bluuebunny/crossref_metadata_2025 huggingface dataset:
Automated computer analysis of x-ray radiographs greatly facilitates measurement of coating thickness variations in laser fusion targets
Authors: Stupin D. M. , Moore K. R. , Thomas G. D. , Whitman R. L.
Published: July 2002

We have built an automated system to analyze x-ray radiographs of laser fusion targets which greatly facilitates the detection of coating thickness variations. Many laser fusion targets require opaque coatings 1 to 20 μm thick which have been deposited on small glass balloons 100 to 500 μm in diameter. These coatings must be uniformly thick to 1% for the targets to perform optimally. Our system is designed to detect variations as small as 100 Å in 1-μm-thick coatings by converting the optical density variations of contact x-ray radiographs into coating thickness variations. Radiographic images are recorded in HRP emulsions and magnified by an optical microscope, imaged onto television camera, digitized and processed on a Data General S/230 computer with a code by Whitman. After an initial set-up by the operator, as many as 200 targets will be automatically characterized.
Radiation effects in materials for fusion reactors
Authors: Scott J. L. , Grossbeck M. L. , Maziasz P. J.
Published: July 2002

The 14-MeV neutrons produced in a fusion reactor result in different irradiation damage than the equivalent fluence in a fast breeder reactor, not only because of the higher defect generation rate, but because of the production of significant concentrations of helium and hydrogen. Although no fusion test reactor exists, the effects of combined displacement damage plus helium can be studied in mixed-spectrum fission reactors for alloys containing nickel (e.g., austenitic stainless steels). The presence of helium appears to modify vacancy and interstitial recombination such that microstructural development in alloys differs between the fusion and fission reactor environments. Since mechanical properties of alloys are related to the microstructure, the simultaneous production of helium and displacement damage impacts upon key design properties such as tensile, fatigue, creep, and crack growth. Through an understanding of the basic phenomena occurring during irradiation and the relationships between microstructure and properties, alloys can be tailored to minimize radiation-induced swelling and improve mechanical properties in fusion reactor service.
Organic getter for tritium
Authors: Souers P. C. , Bissell E. R. , Honoré G. D. , Kang L. C. , Tsugawa R. T. , Miller H. H.
Published: July 2002

Liquid and solid acetylenes on supported platinum catalysts have been studied in an effort to getter 1 ppm T2 from 1 at. air and nitrogen gas at room temperature. The results have not been successful, as only 0% to 15% of the tritium ends up in the organic phase, and there is no guarantee that hydrogenation takes place. Tritiated water is formed as the major product either by direct reaction with oxygen or exchange with background water.
AVS short courses for scientists, engineers, and technologists: Past and future
Authors: Harwood V. J. , Czanderna A. W.
Published: July 2002

A short course taught intensively for one, two, or five days is the most important of several media used by the Education Committee of the AVS to disseminate educational material about subjects of interest to the Society. The historical development of short courses is traced from offering one course to 80 registrants in 1969 to an availability of 29 courses that were taught to over 1200 persons in 1981. For these 12 years, data are given for the course titles, year(s) offered, number of registrants for each course taught, and location of the short courses. The number of registrants and short courses offered by local Chapters and Divisions are given for 1979–1981, and the cosponsorship role played by the Education Committee to assist Chapters is outlined. The course offerings demonstrate a responsiveness to the needs of the membership, Chapters, and Divisions of the AVS as well as the vacuum industry at large. Since mid-1978, 400 of the 1300 new members of the Society have been gained directly from the short course program. Future plans and prospects for service to the AVS membership and the scientific and technological community-at-large are outlined, especially the possibility of video taped courses. The importance of maintaining a strong set of short course offerings for the local Chapters and Divisions as well as the AVS as a Society is included in the discussion.
Electrical and optical properties of n-CdS/P–Si and n(Znx– Cd1−x)S/P–Si heterojunction solar cells
Authors: Abou Elfotouh F. A.
Published: July 2002

The electrical and optical properties of n-CdS/P–Si and n(Znx– Cd1−x)S/P–Si heterojunction are studied. The resistivity and optical reflectivity of the evaporated films are found dependent on substrate temperature, substrate surface preparation, and subsequent heat treatment. The resistivity is reduced by two orders of magnitude from its as-grown value (2×103 Ω cm) due to annealing in H2S. The density of charge carriers in the film and their mobility are controlled through Zn content, annealing temperature, and ambience. Junctions with 9% and 11% conversion efficiency are prepared from CdS and mixed sulfides, respectively. Higher efficiency is expected from future work due to improved preparation techniques.
The bonding properties of mercury–cadmium telluride
Authors: Harrison Walter A.
Published: July 2002

Recently developed bonding theory, applied to HgTe and CdTe, predicts the elastic and plastic rigidity of the two compounds relative to each other and relative to silicon.
Mechanisms of electron stimulated desorption from soda–silica glass surfaces
Authors: Wang Y. X. , Ohuchi F. , Holloway P. H.
Published: July 2002

Electron stimulated desorption from soda–silica glass surfaces has been investigated. It was shown that Na+, O+, and Si+ desorbed from the surface as well as other species from impure or corroded surfaces. The mechanisms of desorption include both interatomic and intra-atomic Auger deexcitations. For example, Na+ desorbed from core holes created either in the O level or in the Si 2p levels, while O+ and Si+ desorbed from core holes created in the O 1s level. Si+ desorbed only after electron bombardment created a Si-rich surface layer.
An x-ray photoelectron and electron energy loss study of the oxidation of lead
Authors: Taylor J. Ashley , Perry Dale L.
Published: July 2002

Lead–oxygen compounds and the exposures of clean polycrystalline Pb0 to O2, H2O, and air at various temperatures have been studied with x-ray photoelectron (XPS) and electron energy loss (EELS) spectroscopies. Results indicate that the shape of the Auger O KVV lines and EELS are sufficiently different to distinguish PbO, PbO2, Pb3O4, and carbonate–hydroxide. Differences in the EELS spectra indicate that orthorhombic PbO is formed on clean Pb0 exposed to dry O2 at temperatures below the melting point of Pb0, and tetragonal PbO is formed at or above its melting point.
Calculated Auger yields and sensitivity factors for K
L
L–N
O
O transitions with 1–10 kV primary beams
Authors: Mroczkowski Susan , Lichtman David
Published: July 2002

Relative values of the calculated Auger yields for the major KLL, LMM, MNN, and NOO transitions are listed for those transitions initiated by 1, 3, 5, and 10 kV primary electron beams. Additionally, these values are normalized to sensitivity factors in the Handbook of Auger Electron Spectroscopy for the specific transitions and primary voltages. The calculated yields can be used for quantitation if the Auger spectra were collected in the N(E) mode; the yields which have been normalized to Handbook values attempt to account for different derivative peak shapes and can be used for quantitation if the Auger spectra were collected in the dN(E)/dE mode. A discussion of the assumptions used in the calculated values outlines the cases in which care must be used. Internal calibration is recommended for accurate quantitation of transitions with an energy less than 200 eV.
Structure of Ti/SiO2 thin multilayers sputtered in argon–hydrogen mixtures
Authors: Yachi T.
Published: July 2002

A technique for preparing metal (Ti)/insulator (SiO2) thin multilayers by simultaneously performing sputtering from two independent sources in argon–hydrogen mixtures is described. Structural studies carried out by x-ray diffraction and Auger electron spectroscopy indicate a well-defined multilayer structure. The periodicity of the Ti/SiO2 thin multilayer is found to advance as a result of annealing at 400 °C. The preferred orientation in the Ti layers of the Ti/SiO2 thin multilayer changes due to the inclusion of hydrogen in the sputtering gas and a subsequent annealing at 400 °C.
Creation of tailored surfaces using selective oxidation of ion-implanted materials
Authors: Brown D. W. , Musket R. G. , Weirick L. J.
Published: July 2002

Ion implantation can produce a subsurface layer composition very different from that of the bulk material. The present work involves postimplant selective-oxidation treatments to produce a tailored surface composition. Formation of Al2O3-rich layers on both pure iron and 304-L stainless steel was achieved by implanting aluminum and subsequently heating the implanted sample in a controlled oxidizing environment to allow the subsurface aluminum to diffuse to the surface and oxidize. The thickness and composition of the resulting oxide layer was found to be strongly dependent on (a) the oxide layer existing prior to the selective oxidation, (b) the parameters of the treatment (i.e., composition and pressure of the furnace gases and time), and (c) the dose of aluminum implanted. Compositional analyses via ion backscattering and Auger electron sputter profiling were performed to study the processes and mechanisms.
Recent experience in the deposition of thick quartz films by rf magnetron sputtering
Authors: Mosely Roderick C. , Sans Claude A. , Campbell Sandra D. , Lamont Lawrence T.
Published: July 2002

Recent results demonstrating control of the step coverage profile by means of rf bias during rf magnetron deposition of thick quartz films are reported. The source and substrate power supplies are driven by a common oscillator, which permits the relative phase between source and substrate to be controlled. This adjustment has a profound influence upon the power required on the substrate table for a fixed bias. It is found that step coverage profile is primarily a function of substrate bias and only weakly dependent on substrate power.
The influence of discharge current on the intrinsic stress in Mo films deposited using cylindrical and planar magnetron sputtering sources
Authors: Thornton John A. , Hoffman D. W.
Published: July 2002

Previous work has shown that the transition pressure, pt, below which large compressive stresses are found in magnetron sputtered metal films deposited at low T/Tm, increases with the discharge current, at least for the case of cylindrical-post magnetrons with magnetic field configurations generated by magnets mounted within the cathode barrels. This paper reports measurements of the internal stress as a function of discharge current for Mo films deposited using a planar magnetron and also a cylindrical-post magnetron having an externally generated magnetic field which permitted the discharge voltage to be varied independent of the current. At each current, coatings were deposited over a sufficient pressure range to identify pt. Transition pressures, determined by stress, resistivity, and optical reflectance measurements, for both the planar and cylindrical magnetrons, exhibited an increase with discharge current, consistent with the previous work. Reducing the cylindrical magnetron magnetic field to increase the discharge voltage at a fixed current consistently yielded higher pt. Strong correlations were seen between pt and the discharge voltage for both the cylindrical and planar magnetrons. It is concluded that the increase in pt with discharge current is significantly influenced by the accompanying increase in discharge voltage and not associated with the concurrent increase in deposition rate per se.
Fermilab accumulator magnets vacuum chamber heating system
Authors: Satti J. A. , Lee G. N.
Published: July 2002

The Fermi National Accelerator Laboratory (Fermilab) is building an accumulator ring to store antiprotons for high energy physics proton–antiproton collisions in the Tevatron accelerator. The accumulator ring, approximately 474 m in circumference, consists of many quadrupole and dipole magnets connected with stainless steel vacuum chambers for beam circulation. The vacuum pressure required is in the low 10−10 Torr range. To reach this pressure, the vacuum chambers are baked at 300 °C each time they have been opened to atmospheric pressure. The critical problem is to bake the chambers in the magnets at high temperature without overheating the laminated magnets. Some of the magnets are 5 m long with very restrictive space for the heaters and insulation. An average space of only 7.5 mm around the chambers is available. In this space a heating system has been designed and tested to heat the chamber to 300 °C and allow a maximum temperature of 65 °C next to the magnet components. This was accomplished by using a heating blanket completely covered with a water cooled copper heat sink jacket to protect the magnet from the high temperatures. The design of a final selected heating blanket is discussed. A prototype test results are given with comparison of calculated and measured temperature distribution.
Target fabrication activities in Japan
Authors: Izawa Y. , Norimatsu T. , Yamanaka C.
Published: July 2002

Some of the recent achievements in fabrication technologies for laser fusion targets are reviewed. Fabrications of hollow glass and plastic microspheres, development of cryogenic targets, control of density and effective atomic number in coatings on microspheres, fabrication of complicated multishell target, and new characterization technique by electrostatic handling are described.
Changes in O2 and CO surface chemistry with increasing carbon concentration on W(100)
Authors: Jupiter P. J. , Viescas A. J. , Carbone C. , Lindau I. , Spicer W. E.
Published: July 2002

Photoemission electron spectroscopy employing He i radiation was used to study the adsorption of O2 and CO on W(100) and three carburized W(100) surfaces. The carburized surfaces exhibit LEED patterns of c(2×2), c(3×2), and (5×1) corresponding to 1/2, 2/3, and 1 monolayer of carbon, respectively. Upon carburization, emission is seen from C 2p states at −4.8 eV below Ef. Emission from W 5d states at −2.8 eV is broadened and shifted slightly to higher binding energy. Carbon concentration of only 1/2 ML is enough to show sufficient reduction in the tungsten −0.6 eV surface peak. A 1/2 L CO exposure to the carburized surfaces noticeably decreases emission from W 5d states at −2.8 eV but little change is seen in these states for the same CO exposure to W(100). CO adsorption is dissociative on W(100). CO initially adsorbs dissociatively on the 1/2 and 2/3 ML carburized surfaces but molecular adsorption begins after a sufficient number of W sites have been passivated by either C or O atoms from dissociated CO. At room temperature CO does not adsorb on the (5×1) surface. When cooled to 250 K, CO adsorbs molecularly on the (5×1) surface.
Growth and properties of single crystal TiN films deposited by reactive magnetron sputtering
Authors: Johansson B. O. , Sundgren J.-E. , Greene J. E. , Rockett A. , Barnett S. A.
Published: July 2002

Epitaxial stoichiometric (111)-oriented TiN films have been grown on cleaved MgO by dc reactive magnetron sputtering from pure Ti targets at substrate temperatures Ts ranging from 525–800 °C. The films were grown in mixed Ar/N2 discharges with the total sputtering pressure maintained constant at 3.5 mTorr (0.47 Pa). For Ts≲600 °C, N2 partial pressures PN2 that were either below or above a narrow range of values, which depended upon Ts, resulted in under- or over-stoichiometric films, respectively. However, at Ts≳600 °C, stoichiometric films could be obtained at any PN2, including pure N2, greater than a critical N2 partial pressure that varied from 0.2 to 0.4 mTorr (27 to 53 mPa) as Ts was increased from 600 to 800 °C. The Vickers hardness H, the room temperature resistivity ρ, and the temperature coefficient of resistivity TCR of stoichiometric TiN single crystals were found to be essentially independent of Ts and PN2. H was determined to be 2300±200 kg mm−2, about 15% higher than for bulk sintered TiN, ρ was 18 μΩ cm, and the TCR measured at temperatures between 100 and 400 K was 6200 K−1. The latter two results represent the lowest and highest values, respectively, yet reported for TiN films. The room temperature electron carrier concentration and mobility were determined from Hall measurements to be 5×1022 cm−3 and 6.7 cm2 V−1 s−1.
Correlation of quantitative Auger electron spectroscopy with secondary ion mass spectroscopic investigations of Al/Si/Cu VLSI metallization
Authors: Stevens H. A. , Hance R. L. , Hong C. , Pyle R. E.
Published: July 2002

Samples of sputter-deposited Al/Si/Cu very large scale integration (VLSI) metallization 1.4-μ thick having 1 wt. % Si and 0.0, 0.2, 0.4, and 0.8 wt. % Cu with and without a forming gas (N2/H2) 450 °C anneal for 1 h were analyzed quantitatively using Auger electron spectroscopy (AES) in a signal averaged depth profile mode. These data were correlated and compared with high resolution secondary ion mass spectroscopic (SIMS) depth profiles of the same samples. The purpose of these investigations was to study the feasibility of SIMS as a quantitative measure of Si and Cu concentrations in Al/Si/Cu VLSI metallization. In addition, these data were used to provide a preliminary description of the spatially averaged inhomogeneous distribution of Cu and Si in Al/Si/Cu metallization pre- and postanneal.
Selective patterning of single-crystal GaAs/Ge structures on Si substrates by molecular beam epitaxy
Authors: Sheldon P. , Dick J. R. , Hayes R. E.
Published: July 2002

Patterned single-crystal GaAs/Ge layers are grown on Si substrates by molecular beam epitaxy deposition through a bilayer mask. The ability to pattern device-quality GaAs structures on Si allows for integration of GaAs and Si devices on a monolithic chip. In this paper we describe the experimental details of a process that could be used to fabricate such circuits. The Si substrate, before growth, is patterned using a bilayer silicon nitride/silicon dioxide mask and conventional photolithographic techniques. During growth, in areas where the Si substrate is exposed, the GaAs/Ge layers grow epitaxially. After growth, a chemical etch is used that dissolves the mask, retaining the single-crystal GaAs/Ge pattern. The bilayer mask yields good pattern replication and prevents diffusion of Ga and As into the underlying Si devices, as shown by secondary ion mass spectroscopy data. The bilayer mask also aids in the lift-off process where thick GaAs/Ge layers are required and 100% lift-off yield is mandatory. Sample morphology and crystallinity are examined by scanning electron microscopy and reflection high-energy electron diffraction.
A review of thin film media for magnetic recording
Authors: Eltoukhy A. H.
Published: July 2002

Thin film materials and deposition techniques used for the manufacturing of high density magnetic recording disks are reviewed. Novel metal alloys and oxide thin films developed for high density horizontal and vertical recording technologies are listed, and their manufacturing processes are compared. Electroless and electrolytic plating, and sputter deposition techniques are briefly described with emphasis on the advantages and limitations of each technology. A discussion of research areas with potential for future developments in materials for storage applications is also presented.
Pumping of methane by St707 at low temperatures
Authors: Hobson J. P. , Chapman R.
Published: July 2002

A simple means of pumping small leak rates of methane is frequently required in long-term sealed-off devices such as evacuated solar absorbers. In this paper we examine, in this context, a chemisorption or catalytic pump the SAES getter St707. After suitable activation in an ultrahigh vacuum system a small sample of St707 (2.7×3 cm), with heater external to the vacuum system, was exposed to a methane leak as the sample temperature was raised in steps from room temperature to 400 °C, the highest temperature used. Pumping was first detected at 100 °C and at 400 °C the pumping speed was 2×10−3 l s−1 cm−2 (pumping area assumed 8 cm2), after 0.34 Torr l of methane had been pumped. Care was taken to distinguish these small pumping speeds from ionic pumping by the gages. The conclusion is that the St707 getter is suitable as a methane pump of low speed at low temperatures and pressures.
Monte Carlo analysis for the appropriate gauge location for an American Vacuum Society standard high vacuum pump speed measurement dome
Authors: Boeckmann M. D.
Published: July 2002

A Monte Carlo molecular flow simulation was performed on an AVS standard high vacuum pump dome to determine the appropriate location of a pressure gauge to measure the speed of a high vacuum pump. The location was chosen to match the molecular flux at the gauge with the molecular flux at the pump inlet. The resulting measured pumping speed will be equivalent to the pumping speed measured on an infinitely large dome, the so-called ‘‘intrinsic’’ pumping speed. Simulations were run on straight tubes and found to agree with available literature information. Simulations were run on an AVS standard high vacuum speed measurement dome to determine the appropriate gauge location as a function of pump capture coefficient, gas inlet tube geometry, and pressure gauge tubulation. The appropriate gate location for a 4 in. pump speed dome with a 3/8 in. o.d. tubing gas inlet tube 1 in. long after the inlet tube elbow is 1.05±0.03 R (90% confidence interval). The value was independent of pump capture coefficient, but a slight dependency on inlet tube geometry was found. The effect of gauge tubulation was also examined. Use of the results of the analysis in determining a ‘‘recommended practice’’ for pump speed measurement is mentioned.
Bonding and stability in narrow-gap ternary semiconductors for infrared applications
Authors: Wall A. , Caprile C. , Franciosi A. , Vaziri M. , Reifenberger R. , Furdyna J. K.
Published: July 2002

The electronic properties of narrow-gap ternary semimagnetic semiconductors Hg1−xFexSe and Hg1−xMnxSe have been studied using synchrotron radiation photoemission techniques. This work was undertaken to assess the character and stability of the Hg–chalcogenide bond. The results are compared to those of similar studies obtained for Hg1−xCdxTe and Hg1−xMnxTe alloys, and for the binary compounds HgSe and HgTe. Synchrotron radiation photoemission studies show that the addition of Mn or Fe to the binaries perturbs only slightly the Hg–chalcogenide bond, in contrast to the case of Cd where large destabilization is observed. A striking result of the present study is that the addition of Fe to HgSe greatly enhances the stability of the carrier concentration against standard processing techniques such as annealing in a Hg or Se atmosphere.
Metal–organic chemical vapor deposition hybrid substrates for HgCdTe
Authors: Schmit J. L.
Published: July 2002

This paper describes the process we used in selecting GaAs and InP as the best foreign (non-CdTe) substrates for metal–organic chemical vapor deposition (MOCVD) growth of CdTe to form hybrid substrates suitable for use as substrates for epitaxial growth of HgCdTe. We describe the MOCVD growth process and give typical characterization results. We carried out a 12 run statistical design experiment to identify the most important parameters which turned out to be the metal–organic pressures and the growth temperature. These hybrid substrates have been used for the growth of HgCdTe by liquid-phase epitaxy (LPE). Responsivity of 104 V/W is reported for Hg0.7Cd0.3Te with 3.5×1015 donors/cm3 grown on a long wavelength infrared (LWIR) transparent hybrid substrate.
Pulsed ion beam irradiation of Ni–Cr films on silicon
Authors: Fastow R. , Brener R. , Eizenberg M. , Brat T. , Mayer J. W.
Published: July 2002

Composite thin films, having compositions Ni25Cr75 and Ni75Cr25, deposited on single crystal silicon substrates were irradiated with a pulsed ion beam. These systems were compared to the binary Ni/Si and Cr/Si systems, and were characterized using Rutherford backscattering spectroscopy, Auger electron spectroscopy, x-ray diffraction, and transmission electron microscopy. Interfacial melting was observed in all samples. For the Cr/Si and alloy/Si samples, melting occurred at noneutectic interfacial compositions. The phase CrSi2, in a layered structure of nickel silicides (Ni2Si/NiSi/NiSi2), was present in the reacted layers. Auger electron spectroscopy showed that an enrichment of Ni (in the form of NiSi2) occurred at the silicon interface for both alloy compositions.
Unbalanced potential discharge characteristics for opposed-targets sputtering system
Authors: Matsuoka Morito , Hoshi Yoichi , Naoe Masahiko
Published: July 2002

In the opposed-targets sputtering system (OTSS), plasma is focused in the space between opposed targets by magnetic and electric fields. Usually, since an equal potential is applied to the targets, the discharge is in the balanced potential mode. In this study, unbalanced potential (UP) modes of discharge characteristics are investigated for the OTSS. Discharge characteristics strongly depend on the unbalanced voltage applied to the opposed targets. UP is seen to promote strong ionization just as the plasma confinement field and other discharge parameters do.
Unusual kinetics due to interface hydride formation in the hydriding of Pd/Mg sandwich layers
Authors: Krozer A. , Kasemo B.
Published: July 2002

The hydriding of thick Mg films with a 50–100 Å Pd film on top, as catalyst for H2 dissociation, was investigated by quartz-crystal microbalance uptake measurements in a combined UHV and high-pressure equipment. Unusual kinetics are observed: (i) the hydrogen uptake saturates far from MgH2 at room temperature and (ii) the saturation uptake decreases with increasing H2 pressure. The results are explained in terms of interface hydride formation at the Pd/Mg interface, which blocks hydrogen diffusion. A theoretical basis for this model is given by combining the dependence of hydrogen binding energy on local electron density, with the assumption that the lattice mismatch at the interface creates defect sites (e.g., vacancies) with low local electron density.
Free-carrier spin-induced Faraday rotation in HgCdTe and HgMnTe
Authors: Yuen S. Y. , Wolff P. A. , Becla P. , Nelson D.
Published: July 2002

We have observed free-carrier, spin-induced Faraday rotation in n-type HgCdTe and HgMnTe in the 10-μ region. The Verdet constant of the spin process is considerably larger than that of the interband or free-carrier plasma Faraday effects, and decreases as the light frequency is tuned away from the energy band gap.
Analysis of reactive sputtering mechanisms for NbN film deposition
Authors: Bhushan M.
Published: July 2002

A model for the reactive sputtering mechanism is discussed to assist in the selection of the optimum sputtering parameters for the deposition of NbN films with a high critical temperature Tc and low resistivity (at 20 K). The model is based on the assumption that the reaction between the target material and the reactive gas molecules takes place at the surface of the target. Optical emission spectroscopic studies of the plasma were conducted during the deposition of NbN films by reactive dc and rf magnetron sputtering in an Ar–N2 mixture. The substrates were not heated and the substrate temperatures were kept ≲100 °C during deposition. The intensity of a Nb emission line, which gives a measure of the sputtering rate, was monitored as a function of N2 pressure. The data were fitted to the model to select the optimum nitrogen pressure at different power densities and Ar pressures. The Tc of NbN films deposited at a high rate (>25 Å/s) by dc magnetron sputtering was ∼16 K. The highest Tc of films deposited by rf magnetron sputtering reached only ∼14 K due to higher levels of positive ion bombardment.
Properties of carbon coating films produced by electron cyclotron resonance plasmas
Authors: Minagawa H. , Hino T. , Yamashina T. , Amemiya H. , Ishibe Y. , Kato S. , Okazaki K. , Oyama H. , Sakamoto Y. , Yano K.
Published: July 2002

For carbon coating films produced by electron cyclotron resonance (ECR) plasma in ECR-2 (RIKEN), the depth composition profiles were analyzed by Auger electron spectroscopy (AES). In the AES analysis, the sputter-etching rate was two or more times lower than that produced by a radio frequency (rf) assisted glow discharge plasma in the TEXTOR tokamak. This result indicates that a hard or dense carbon film was produced by the ECR plasma. The hydrogen concentration of the film was determined by thermal desorption spectroscopy. The hydrogen content was approximately (20%–30%). The carbon films produced by the ECR plasma with different operation parameters were examined. The hydrogen concentration is increased when the gas pressure is increased. For the substrate biased negatively, impurities from the substrate were observed in the film. When the substrate was heated, no carbon film was formed.
Vacuum performance of the ultraviolet and x-ray rings at the National Synchrotron Light Source
Authors: Halama H. J. , Foerster C. L. , Kobari T.
Published: July 2002

The gas density and its composition expressed in partial pressures of various gases determine the lifetime of circulating current through bremsstrahlung and Coulomb scattering losses. The above quantities depend primarily on the gas desorption due to synchrotron radiation and on the installed pumping speed. During operation of the storage rings, the pressure decreases as the walls of the vacuum system are cleaned by synchrotron radiation. Since long lifetime is essential for good operation of all storage rings, accurate information on pressure around the ring should be available. Calibrated Bayard–Alpert gauges and residual gas analyzers have been installed in both rings. From their readings, average pressure and gas composition are evaluated and the beam lifetime calculated. In this paper we will present (a) National Synchrotron Light Source pressure measuring system, (b) time-dependent pressure and lifetime behavior, and (c) comparison of calculated lifetimes with measured lifetimes.
Evaluation of National Synchrotron Light Source beam line fast valve protection system
Authors: Foerster C. L. , Larson R.
Published: July 2002

A fast valve designed and produced at Brookhaven National Laboratory for the National Synchrotron Light Source (NSLS) was evaluated for operational and system parameters. A functional prototype of a typical beam line was built to measure fast valve protection for simulated experimental beam line catastrophic vacuum failures. The fast valve, which was designed to stop shock wave propagation due to in-rushing gas, yielded a nitrogen leak rate from 0.5 to 0.02 Torr l/s during the first 3 s of beam line vacuum failure. An UHV all-metal electropneumatic valve in series with the fast valve will close and seal in less than 3 s. The fast valve closure time which measured between 4.5 and 6.5 ms from initially sensing the shock wave to closure of the fast valve did not significantly change after vacuum bakeouts to 200 °C, repeated cycling, or shock wave operation. The fast valve firing circuit described sensed shock wave current from a miniature appendage ion pump and fired the fast valve in approximately 0.5 ms. Measurements were made for helium, nitrogen, argon, and air shock waves. Closing time and bounce were measured for several valves by sensing either laser or incandescant light during operation.
Growth and properties of radio frequency reactively sputtered titanium nitride thin films
Authors: Kumar N. , Pourrezaei K. , Fissel M. , Begley T. , Lee B. , Douglas E. C.
Published: July 2002

Polycrystalline thin films of titanium nitride with a resistivity in the range 20–25 μΩ cm have been consistently produced on water-cooled silicon wafers by using reactive sputtering of a titanium target in Ar/N2 mixture. The variations of resistivity and the deposition rate as the functions of N2 partial pressure and applied substrate bias voltage are investigated. The N2 partial pressure as a function of nitrogen flow rate is plotted for various radio frequency (rf) power levels. The TiN films have been characterized by a wide variety of analytical techniques, such as Rutherford backscattering (RBS), Auger electron spectroscopy (AES), x-ray diffraction (XRD), scanning electron microscopy (SEM), and four-point probe. These films are golden yellow in color. RBS shows these films to be stoichiometric and AES shows them to be free of any measurable oxygen. Two multilayer metallization systems (Si/TiN/Al and Si/Ti/TiN/Al) were built to test the effectiveness of these films as a diffusion barrier. Preliminary results show that TiN films are an effective diffusion barrier between Si and Al up to 600 °C for 10 min. These films have very good step coverage, and show acceptable contact resistance to silicon after 450 °C anneal in the Si/Ti/TiN/Al metallization system.
Crystalline and quasicrystalline phases formed by interdiffusion in evaporated Al–Mn thin films
Authors: Csanády Á. , Urban K. , Mayer J. , Barna P. B.
Published: July 2002

Bilayer and multilayer thin-film systems of Al–Mn were evaporated onto carbon foils prepared on Mo grids. The Al/Mn ratios were chosen to provide enough Mn for the second phase formation. Heat treatments were carried out in situ in a high-voltage electron microscope equipped with an ultrahigh vacuum specimen chamber. The appearance, growth, and transformation of the intermetallics were directly observed and studied by electron diffraction. Beside the crystalline phases the quasicrystalline i and T phases were also produced. The connection between the layer structures and the types of the intermetallics formed in the course of the heat treatments are shown.
Growth mechanisms of anodic oxide and sulfide films on HgCdTe
Authors: Strong R. L.
Published: July 2002

Three different markers were used to determine whether anodic films on HgCdTe were growing into the substrate and consuming the surface, or were depositing on top of the surface. All three experiments show conclusively that oxidation in KOH electrolyte occurs only by growth into the substrate. The two marker experiments applicable to oxidation in H2O2 and an experiment investigating the etching of Cd out of the oxide by H2O2 prove that for anodization in H2O2 there is growth both into the substrate as well as on top of the surface. One of the marker experiments indicates that the sulfide film also grows into the substrate.
Straightforward experimental evidence against the electron affinity rule
Authors: Niles D. W. , Tang Ming , Höchst H. , Margaritondo G.
Published: July 2002

Straightforward photoemission tests performed on the ZnSe–Ge and GaP–Si interfaces led to a breakdown of the electron affinity rule. The importance of this result and its impact on the theory of heterojunction band lineups is discussed.
Gas fueling with an axisymmetric magnetic divertor in the Tara tandem mirror
Authors: Post R. S. , Brau K. , Horne S. , Casey J. , Golovato S. , Sevillano E. , Shuy G. , Smith D. K.
Published: July 2002

An axisymmetric divertor has been installed at the central cell midplane of Tara to provide magnetohydrodynamics stability and to generate a high-density halo at the edge of the plasma. A dense halo aids sloshing ion buildup in the plug cells and increases shielding of the core plasma from charge exchange recombination. Separate gas fueling of the halo in the divertor allows for the different fueling requirements of the potential-confined core plasma and the flow-confined edge during plugged operation.
The surface chemistry of zinc dialkyldithiophosphate, an antiwear additive, on oxidized iron and steel foils
Authors: Rhodes Kent L. , Stair Peter C.
Published: July 2002

The chemisorption and thermal chemistry of zinc dialkyldithiophosphate (ZDP) were studied on iron oxide and AISI 52100 steel substrates using x-ray photoelectron spectroscopy (XPS). Solutions of alkyl and aryl ZDP’s in a synthetic hydrocarbon oil [poly-alpha-olefin (PAO)] were used. Surface oxide layers on both iron and steel foils were reduced to metallic iron when heated with a film of PAO on the surface. The addition of ZDP to the films prevented reduction. XPS revealed that a surface sulfate was reduced to sulfide upon heating. Several possible mechanisms for the surface antioxidant activity of ZDP are discussed. The results of this investigation suggest a new model for the antiwear activity of ZDP. ZDP prevents surface oxide reduction, maintaining an easily sheared surface layer, and thus preventing metal–metal contact and wear.
Properties of hard tungsten films prepared by sputtering
Authors: Shih K. K. , Smith D. A. , Crowe J. R.
Published: July 2002

The structure and properties of sputtered tungsten films up to 28 μm in thickness are reported. Hardnesses of more than 1700 kg/mm2 have been obtained for these films, this being several times the value of bulk tungsten. It has been found that hardness can be varied by changing the pressure, bias voltage, or power during sputtering. The hardness of these films is approximately constant with temperature up to 500 °C, in contrast to the hardness of bulk tungsten which decreases with temperature. Grain size has been estimated from the line broadening of x-ray diffraction peaks and by transmission electron microscopy. It has been found that hardness and grain size follow the Hall–Petch relationship.
Preparation of nitride films by Ar+-ion bombardment of metals in nitrogen atmosphere
Authors: Baba Y. , Sasaki T. A. , Takano I.
Published: July 2002

A preparation of thin nitride films on metal surfaces was presented. The nitrogenation was carried out by bombarding the metals with 8-keV Ar+ ions in nitrogen at 1.0×10−3 Pa. Among the 13 metals examined, the nitrides of nine metals were produced. The approximate thickness of the TiN film was ∼7 nm, which is comparable to the range of the Ar+ ion. The saturated values of the surface N/Me (Me:metal) are different among various metals examined, and are related to the chemical reactivity of the metal with nitrogen. The N/Ti ratio was inversely proportional to the Gibbs energy of nitride formation. These results suggest that the nitride was produced not only through the knock-on collision by the Ar+ ions but also through the thermochemical reaction at the nitrogen–metal interface, which is promoted by the ion bombardment.
Auger electron spectroscopy technique for nitrogen depth profiling in titanium compounds
Authors: Pantel R. , Levy D. , Nicolas D.
Published: July 2002

Although Auger electron spectroscopy is one of the most used techniques for surface and thin-film analysis, its application to TiN is very problematic. This is due to the overlapping of the principal nitrogen Auger transition (380 eV) with the Ti (383 eV) one. Therefore nitrogen detection in Ti compounds is very difficult. Generally an indirect nitrogen concentration evaluation is obtained using a ratio of two Auger peak amplitudes [‘‘Ti+N’’ (383 eV), Ti (418 eV)]. However this technique is inaccurate in alloys other than TiNx (ternary compounds or multilayers such as TiNxOy or TiNx/TiOy). In this paper we present a direct N detection based on the use of a secondary nitrogen Auger transition N KL1L2 (369 eV). Using a high-resolution cylindrical mirror analyzer this peak is separated from the Ti peaks. This simple procedure allows automatic depth profiling when combined with ion milling. We then present applications on Ti/Si and Ti/SiO2 structures rapidly annealed in N2 (650 °C, 100 s).
Modeling the effect of surface roughening on depth profiles. II. Polycrystalline metal
Authors: Tompkins Harland G. , Lytle Steve
Published: July 2002

Auger depth profiles of aluminum for thicknesses varying from ∼200 to 2000 Å are presented. The smearing of the inside interface is described using a previously developed algorithm where a sharp interface is assumed and a Gaussian convolution is applied. The width of the Gaussian is a function of the sputter depth and is composed of a constant part (associated with ion mixing) and a fractional part (associated with topographical roughening). In this work the fractional part was determined to be ∼20% of the sputtered depth for polycrystalline aluminum. In contrast, it was previously determined that for amorphous silicon dioxide, the fractional part was only ∼1.5%. This difference is attributed, at least in part, to the difference in sputter yield of grains and grain boundaries. For interdiffusion studies, it is essential that the instrumental technique effects be separated from the actual interdiffusional effects. The information presented herein should prove useful in intepreting such depth profiles.
Effect of hydrogen plasma treatment on CF4 plasma etching characteristics of single-crystal, polycrystalline, and amorphous silicon
Authors: Agrawal Neeta , Tarey R. D. , Chopra K. L.
Published: July 2002

A systematic study of etching rates in CF4 plasma of single-crystal, polycrystalline, and amorphous silicon exposed to hydrogen plasma has been carried out. An order of magnitude reduction in the etch rates after H2 plasma treatment has been observed in all cases and has been explained on the basis of an overlayer formation. Electron spectroscopy for chemical analysis and wet etching studies suggest the formation of a C, O, F, and H based complex overlayer, which reduces the CF4 plasma etch rate.
Quantitative determination of oxygen in AlGaAs layers by secondary ion mass spectrometry under 18O flux
Authors: Achtnich T. , Burri G. , Ilegems M.
Published: July 2002

Different experimental factors which influence the determination of oxygen content in Alx Ga1−x As semiconductor layers by secondary ion mass spectroscopy (SIMS) are described. The technique used involves flooding the sample surface with 18 O during profiling and corrects for errors due to oxygen adsorption on the sample surface during the analysis. Quantitative values for 16O content are obtained by comparison with implanted standards, taking into account corrections for changes in Al content and/or erosion rate. Simple tests allowing to check the analysis for charging effects and for internal consistency are illustrated. The results show that O concentrations down to the 4×1017 cm−3 level can be reliably determined.
Surface electronic behavior of actinide metals
Authors: Hao You Gong , Fernando Gayanath W. , Cooper Bernard R.
Published: July 2002

The self-consistent film linearized muffin-tin orbital method has been used to calculate the surface electronic structure of plutonium. This has been done using a (111)-oriented five-layer slab geometry. We believe this is the first self-consistent all-electron surface electronic structure calculation for an actinide system. We use the full potential in the interstitial and vacuum, while the non-muffin-tin (NMT) potential in the spheres is approximated by the extended interstitial NMT potential. The interest and difficulty of dealing with actinide electronic structure is associated with the large number of electrons in the atom, the importance of relativistic effects, and especially the behavior of the 5f electrons which typically are intermediate between itinerant and localized. The calculated work function of plutonium is strongly affected by the treatment of the 6p electrons, and with spin–orbit coupling effects included is 4.3 eV with 6p electrons treated as core, in good agreement with experimental values of 3.4 to 4.3 eV for uranium. A much higher calculated value of 8.4 eV, if the 6p electrons are treated as valence electrons, shows that the 6p electrons are largely localized. The narrow bandwidth of the 5f electrons and the position relative to s and d bands relate to the intermediate delocalization of the 5f electrons and the existence of hybridization with the s and d electrons.
Soft-x-ray appearance potential spectroscopy study of Pr2Fe14−xCoxB
Authors: Chourasia A. R. , Chopra D. R. , Malik S. K.
Published: July 2002

The praseodymium–iron–boron alloy, Pr2Fe14B, is found to possess excellent permanent-magnet properties. In this paper we report the investigation of the electronic structure of the system Pr2Fe14−x Cox B (x=0, 3, 5, 7, and 8.5) by soft x-ray appearance potential spectroscopy (SXAPS). SXAPS exploits the abrupt changes in the total x-ray emission associated with the thresholds for the excitations of core levels of the atoms in the surface region of the materials. This technique is particularly suitable for investigating the changes in the unoccupied states of rare-earth and transition-metal intermetallics which have high density of empty states at the Fermi level.The Pr M5 -level SXAPS peak in the system is found to exhibit negative chemical shift which progressively decreases as a function of Co concentration. However, the L2,3 levels of Fe and Co show increasing positive chemical shift. The chemical shifts data display a maximum at x=7 in these three cases which correlates well with reported behavior in the lattice constants of alloy systems. These chemical shifts have been discussed on the basis of charge transfer among the constituents of the system. The full width at half-maximum of the L3 peaks of Fe and Co indicates a decreasing trend as a function of Co concentration. These spectral characteristics have been interpreted in terms of the d-band narrowing as a result of interaction between 3d bands of Fe and Co.
Radical formation and surface reaction induced by laser radiation in the CH2I2–Al system
Authors: Mödl A. , Domen K. , Chuang T. J.
Published: July 2002

CH2 radicals and C2H4 molecules are produced and desorbed from an Al surface with a submonolayer coverage of CH2I2 when the adsorbed molecules are excited by 308-nm laser pulses. In contrast, laser-induced substrate heating by 532-nm pulses causes desorption of CH2I2 molecules and some thermal decomposition to form CH2I and I species. The results clearly illustrate the distinctive photochemical and thermal effects on a metal surface irradiated by lasers at different wavelengths.
Hydrogen isotope exchange via water exposure at oxyhydroxide surfaces of stainless steel and silicon
Authors: Gill J. T. , Watkins D. B. , Schultz J. A. , Anderson L. R. , Schmidt H. K. , Bastasz R. J.
Published: July 2002

The rates at which hydrogen isotopes are exchanged on oxyhydroxide surface films of 304L stainless steel and Si(100) upon exposure to water vapor have been investigated. Surface films were prepared by bombardment with D2O+. The surfaces were then monitored by secondary ion mass spectroscopy and direct recoil spectroscopy as a function of water (H2O or D2O) exposure. A fast and a second much slower process characterize the exchange at both films. The processes are isotopically reversable. The fast process is limited by water exposure, complete in 5–10 Langmuirs (L) for both materials, and is considered to involve terminal hydroxyl groups. The slow process appears to be the bulk diffusion-limited exchange within the oxyhydroxide film. Exchange-diffusion constants have been derived from fits to TRIM calculations for depth-of-origin of sputtered species: Dex ∼10−18 and 10−19 cm2/s for the films on 304L stainless steel (SS) and Si, respectively, at 295 K. Dex for 304L SS is consistent with previous results on FeOOH and SS. Diffusion exchange appears important in understanding tritium decontamination from surfaces.