valles J. M. , Waszczak J. V.
Published: July 2002

The Abrikosov flux lattice and individual superconducting vortices are imaged with a low temperature scanning tunneling microscope. Differential conductance measurements taken while scanning allow one to image the quasiparticle wavefunctions. Different quasiparticle energy states are highlighted by tunneling at different dc voltages. States which are bound to the vortex core are imaged by tunneling with a voltage below the superconducting gap energy. The lowest energy bound wavefunctions which exist at the fermi level show a radial extent of about a coherence length, while higher energy bound states display a more extended wavefunction. Likewise scattering states can be imaged by tunneling with voltages above the superconducting energy gap. The results are interpreted within the context of Bardeen–Cooper–Schrieffer theory.
Development of deuterated polystyrene shells for laser fusion by means of a density-matched emulsion method
Authors: Takagi M. , Norimatsu T. , Yamanaka T. , Nakai S.
Published: July 2002

High quality, microdeuterated polystyrene shells were fabricated using a density-matched emulsion method. The diameter and wall thickness of the shell ranged from 100 to 1500 and 3 to 15 μm, respectively. The sphericity, the wall thickness uniformity, and the surface smoothness were 99.8%, 99.3% and <0.1 μm, respectively. A defect on the inner surface of the shell was smeared by replacing water in the shell with ethanol prior to the final drying process.
X-ray photoemission study of the Ba/Si(100) interface and the oxidation of Si promoted by Ba overlayers
Authors: Mesarwi A. , Ignatiev A.
Published: July 2002

The interaction of barium overlayers with the Si(100) surface and the subsequent interface formation have been studied by x-ray photoelectron spectroscopy. Also studied, were the effects of Ba overlayers and the Ba/Si interface on the oxidation of Si at different Ba coverage (0≤θ≤2.4 ML) and different oxygen exposures. It is found that the Ba/Si interface formation follows a two-step mechanism. At low Ba coverage (θ≤2 ML), Ba deposits on top of, and strongly interacts with, silicon. This interaction is associated with charge transfer from the overlayer Ba atoms to silicon. Between 2 and 4 ML Ba coverage, the Ba/Si interface is unstable and silicon diffuses through the Ba overlayer. In addition, Ba overlayers on the Si(100) surface are found to significantly enhance the oxidation of silicon. At θ=2.4 ML Ba coverage, the obtained SiO2 oxides are found to be a factor of 5 thicker than those obtained for the clean unpromoted Si(100) surface.
Effects of hydrogen, nitrogen, and oxygen on the crystallographic and magnetic properties of sputtered (Co–Ni–Zr)/Cr thin film recording media
Authors: Suzuki Hiroyuki , Shiroishi Yoshihiro , Matsuda Yoshibumi , Ohno Tomoyuki
Published: July 2002

The effects of additive gases of hydrogen, nitrogen, and oxygen on the crystallographic and magnetic properties of sputtered (Co–Ni–Zr)/Cr thin film recording media have been studied. The results show that oxygen and nitrogen affect the coercive force more severely than hydrogen does. However, no significant changes in saturation magnetization are observed due to the introduction of additive gases during deposition. The in-plane epitaxial growth of a Co–Ni–Zr alloy magnetic layer on a Cr underlayer is degraded due to surface oxidation of the Cr underlayer by oxygen introduction and is also degraded due to lattice expansion of the Cr underlayer by nitrogen introduction.
Hydrogen profiling by elastic recoil detection in microcrystalline germanium thin films
Authors: Godet C. , Roca i Cabarrocas P. , Gujrathi S. C. , Burret P. A.
Published: July 2002

The elastic recoil detection technique improved by the time-of-flight is applied to the study of depth inhomogeneities in hydrogenated semiconductor thin films. The ex situ H profiling with a negligible H2O surface contamination (H surface peak) is made possible using a 300-Å-thick Al film evaporated on top of the sample. The H depth resolution is about 150 Å at the surface and is limited by straggling effects in the bulk. Microcrystalline germanium (μc-Ge:H) thin films have been obtained at low temperatures (423 and 523 K) from the plasma enhanced chemical vapor deposition using GeH4 diluted at 0.27% in H2. An increase of the crystallinity of the μc-Ge:H films vs distance to the substrate is observed. Depending on the deposition temperature, some films show a surface (300 Å) H content excess or depletion, attributed to effusion and trapping of molecular hydrogen into internal voids, during the deposition.
Novel system for maintaining window cleanliness in pulsed laser photochemical deposition reactors
Authors: Simpson J. , Williams J. O.
Published: July 2002

A device which allows the continual passage of pulsed laser radiation into a photochemical deposition chamber without the need for a purge gas is described. The laser beam is loosely focused on the window surface to ablate any deposited material, which is then caught in an electrostatic trap to avoid contamination of the film growth.
Low temperature etching of silicon trenches with SF6 in an electron cyclotron resonance reactor
Authors: Watts A. J. , Varhue W. J.
Published: July 2002

Trenches were etched in silicon with SF6 in an electron cyclotron resonance reactor. Etch rate and etch anisotropy were increased with radio-frequency substrate bias. Etch anisotropy was also improved by lowering the temperature of the substrate to −100 °C. Optical emission spectroscopy was used to measure the concentration of free fluorine in the plasma stream. Etch rate measurements were correlated to fluorine concentrations.
Film deposition with a facing magnets magnetron sputtering method
Authors: Fan Qihua , Chen Xiaohong , Chen Hongyou , Hong Yuan
Published: July 2002

A new type of cathode sputtering apparatus with two annular magnets facing each other has been developed. It cannot only deposit films at high rate and low substrate temperature but also greatly improve the target utilization and film thickness uniformity. The maximum deposition rate of Cu films was about 12 000 Å/min. The substrate temperature was not elevated above 55 °C during sputtering. Target utilization rate was improved to about 54%. For a target of 80 mm in diameter, the uniformity of Cu film thickness was better than ±5% over a region of about 56 mm in diameter.