bluuebunny/crossref_metadata_2025 huggingface dataset:
Solventless polyimide films by vapor deposition
Authors: Salem J. R. , Sequeda F. O. , Duran J. , Lee W. Y. , Yang R. M.
Published: July 2002

Vapor deposition polymerization (VDP) has been employed for the preparation of polyamic acid/imide films using a conventional thin film evaporator with a novel source design. The process utilizes the coevaporation of the dianhydride and diamine precursors. Control of source effusion rates permit film stoichiometry to be held to better than 1 mol %. Infrared, electron spectroscopy for chemical analysis (ESCA), and thermogravimetric analysis (TGA) results are consistent with the interpretation that the VDP films produced are polyamic acid curable to polyimide. The weight average molecular weight of the polyimide as determined by low angle light scattering (LALS) technique is 13 000, in agreement with the value estimated from the measured percent elongation at break point. Lift-off tests showed that vapor deposited polyimide is more resistant to hydrolitic attack at the silicon interface than spin coated Dupont RC5878. Dielectric constant (ε=2.91) and dissipation factor (tan δ=0.008) are lower than those reported for commercial materials. Index of refraction measurements show a lesser degree of anisotropy for VDP polyimide than spin coated films, which may be important in reducing interfacial stress. Finally, a complete dry process utilizing this VDP technique for the fabrication of submicron polyimide patterns was demonstrated.
Canadarm—a review of its flights
Authors: Sachdev S. S.
Published: July 2002

The Shuttle Remote Manipulator System (SRMS), or Canadarm, has been singularly successful in accomplishing both planned and unforeseen tasks in space. Following its first flight in November 1981, it has deployed payloads ranging in mass from 156 to 9765 kg. It has been flight tested for all its operating modes, its handling characteristics, and structural dynamics. It is now an operational subsystem of the Shuttle’s Orbiter. The SRMS was instrumental in the retrieval and repair of the Solar Maximum Mission Satellite (SMM) in 1984, and featured prominently in the salvage of the Palapa and Westar Satellites later that year. It has been used as an extension of the human arm in unforeseen duties such as removing ice from the orbiter’s waste management system and attempting to throw a switch on the malfunctioning Syncom Satellite. Most recently it has been part of an ingenious man/machine team in the in-orbit repair of the Syncom Satellite. A review of the highlights of the flight accomplishments of Canadarm is given.
Auger depth profiling studies with TiN films
Authors: Ristolainen E. O. , Molarius J. M. , Korhonen A. S. , Lindroos V. K.
Published: July 2002

Auger-depth profiling experiments of mechanically thinned samples were carried out with TiN films deposited on n-type (100)silicon wafers, stainless steel, and high-speed steel (HSS). The films were deposited between 700 and 800 K by triode ion plating based on the electron beam evaporation of titanium in an atmosphere containing both nitrogen and argon. All the films studied showed a Ti-rich interfacial layer and higher nitrogen concentration near the surface. An intermediate interfacial transition layer consisting of TiN, titanium, and silicon was found on the Si substrates. Interfacial layers of CrO2 and SiO2 were detected on stainless steel and vanadium carbides underneath the TiN coating remained after crater wear testing. Consequently, vanadium carbide and epitaxial growth of the TiN coating at these carbides is expected to be responsible for the remarkably good adhesion of TiN to HSS.
Characterization of β-SiC surfaces and the Au/SiC interface
Authors: Mizokawa Yusuke , Geib K. M. , Wilmsen C. W.
Published: July 2002

The chemistry of the β-SiC surface has been studied with Auger electron spectroscopy (AES) and x-ray photoemission spectroscopy (XPS). The chemically etched surface was found to be nearly stoichiometric, with only a small amount of adsorbed oxygen, which appears to be localized on the Si states. Ion sputtering caused the surface to become Si rich. Compared to Si, the β-SiC surface was very resistant to oxidation by air exposure at room temperature and when annealed in O2 at 300 °C. In addition, essentially no reaction occurred between Au and etched β-SiC even after extensive heat treatment.
Variable angle x-ray photoelectron spectroscopy and ion scattering spectroscopy study of the Ag/SiO2 interface
Authors: Pitts J. R. , Thomas T. M. , Czanderna A. W.
Published: July 2002

Thin Ag films of up to one monolayer on high purity fused silica have been investigated using variable angle x-ray photoelectron spectroscopy (XPS) and ion scattering spectroscopy (ISS). Silvered samples were prepared using the wet chemical process without reducers or by vacuum evaporation. After sensitization with a tin complex, it was determined from ISS that Sn is a surface species only and covers up to 30% of Si surface sites. Variable angle XPS verified these findings and suggested that the Sn is located above the Si surface plane. After silvering with the wet chemical process so that less than a monolayer of Ag is present on the surface, XPS showed that up to 60% of the surface Si is bound to Ag, while 20% of the surface Si sites remain covered by a Sn complex. ISS verified that Ag is a surface species and that 80% of the surface is covered by Ag and Sn. Variable angle XPS showed that Ag is raised out of the surface plane, and that it probably also resides over the Si. Analysis of one monolayer Ag films formed by vacuum evaporation on SiO2 show similar results. Using XPS peak positions and Auger parameter shifts, evidence was found for Ag–Si bonding. Variable angle ISS gave strong evidence of Ag residing over the Si.
Infrared absorption spectroscopy of pure and Cu doped CdTe
Authors: Bajaj J. , Shin S. H. , Newman P. R. , Huffman J. E. , Stapelbroek M. G.
Published: July 2002

Infrared absorption spectroscopy measurements have been made on Cu doped and nominally undoped CdTe at He temperatures and in the frequency range of 200–4000 cm−1. For Cu doped samples a well-resolved fine structure superimposed on a broad maximum, apparently related to Cu, is observed in the absorption spectrum between 1000–1500 cm−1 at 5 K. Several sets of sharp transitions are seen to recur regularly at an interval of 171 cm−1, corresponding to the LO phonon energy. Each set contains sharp lines separated by a constant energy of 30 cm−1, corresponding to TA phonon energy. The temperature dependence of the spectrum is consistent with multiphonon-assisted transitions. The intensity of lines at a given temperature scales almost linearly with the concentration of Cu in the sample. The sharpness of the lines suggests atomic transitions. Another interesting feature, apparently not related to the above sharp structure, is observed in some of the undoped samples in the far infrared range of 200–500 cm−1. In these samples, in addition to the intrinsic 2TO and 2LO phonon transitions observed in all samples, a new set of lines peaked at 357 and 380 cm−1 is observed. There is an indication that these new transitions are related to Cd vacancies in CdTe.
Thermal decomposition of lubricant oil adsorbed on gold and oxidized iron foils
Authors: Pan Fu-Ming , Stair Peter C.
Published: July 2002

The thermal decomposition of poly-α-olefin base lubricant oil (tridecene oligomer) adsorbed on clean gold and oxidized iron foils has been studied by x-ray photoelectron spectroscopy (XPS) and thermal desorption (TDS) in order to elucidate the chemical reactions associated with lubrication and wear. Thermal treatments were performed both in vacuum where the progress of reaction was monitored by XPS and TDS and in air with periodic examination of the surface by XPS. The coverage of oil was many monolayers on both surfaces at room temperature in vacuum. The intact poly-α-olefin desorbs at 130 °C with an activation energy of 70 kJ/mol which is equal to ΔH of vaporization. Thermal decomposition of the remaining adsorbed hydrocarbon occurs above 150 °C as indicated by the appearance of volatile hydrocarbon fragments and by shifts in the C(1s) binding energy. The temperature dependence of decomposition is identical on both substrates suggesting that it is not catalyzed by the surface. Under vacuum conditions the iron is reduced by surface reaction intermediates to produce carbon monoxide and metallic iron. This suggests that iron on the surface of bearings may cycle between oxidized and reduced states.
High-efficiency single-wafer sputter etching device
Authors: Wellerdieck K.
Published: July 2002

A small sputter etching device which achieves etch rates of more than 30 nm/min for thermal SiO2 on silicon is shown. The uniformity is ±5% on a 150-mm-diam wafer at an argon pressure of ∼0.5 Pa and a dc self-bias voltage below 600 V. This very low voltage and good uniformity at high etch rates are features of a newly designed magnetic field arrangement. The magnetic field is stationary with respect to the wafer. An influence of the magnetic field on the potential distribution in the rf diode arrangement was observed.
The effect of interaction range on the W(001) surface reconstruction phase transition
Authors: Roelofs Lyle D. , Wendelken J. F.
Published: July 2002

A model for the W(001) surface reconstruction phase transition is studied to elucidate the dependence of transition temperature on interaction range and other model parameters. We find that for the parameter set chosen extending the range of the interaction without changing the total reconstruction energy increases the model transition temperature somewhat. This reduces a previously reported discrepancy between the experimental transition temperature and that consistent with the calculated reconstruction energy, but only marginally.
Design and testing of a quartz friction vacuum gauge using a self-oscillating circuit
Authors: Hirata M. , Ono M. , Kokubun K. , Abe M. , Maruno N. , Shimizu K. , Ogawa T.
Published: July 2002

A quartz friction vacuum gauge (QF gauge) is based on the fact that the change in resonance impedance of a quartz oscillator is proportional to the frictional force of ambient gas. The QF gauge adopting a self-oscillating circuit has been developed in order to obtain quick response and high resolution. The sensor head is the tuning fork shaped (33 kHz) quartz oscillator, which is kept at about 50 °C by a temperature controller. The driving circuit consists of a phase shifter, a zero-cross detector, and analog switches connected to constant voltage suppliers, which send the quartz oscillator 200 mV peak-to-peak square-wave voltage. The I/V converter transforms the current through the quartz oscillator into the voltage. And the voltage is sent to the phase shifter and a meter driver. The testing results of the QF gauge are as follows. Measurable pressure range 10−1–105 Pa, pressure resolution 5×10−3 Pa at 10−1 Pa, stability 1.3×10−3 Pa, response time 0.2 s at the transition from 10−4 to 105 Pa.
Reflection electron microscope study of Pt(111) surfaces
Authors: Ogawa S. , Tanishiro Y. , Takayanagi K. , Yagi K.
Published: July 2002

Single-crystal spheres of Pt are cleaned by heating in situ in an ultrahigh vacuum electron microscope and (111) surfaces of the spheres are studied by reflection electron microscopy. Monolayer overgrowth of Au on the cleaned surfaces is observed. Image contrast of double-height steps as well as single-height steps is studied and the same contrast rules for the determination of sense of the steps as for steps on clean Si(111) surfaces are concluded. Motion of the steps due to sublimation by heating is observed.
Selective deposition of Ti: An interface study
Authors: Nender C. , Berg S. , Gelin B. , Stridh B.
Published: July 2002

If different substrates are bombarded by energetic (500–1000 eV) Ar ions during deposition of Ti, quite different film thicknesses may result on the substrates. In fact, on some of the substrates there will be no net deposition of Ti, while on others there will be formed a thin film of Ti. This is the bias sputtering selective deposition technique. The advantage with this technique is that the process is carried out in inert argon gas. Furthermore, almost any material may be selectively deposited. Since the substrate is bombarded by energetic argon ions during deposition its surface will be sputter etched. During the buildup of the Ti film a mixed interface may result. We have investigated the sharpness of these interfaces by Rutherford backscattering and by Auger depth profiling. We have found a critical processing interval where soft interfaces are formed by this technique. The experiments indicate that this ‘‘soft interface’’ interval appears when the deposition rate of sputtered Ti dominates only by a fraction over the bias sputter removal rate. However, if this processing interval is avoided, sharp interfaces may be obtained. In fact, the interfaces are as sharp as if Ti was sputtered onto the substrates without ion bombardment. However, the results found indicate that one has to compromise between interface sharpness and deposition selectivity. Results for Ti on Si, Pt, and Au will be presented.
An x-ray photoelectron spectroscopy/Auger electron spectroscopy study of titanium–palladium thin films on silicon(111)
Authors: Thomas J. H. , Hoffman D. M. , McGinn J. T. , Tams F. J.
Published: July 2002

Thin films of palladium (30 Å) on titanium (4–12 Å) were evaporated on silicon at 250 °C in a standard electron beam evaporator. Auger elemental depth profiling and angle resolved x-ray photoelectron spectroscopy show that titanium inverts position with the palladium layer in the deposit. The titanium-rich surface of the deposit consists mostly of titanium oxide. At the surface of the deposit, two components are observed in the Ti 2p spectrum: a high binding energy peak which is due to oxide and a low binding energy peak which is likely due to titanium silicides. Under the titanium-rich region, palladium, in its inverted position, forms a silicide as determined from the palladium 3d and silicon 2p core-level peak positions at the surface. The film configuration and existence of palladium silicide is confirmed by analytical transmission electron microscopy of cross sections of various titanium film thicknesses.
A high-resolution Auger electron spectroscopy study of the intergranular fracture of a temper-embrittled steel
Authors: Menyhard M. , McMahon C. J. , Yoshioka Y.
Published: July 2002

One of the earliest uses of Auger electron spectroscopy was the analysis of the intergranular fractures to determine how segregated impurities produce intergranular embrittlement. As spatial resolution improved it became evident that the impurities were inhomogeneously distributed among individual intergranular facets. Further improvement in the spatial resolution now with primary beam diameter down to 0.1 μm has revealed that impurity distribution even on individual intergranular facet can be highly nonuniform. In this study we report on a CrMoV steel steam turbine rotor embrittled by P segregation during 20 years of service revealing that the grain boundaries were mainly covered by two kinds of carbides: one Cr rich and the other Mo rich. The P level at the Cr rich carbides was generally lower than on the carbide-free regions.
Oxygen interaction with Pd3Sn: X-ray photoelectron spectroscopy and secondary ion mass spectrometry
Authors: Rotermund H. H. , Penka V. , De Louise L. A. , Brundle C. R.
Published: July 2002

We have studied the interaction of oxygen with Pd3Sn surfaces over the temperature range 25–800 °C and from coverages ranging from zero to saturation under ultrahigh vacuum (UHV) conditions. At high temperatures saturation corresponds to oxidation spreading over many atomic layers. Depth distribution information is obtained from x-ray photoelectron spectroscopy (XPS). Two altered states of Sn are identified from the XPS and x-ray induced Auger Sn and O chemical shifts. They are a nucleated oxide state and a ‘‘quasimetallic state.’’ A model is developed to describe the manner in which these are formed and their relative importance as a function of temperature and coverage. With this detailed XPS knowledge, it is then shown that static secondary ion mass spectrometry data do reveal much of the nature of the reaction once it is recognized that certain cluster ions are characteristic of particular products.
The nonlinearity of upper limiting pressure for quadrupole mass spectrometers
Authors: Hu Bingsen , Qiu Jiawen
Published: July 2002

This paper theoretically and experimentally discusses the factors restricting the upper limit of quadrupole mass spectrometers (QMS’s). It is shown that the causes of deviation from linearity of QMS’s at higher pressure (>10−4 Torr) can fall into two aspects: (1) the nonlinearity of the ionization process in the ion source and (2) the effect of ion–molecule collision scatter in quadrupole analyzers. Two ion sources for higher pressure operation have been designed. It has been shown that the model of the ion–molecule collision scatter used in the past is not valid for the quadrupole analyzer, and the maximum tolerable operating pressure of the quadrupole analyzer Pm is determined only by the length of the quadrupole rods system L. The pressure limit of the improved QMS for which L=80 mm has been extended to 1×10−3 Torr. This is in good agreement with the theoretical value.
The production of high-quality materials by special melting processes
Authors: Mitchell Alec
Published: July 2002

The three principal methods for aerospace engine alloy melting are vacuum induction melting, vacuum ore remelting, and electroslag remelting. These processes are now mature technologies with distinct limitations on producing defect-free materials. As the mechanical design of engines has advanced, particularly in respect of criteria related to fracture mechanics, these process limits have become critical in restricting advances in material performance. This paper outlines the defect types, their origins, and their relation to melting technologies. The solutions lie in the development of new melting methods, some of which are already being developed. These new methods show great promise in solving the present problems and could possibly supplant powder technologies as preferred routes for engine forging manufacture in the future. Most of the methods involve electron beam techniques which are now held to be acceptable and routine industrial practice. The vacuum induction melting system, vacuum arc remelting technique, and electroslag remelting processes will, however, continue to produce large quantities of alloys for less-demanding uses, while the new technologies will be used only for that small market fraction requiring the ultimate in alloy performance.
Protective coatings for radiation control in boiling water nuclear power reactors
Authors: Rao T. V. , Vook R. W. , Meyer W. , Wittwer C.
Published: July 2002

Stainless-steel surfaces (316 nuclear grade) develop 60Co-embedded oxide scales when exposed to a boiling water reactor (BWR) environment. Thin films such as Pd, Ni, Au, and Cr were found to drastically reduce the radioactive buildup. The films were prepared by vacuum evaporation and electroless deposition. The electroless coating consisted of a thin cathodically treated layer, followed by a nickel strike (∼1 μm) and an electroless layer (∼600 Å). The present paper describes the results obtained from a transmission electron microscope replica study of the radioactive growths that formed on uncoated and thin-film-coated stainless-steel rods. The coated rods, when exposed to a simulated BWR environment, exhibited corrosion film growths ranging from large faceted grains (uncoated) and isolated islands of similar crystallites (Au coated) to extremely small nucleated growths (Pd, Ni coated). Also, it was found that chromium oxide films, which generally form a protective oxide on stainless steel, do not completely stop either the corrosion film growth or the associated radioactive buildup. The morphologies of the corrosion film growth were correlated with the relative 60Co activity, and the substrate topography. The best coating to date was found to be a Pd thin film, 1000 Å thick, which reduced the radioactive buildup by a factor of ∼13.
A study of ion plating parameters, coating structure, and corrosion protection for aluminum coatings on uranium
Authors: Egert C. M. , Scott D. G.
Published: July 2002

A study of ion-plating parameters (primarily deposition rate and substrate bias voltage), coating structure, and the corrosion protection provided by aluminum coatings on uranium is presented. Ion plating at low temperatures yields a variety of aluminum coating structures on uranium. For example, aluminum coatings produced at high deposition rates and low substrate bias voltages are columnar with voids between columns, as expected for high-rate vapor deposition at low temperatures. On the other hand, low deposition rate and high bias voltage produce a modified coating with a dense, noncolumnar structure. These results are not in agreement with other studies that have found no relationship between deposition rate and coating structure in ion plating. This discrepancy is probably due to the high deposition rates used in these studies. An accelerated, water vapor corrosion test indicates that the columnar aluminum coatings provide some corrosion protection despite their porous nature; however, the dense noncolumnar coatings provide significantly greater protection. These results indicate that ion-plated aluminum coatings produced at low deposition rates and high substrate bias voltages creates dense coating structures that are most effective in protecting uranium from corrosion.
Structure and dynamics of periodic and randomly distributed surface features by high resolution helium atom scattering
Authors: Toennies J. Peter
Published: July 2002

The scattering of helium atoms from surfaces has recently been methodically improved so as to make feasible new, high resolution studies of surface structures and vibrations. Examples are presented on structural studies of Au(111) reconstruction which reveal structures with a lattice spacing of 64 Å and provide evidence for soliton domain walls. Other experiments on rare gas physisorbed layers show new buckling structures of the overlayers. Inelastic scattering from clean surfaces yields information on surface phonon dispersion curves, and this is illustrated by two recent studies of the Pt(111) and Si(111) 2×1 clean surfaces and of physisorbed rare gases on a Pt(111) surface. Other new experiments measure the size and structure of single defects (adsorbed molecules and steps) on an atomic scale from the observed interference patterns. Finally the use of helium atom scattering to detect low frequency adsorbate vibrations in the meV range is illustrated for chemisorbed CO molecules on Pt(111).
New data system for depth profiling of inhomogeneous samples by secondary ion mass spectrometry
Authors: Scholze Chr. , Frenzel H. , Maul J. L.
Published: July 2002

The Atomika secondary ion mass spectrometry (SIMS) Data System SDS 800 handles spatial resolved depth profiling at adequate spatial resolution at moderate data load. Optimization of dynamic range/detection limit and verification of the depth profile shape is provided without repeated runs. The efforts necessary to align structurized samples for analysis are reduced considerably.
Surface resonance effects in high- and low-energy electron diffraction patterns in molybdenite
Authors: Smith Andrew E. , Lynch D. F.
Published: July 2002

The high-energy electron diffraction surface analysis method of convergent beam reflection high-energy electron diffraction is compared with its low-energy counterpart current image diffraction. For the particular case of molybdenite it is demonstrated how a multislice diffraction computation scheme is able to faithfully reproduce experimental results for both techniques. The nature of surface resonance effects in the patterns is explored by means of this dynamical calculation. While many of the features can be explained by simple geometrical and Bragg’s law arguments, dynamical calculations are shown to be necessary for the detailed understanding of contrast distributions and their application to surface characterization.
Initial adsorption kinetics of oxygen on a Cu0.82Li0.18 alloy surface studied by combined Auger electron spectroscopy, x-ray photoelectron spectroscopy, and time-of-flight spectrometry of direct recoils
Authors: Mintz M. H. , Atzmony U. , Schultz J. A. , Shamir N.
Published: July 2002

The initial adsorption kinetics of oxygen on the surface of a polycrystalline Cu0.82Li0.12 alloy were studied at room temperature by combined Auger electron spectroscopy (AES) and time-of-flight spectrometry of direct recoils. The latter is structure sensitive, and in the case of copperlike structures, probes mostly oxygen residing on the ‘‘rough’’ planes [i.e., planes consisting of ridges and troughs such as the (110) plane], whereas oxygen located on the ‘‘smooth’’ planes [e.g., the (100)] is ‘‘invisible’’ to that technique. On the other hand, AES probes all surface oxygen atoms regardless of their structural arrangement. The combined measurements thus enable distinction between adsorption processes occurring simultaneously on different structural arrays (i.e., different types of planes) present on the polycrystalline surface. The following conclusions were derived: (i) Oxygen is preferentially adsorbed on the rough planes. (ii) The initial adsorption on the rough planes takes place on sites neighboring to substitutional Li atoms, leading to initial sticking probabilities higher than in the case of pure polycrystalline copper. (iii) Oxygen induced surface segregation of Li occurs at room temperature. This ‘‘segregation’’ is actually an exchange between topmost Cu atoms and Li atoms in the second layer beneath the surface. (iv) Oxygen adsorbed on the rough planes migrates to the smooth planes (a ‘‘spillover’’ effect) leading to enhanced effective ‘‘sticking probabilities’’ on these planes.
Characterization of the surface oxidation and magnetic properties of MnFe thin films
Authors: Cohen S. L. , Russak M. A. , Baker J. M. , McGuire T. R. , Scilla G. J. , Rossnagel S. M.
Published: July 2002

There is considerable interest in understanding the surface oxidation reactions of transition-metal alloys with potentially useful magnetic properties. These reactions can either lead to passivation or corrosion of the magnetic film under normal atmospheric conditions. Little is known, however, about the surface oxidation reactions of MnFe. In the present study, thin films of MnFe prepared by dc magnetron sputter deposition onto Si, Cu, and Ni80Fe20 have been characterized magnetically by superconducting quantum interference device (SQUID) and vibrating sample magnetometer measurements and their surface chemistry has been followed by angle resolved x-ray photoelectron spectroscopy and ellipsometry. The reactivity of the clean MnFe surface with O2, H2O, and N2 was investigated. The interaction of MnFe with O2 proceeds by preferential oxidation and surface segregation of Mn oxide. The final products of oxidation after a 66 000-L exposure are MnO and Fe2O3, in agreement with thermodynamic considerations. Compared to the reactivity of O2 with MnFe, the adsorption of H2O on MnFe is extremely sluggish, while N2 does not adsorb at all. The controlled oxidation behavior of MnFe is compared and contrasted to that observed for the related alloy NiFe and to that observed in air oxidation of both these alloys.
Hyperthermal gas–surface scattering
Authors: Weiss P. S. , Amirav A. , Trevor P. L. , Cardillo M. J.
Published: July 2002

We summarize our recent results of scattering hyperthermal (1–15 eV) rare-gas atoms from single-crystal semiconductors. These include collisional excitation of carriers in the semiconductor, the ejection of charged and neutral surface particles, and the projectile scattering distributions characteristic of the strongly inelastic collisions. The dependence of the electronic excitation of the semiconductor upon the incident energy, angle, and atom are consistent with the creation of a local thermal hot spot with which there is fast electronic equilibration. In contrast, for the ejection of ions from the surface, the incident and ejected particle energy and angle distributions suggest direct, large momentum-transfer processes. The scattered rare-gas atom distributions exhibit large energy loss, yet are strongly structured and surprisingly sensitive to surface topography.
Reactively sputtered TeOx thin films for optical recording systems
Authors: Di Giulio M. , Micocci G. , Rella R. , Tepore A.
Published: July 2002

Tellurium suboxide (TeOx ) thin films have been obtained by rf reactive sputtering deposition by using a Te target and an Ar–O2 gas mixture. Different samples were prepared by changing both the rf power (80–200 W) and the oxygen concentration in the sputtering gas. The transmissivity and the reflectivity of these films change markedly by thermal treatment at critical temperatures in the range 120–150 °C. This property makes these films suitable for optical disk recording with a low-output power laser diode.
Auger electron spectroscopy analysis of the role of oxygen in the frictional behavior of steel lubricated with poly-α-olefin
Authors: Dugger M. T. , Chung Y. W. , Cheng H. S.
Published: July 2002

Despite the fact that the major component of any lubricant package is the base oil, its reaction with the environment and substrate and the effect on the frictional behavior of the contact are not well understood. The present work was accomplished in a custom ultrahigh vacuum chamber that permits measurement of the friction coefficient during a ball-on-disk test and in situ Auger electron spectroscopy (AES) of disk surfaces tested under vacuum conditions. Results for 52100 steel lubricated with poly-α-olefin (synthetic base oil) show a more rapid decrease in contact life (distance slid to failure) with increasing load in vacuum than in air. Vacuum tests at an average Hertzian pressure of 550 MPa exhibited essentially zero life while tests in air at the same load survived 10 km of sliding. Preliminary AES results indicate that maintenance of a thick oxide is connected with extended contact life.
Influence of impurity gases on properties of Co–Cr sputtered films
Authors: Sagoi Masayuki , Nishikawa Reiji
Published: July 2002

The influence of impurity gases on c-axis orientation for Co–Cr sputtered films was investigated, using x-ray diffraction analysis. The O2 partial pressure at which c-axis orientation begins to decline depends on the Cr content of films. C-axis orientation for higher Cr content films was not disturbed up to higher O2 partial pressure. Cr plays an important role in protecting films from oxidation during deposition. For c-axis orientation, N2 had equal influence on different Cr content films, and was more detrimental than O2. Reduction in c-axis orientation corresponded well to an increase in spacing of c planes with impurity gas addition and was, therefore, attributed to the entrapment of impurity gas into the film. This hypothesis was confirmed in the case of oxygen with Auger microscopy. O2 addition was considered to be advantageous because it suppresses grain growth without damaging c-axis orientation. Increase in saturation magnetization was observed only for higher Cr content films with O2 addition; although actual composition of the films was almost equal to that of the targets. Perpendicular coercivity and anisotropy fields of higher Cr content films decreased, even without reduction in c-axis orientation, with increased O2 addition.
Formation of the Ca/GaAs(110) interface
Authors: Mao D. , Young K. , Stiles K. , Kahn A.
Published: July 2002

The morphology, chemistry, and band bending at the Ca/GaAs(110) interface are studied with Auger electron spectroscopy, electron energy-loss spectroscopy, low-energy electron diffraction, x-ray photoemission spectroscopy, and ultraviolet photoemission spectroscopy. Ca is found to grow nearly uniformly on GaAs at RT. There is a Ca–Ga exchange reaction at the interface. An intermediate position of the Fermi level (EF) resulting from the formation of adsorbate induced states and native defects is found at low coverage at 0.75–0.9 eV above the top of the valence-band maximum (VBM). An additional shift of EF leading to a final position 0.55 eV above VBM takes place when metallicity develops in the overlayer. The results for this interface support Schottky barrier models based on gap states induced or modified by the metal.
Ion assisted deposition of oxynitrides of aluminum and silicon
Authors: Al-Jumaily G. A. , Mooney T. A. , Spurgeon W. A. , Dauplaise H. M.
Published: July 2002

Optical thin films of nitrides, oxynitrides, and oxides of aluminum and silicon were deposited using ion assisted deposition. Coatings were deposited by evaporation of either AlN or Si with simultaneous bombardment with 300-eV ions of nitrogen, oxygen, or a mixture of oxygen and nitrogen. The chemical composition of the coatings was varied by varying the gas mixture in the ion beam, making it possible to vary the index of refraction of the coatings during deposition from 1.44 to 2.1 in the case of silicon oxynitrides, and 1.62 to 2.1 in the case of aluminum oxynitrides. Optical properties and environmental stability of the coatings were examined. Coatings are stable under severe conditions of humidity and temperature.
Interface analysis of monolayer and solution cast films of a polymerizable functionalized diacetylene (B1P51)
Authors: Hook Kevin J. , Gardella Joseph A.
Published: July 2002

The process of ion formation in static secondary ion mass spectrometry from functionalized polymer surfaces has been investigated using a polymerizable Langmuir–Blodgett film as a model system. In this study the variation in signal intensity of charge stabilized positive ions from the polymerizable quaternary amine amide diacetylene compound (B1P51) are used to monitor the process of polymerization, substrate chemistry (Au, Ag, and Ge film substrate), and variation due to film deposition method (i.e., Langmuir–Blodgett, solution cast). Each affects the type of film surface formed. Coverage, film thickness, homogeneity, and molecular structure and composition are obtained from x-ray photoelectron [XPS or electron spectroscopy for chemical analysis (ESCA)] and Fourier transform infrared (FTIR) spectroscopy measurements. Comparisons between ESCA and FTIR analyses have been used to determine the polymerization mechanism of the diacetylene. Correlations between changes in the ESCA N 1s core electron region and changes in the secondary ion yields are discussed.
Interstitial total energies and diffusion barriers in Hg1−xCdxTe
Authors: Morgan-Pond C. G. , Schick J. T. , Goettig S.
Published: July 2002

The previous simple model used to calculate energy trends for the deep levels due to localized electronic states associated with interstitial and substitutional defects has been extended to obtain estimates of the total energy for interstitials at different sites in the lattice. These calculations have been applied to predict the preferred tetrahedral site for Hg, Cd, In, and Te interstitials in Hg1−xCdxTe, and to investigate a possible diffusion path for these interstitials.
Dislocations in Hg1−xCdxTe/Al2O3(sapphire) grown by metalorganic chemical vapor deposition
Authors: Maruyama Kenji , Shinohara Koji
Published: July 2002

Causes of the dislocations in Hg0.83Cd0.17Te layers on (0001) sapphire substrates grown by metalorganic chemical vapor deposition (MOCVD) have been clarified by dislocation etch pit technique. Dislocations near the interface are the misfit dislocations caused by the interdiffusion. Dislocations near the surface are the dislocations penetrating the epilayers from the CdTe buffer layers. The dislocations similarly behave in both MOCVD-grown HgCdTe and liquid phase epitaxy grown HgCdTe.
Impurity doping of HgTe–CdTe superlattices during growth by molecular-beam epitaxy
Authors: Wroge M. L. , Peterman D. J. , Feldman B. J. , Morris B. J. , Leopold D. J. , Broerman J. G.
Published: July 2002

We demonstrate the use of In and Ag as n- and p-type dopants, respectively, to controllably dope (100)-oriented HgTe–CdTe superlattices during molecular-beam epitaxial (MBE) growth. When normalized by the superlattice growth rate, the low-temperature Hall-carrier concentrations of both In- and Ag-doped superlattices are shown to have an exponential dependence on the respective effusion-cell temperatures in the electron and hole concentration ranges of ∼1016 to 1018 cm−3 . The upper limit on the diffusion coefficient for In at the low MBE growth temperature of ∼160 °C is determined to be 5×10−15 cm2 /s by use of secondary-ion mass spectrometry. Hall-effect and current–voltage measurements verify that the combination of In and Ag doping allows the formation of p–n electrical junctions. These results provide the first evidence of p–n junction formation in a HgTe–CdTe superlattice.
Evaluation by room-temperature electroreflectance of the 77 K dark-storage time of bulk mercury cadmium telluride measured on metal-insulator semiconductor devices
Authors: Raccah Paul M. , Garland James W. , Yang De , Abad Hisham , Strong Roger L. , McNeill Matthew C.
Published: July 2002

We have studied a set of 14 very carefully characterized samples by spectroscopic ellipsometry, electrolyte electroreflectance (EER), and other measurements, and have measured the 77 K storage time τ of metal-insulator semiconductor (MIS) devices built on these samples. The measured storage times ranged from 6.8 to 130.8 μs. Only the results of the EER measurements showed a correlation with the measured values of τ. We interpret our EER results in terms of a two-phase model consisting of bulk plus very thin, highly defectuous regions, possibly associated with subgrain boundaries. The observed correlation between the values of the incremental linewidth ΔΓ of the thin defectuous regions and the values of the charge-storage lifetimes τ of the MIS devices is excellent and capable of predicting the values of τ. Furthermore, the exact form of the observed correlation is shown to follow immediately from a simple physical model. Correlations between the values of τ and those of other parameters measured by EER were also observed. They suggest a possible simple physical picture for the primary origin of dark current in these devices. This is the first predictive quantitative correlation ever observed between the results of room-temperature optical characterizations of semiconductor materials and the low-temperature electrical performance of devices built on those materials.
Mechanisms of component diffusion in mercury cadmium telluride
Authors: Tang Mei-Fan Sung , Stevenson David A.
Published: July 2002

The component diffusion coefficients for the Hg0.8Cd0.2Te (MCT) system are measured using radioactive tracers. Multiple branches are observed in the tracer diffusion profiles which are related to fast and slow-diffusing components. Diffusion models for each component are proposed based on the defect chemistry of MCT, a calculation of the thermodynamic factor, and the relationship between component diffusion coefficients and the interdiffusion coefficients for pseudobinary systems. The model provides insight into the thermodynamic properties of the system, the mechanisms for diffusion, and the practical application of tracer diffusion data to interdiffusion and p-to-n conversion by Hg annealing.
Ar and excess N incorporation in epitaxial TiN films grown by reactive bias sputtering in mixed Ar/N2 and pure N2 discharges
Authors: Hultman L. , Sundgren J.-E. , Markert L. C. , Greene J. E.
Published: July 2002

Epitaxial TiN films were grown on (100), (110), and (111) oriented MgO by reactive magnetron sputtering from a Ti target in both mixed Ar/N2 and pure N2 discharges. An applied negative substrate bias Vs (0≤Vs≤600 V) was used to vary the flux and energy of impinging Ar+ and/or N+2 ions. The film microstructure was analyzed by transmission electron microscopy and electron channeling and the relative concentration CAr of trapped Ar was measured by energy-dispersive x-ray analysis. For a given value of Vs, CAr initially increased with increasing substrate temperature Ts above the epitaxial temperature Te∼550 °C due to more efficient Ar channeling as the crystals became better ordered. However, CAr reached a maximum for all film orientations at Ts∼750 °C and decreased at higher Ts due to Ar loss by segregation to the surface and desorption. At a given Ts and Vs, CAr increased with the channel width in the order: (110)>(100)>(111). Gas bubbles formed in films deposited at 550≤Ts<800 °C and 400≤Vs≤600 V due to precipitation from a supersaturation of implanted Ar and/or N. The most stable shape for pure N2 bubbles was observed to be a {100} cube with {110} and, to a lesser extent, {111} facets indicative of anisotropy in TiN surface energies γ with γ100<γ110<γ111. The spacing of moiré fringes observed in transmission electron micrographs indicated that in at least some N2 bubbles, nitrogen was present in the face-centered-cubic solid phase.
Thin-film deposition in ultraclean environments
Authors: Lewis K. L. , Muirhead I. T. , Pitt A. M. , Cullis A. G. , Williams G. M. , Wyatt-Davies T. J.
Published: July 2002

Significant improvements can be made in the fabrication of optical thin-film structures by using molecular-beam and ultrahigh vacuum techniques. These lead to the achievement of more stable films and multilayer coatings, with improved morphology, density, and resistance to laser induced damage. A wide range of materials can be produced, from simple binary materials to more complex multicomponent materials such as ternary rare-earth chalcogenides and perovskite phase high-Tc superconductors. The microstructure of the film can be controlled to a high degree by using quasisuperlattice techniques, which also provide a means of refractive index synthesis. This can be applied to simple graded structures or to complex periodic gradings as required for Bragg-like structures. Etalon filters fabricated using the technique have been used for optical bistability experiments and have exhibited stable operation for periods of many hours, under continuous cycling.
Imaging polished sapphire with atomic force microscopy
Authors: Barrett R. C. , Quate C. F.
Published: July 2002

The polished faces of c- and r-oriented single-crystal sapphire have been studied with an optical deflection-sensed atomic force microscope using microfabricated cantilevers and a fiber optic-based light source. Images taken with repulsive contact forces reveal equally spaced atomic steps. The spacing between these steps corresponds with the off-axis angle of polishing (∼10 arc-min). An unidentified large-scale periodicity (∼1 micron) is also observed. Attractive-mode images of the same sample have been obtained using electrostatic forces. This was accomplished by evaporating a thin metal film on the sample side of the cantilever. Charge is deposited on the sample by applying a bias to an electrode attached to the back side of the sample and allowing it to come to equilibrium. These attractive-mode images reveal the same large-scale periodicity as with repulsive mode, but with an increased amplitude. This result implies that the features are more than simple topography, and possibly correspond to regions of charge accumulation.
X-ray photoelectron and mass spectroscopic study of electron irradiation and thermal stability of polytetrafluoroethylene
Authors: Wheeler Donald R. , Pepper Stephen V.
Published: July 2002

Polytetrafluoroethylene (PTFE) was subjected to 3 keV electron bombardment and then heated in vacuum to 300 °C. The behavior of the material as a function of radiation dose and temperature was studied by x-ray photoelectron spectroscopy (XPS) of the surface and mass spectroscopy of the species evolved. A quantitative comparison of the radiation dose rate with that in other reported studies showed that, for a given total dose, the damage observed by XPS is greater for higher dose rates. Lightly damaged material heated to 300 °C evolved saturated fluorocarbon species, whereas unsaturated fluorocarbon species evolved from heavily damaged material. After heating the heavily damaged material, those features in the XPS that were associated with damage diminished, giving the appearance that the radiation damage annealed. The observations were interpreted by incorporating mass transport of severed chain fragments and thermal decomposition of severely damaged material into the branched and cross-linked network model of irradiated PTFE. The apparent annealing of the radiation damage was due to covering of the network by saturated fragments that easily diffused through the decomposed material to the surface region upon heating.
Surface analysis of the adhesive bond between various Cu, Sn, and Fe bronze alloys and rubber
Authors: Stout D. A. , Rife R. J.
Published: July 2002

Auger electron spectroscopy (AES) was used to characterize laboratory produced bronze plated steel sheets and AES and x-ray photoelectron spectroscopy (XPS) were used to investigate the interphase layer between these sheets and rubber. These sheets were produced to simulate bronze coated steel wire used in tire beads. The AES analysis showed that different bead wire production conditions could be reproduced in the laboratory. The bronze–rubber interface was prepared for investigation by peeling the steel sheet from the rubber and also by depth profiling to the interface through the steel sheet which had been electrochemically thinned to a thickness of <1 μm. The Cu was found to have formed a copper sulfide layer on top of a copper oxide layer. Layers of Sn, Fe, and Zn (from the rubber) were observed in the adhesive layer.
Comparison of ion-implantation-induced damage in narrow-gap (0.1 eV) Hg1−xCdxTe and Hg1−xZnxTe
Authors: Uzan-Saguy C. , Richter V. , Shaanan M. , Kalish R. , Triboulet R.
Published: July 2002

The buildup of damage caused by In ion implantation (320 keV, 1012–1015 cm−2) in Hg1−xCdxTe (x=0.24) (MCT) and Hg1−xZnxTe (x=0.16) (MZT) is studied by means of Rutherford backscattering spectroscopy (RBS) channeling along the <111≳ and <100≳ directions using 320 keV protons. The channeled proton RBS spectra, which for room-temperature implantations always exhibit dechanneling, are analyzed by using Quérè’s theory to yield the amount of damage and its depth profile for each case studied. Although the general trend of the damage buildup in Hg1−xZnxTe resembles that of Hg1−xCdxTe the Zn-containing compound consistently damages more than its Cd-containing counterpart for a given dose. This observation can be accounted for by the different energy density deposited by the implant in each case, which in turn is related to the different percentage of HgTe in the two crystals and by the enhanced defect recombination in MCT. It is also found that both Hg1−xZnxTe and Hg1−xCdxTe damage more easily along the <111≳ as compared to the <100≳ crystallographic direction. This fact can be explained by the influence of the <111≳ preferentially oriented dislocations on the dechanneling of the probing beam. These results may have implications for the use of MCT (x=0.24) and MZT (x=0.16) as materials for infrared detectors operating in the 10 μm range.
Energy-resolved angular distributions of O+ ions at the radio-frequency-powered electrode in reactive ion etching
Authors: Janes Joachim , Huth Christoph
Published: July 2002

Mass-selected distributions of bombardment energies of O+ ions at the powered electrode of a reactive ion etcher are investigated under angles between ±10° with respect to the electrode normal. The energy distributions consist of split high-energy peaks and continuous intensities between 50 eV and the maximal energy defined by the potential drop across the sheath. Ions found in the bimodal split high-energy peaks show angular distributions with widths between 2° and 6° [full width at half-maximum (FWHM)]. The continuous part of the ion energy distributions exhibit angular widths between 7° and 11° (FWHM). The observed phenomena in the ion energy and ion angular distributions are interpreted as combined effects of elastic scattering and dissociative collisions in the sheath.