bluuebunny/crossref_metadata_2025 huggingface dataset:
Ferroelectric Properties of Tri-glycine Sulphate Thin Films
Authors: Jacobs J. T. , Keester K. L.
Published: July 2002

Thin film of TGS between 1300 Å and 1.6 μ have been deposited by a spinning technique on A1Mg discs at low temperatures. The crystalline texture is radially spherulitic with the c-axes being confined in the plane of the substrate. The ferroelectric hysteresis curves show a maximum saturation polarization Ps of 2μC/cm2 at 60 Hz and a coercive voltage of 1.8 V. The Curie temperature of the films with metal electrodes was 51±1 °C and the small signal relative dielectric constant was 35. The S-curves show that a 10-V pulse of 10 μsec duration can switch 100% of the 60-Hz polarization. The retention was measured for times up to one second, and appeared to be relatively constant at that time interval and beyond. The built-in bias associated with the work function of the top electrode was observed by C-V measurements.
Scattering of Metastable Molecules from a Gas-Covered (100) Surface of Germanium
Authors: Craig J. H. , Dickinson J. T.
Published: July 2002

Studies have been made of the scattering and deexcitation of thermal energy beams of metastable Ar, He, Ne, and N2 from an oxygen-covered germanium surface. It has been found that the survival of incident metastable species after a surface collision is strongly dependent on the degree of surface gas coverage. Using the metastable time-of-flight technique, both angular scattering and time-of-flight distributions were measured for the scattered metastable species. Changes in the TOF distribution of the scattered molecules relative to the incident distribution have been observed. In addition, changes in angular distribution as well as total metastable survival have been observed as a function of incident angle. Differences in survival for the various species studied have been measured and are discussed in terms of the excitation energy of the excited electron in the metastable atom relative to unfilled energy states at the germanium surface.
A Fast Turn Around Electron-Beam Pattern Generation System
Authors: Piwczyk B. P. , McQuhae K. G.
Published: July 2002

An electron-beam mask-generation system designed to demonstrate fast turn around and high resolution capability is described. The system has been developed using an Advanced Metals Research 900 SEM and a Nuclear Data 812 computer. Patterns are generated utilizing a matrix of 4096×4096 randomly addressable data points. Complex and/or large patterns can be generated by mechanical repositioning of the substrate and scanning of adjacent fields. A complete stepped and repeated master plate is produced in several hours as compared with several days using conventional systems. The time saving has been primarily achieved by combining the artwork generation, reduction, and step and repeat operations into a single operation. Compatibiltiy with conventional computer aided design and graphics software has been maintained by translating ordinary artwork generation data into information acceptable by the electron-beam system. Extensive software allows virtually all geometries to be generated by the system.
Integrated Circuit Production with Electron Beams
Authors: Livesay W. R.
Published: July 2002

The merits of two electron-beam systems are discussed, one for mask generation and the other for wafer alignment and exposure. The performance characteristics of both systems are described, including problems involved with IC fabrication. Results of resolution, distortion, and alignment studies are given on both systems. The single-beam mask generator employs a field-emission source, and the performance advantages and disadvantages of this source for microfabrication are detailed. The field-emission source is imaged by an electrostatic lens at a 10-cm working distance. The characteristics of the focusing and deflection system are given. Parameters such as writing speed, beam current, resolution, and area of coverage are compared to conventional electron sources and performance results are reported. The performance of both cold and thermal field-emitters is also discussed. The electron projection system which utilizes a noble-metal patterned photocathode electron source is described. Electron-optical characteristics of the projection system are discussed, including results of alignment and distortion tests. The research model as well as the fully automated electron-projection system designed to process up to 100 wafers per hour are described.
The Fabrication of IGFETS using Electron-Beam Technology
Authors: Pickar K. A. , Thibault L. R.
Published: July 2002

We study here the fabrication of p-channel MOS field effect transistors with 4 μ gate lengths, made with electron-beam lithography substituted for conventional photolithography. The remainder of the processing included tungsten metallization with self-aligned ion implanted source and drain regions as described by Moline et al., and by Boll and Lynch (IEDM, 1972). The resulting transistors were characterized by turn-on voltage, Vt of 1.3–1.6 V (〈0100〉 orientation) and 1.8–2.1 V 〈111〉. For the 〈100〉 devices, the distribution in Vt across each slice was very tight (2σ < 0.1 V). The experimental values for Vt could be predicted from independently measured values of substrate doping and flatband voltage. Transconductance per square of gate was typically ∼ 14 ± 1.4 μʊ(i.e., μΩ−1) (at VG–Vt=−3V) for devices with a gate oxide thickness of 1000 Å and a gate width of 200 μ. The value for mobility, μ, for the 〈100〉 devices was estimated to be 160 cm2 V−1 sec−1. The punch-through voltage was 23 ± 1.5V. The bias-temperature stability of the resulting devices was found to be strongly dependent on the crystal orientation. Slices with 〈100〉 faces were highly stable (<0.08 V shift after five minutes of positive or negative application of 106 V/cm at 300 °C); slices with 〈111〉 orientation were considerably less stable (up to 0.7V shift under the same conditions). The results are in general accord with previous results using conventional photolithography projected to account for narrower gate lengths. They indicate that no additional complications were introduced by the substitution of electron-beam lithography.
Computer-Aided Design and Experimental Investigation of an Electron–Optical Collimating Lens
Authors: Wang C. C. T. , Harte K. J. , Curland N. , Likuski R. K. , Dougherty E. C.
Published: July 2002

An electron–optical system capable of producing a highly collimated, large-diameter beam was designed, built and tested. The system consisted of a strong, decelerating condenser lens followed by an accelerating, collimating, “Kan” lens. The lenses were designed with the help of a large digital computer, using a combination of relaxation and analytical techniques. The Kan lens, which was the critical component, had a parabolic potential on a cylindrical boundary and terminated in an endplate containing an array of small exit holes. System performance was investigated by ray-tracing techniques; over-all angular accuracy was 0.005 mrad. Several systems were built, with an insulated-ring construction method, and tested by both a Moiré pattern technique and an extended column method, the latter accurate to 0.05 mrad. It was found that by recessing the endplate, thereby creating a weak divergent lens the spherical aberration of the system could be nearly cancelled, resulting in a final miscollimation of 0.06 mrad over a 2- in. diam. When the collimated beam was focused by a lens, an off-axis radial ellipticity was discovered, the origin of which was found to be chromatic aberration resulting from the Boersch effect.
Analysis of Gas Mixtures Using Data from Pulsed Vacuum Networks
Authors: Pulfrey Robert , Kendall B. R. F.
Published: July 2002

A numerical method for extracting gas mixture compositions from pulsed vacuum network data is discussed. The problem of imposing boundary conditions is considered. Results of the analysis of several artificial gas mixtures are presented.
Optical modulation in thin films
Authors: Taylor H. F.
Published: July 2002

Thin-film optical modulators may find widespread application in communications and information processing systems because of their high bandwidth, low electrical power requirements, and compatibility with other thin-film components. A thin-film modulator consists of a dielectric waveguide and an appropriate electrode structure. An applied electric or magnetic field or a traveling acoustic wave alters the dielectric tensor of the film and/or substrate in such a manner as to change the amplitude, phase, or frequency of the guided light wave. Materials have included semiconducting III–V and II–VI compounds, LiNbO3, and nitrobenzine liquid for electro-optic devices, garnets for magneto-optic devices, and glass films on quartz and LiNbO3 substrates for acousto-optic devices. This paper will review the theory of dielectric waveguides and input-output coupling as well materials, fabrication techniques, and performance characteristics for the various types of thin-film modulators.
Adsorption properties of surface modified silica
Authors: Erdel G. , Unger K.
Published: July 2002

By surface reactions on finely divided silica (aerosil) and porous silica the following functional groups were attached on the surface: TMS, TPS, BS, and SBS. Surface modification of aerosil has no significant influence on the adsorption of nitrogen with one exception: the adsorption capacity decreases slightly by replacement of polar hydroxyls by nonpolar TMS groups. A distinct splitting of the isotherms of benzene on aerosil and its derivatives was observed. The isotherms of methanol are most widely separated with adsorption capacity in the sequence sample with SBS groups > original sample > sample with BS groups > sample with TPS groups > sample with TMS groups. The same variation of the adsorption behavior was obtained for porous silica and its modified products. The effect is more pronounced due to the pore structure.
Emission uniformity enhancement between microfabricated tips in cold cathode arrays
Authors: Schwoebel P. R. , Spindt C. A. , Holland C. E. , Panitz J. A.
Published: July 2002

The current–voltage characteristics can vary significantly between individual microfabricated tips in as-fabricated arrays of cold cathodes. Such emission nonuniformity is undesirable in device applications. We have shown that in situ tip self-heating by the emitted electron current can be used to make the current–voltage characteristics of microfabricated field emitter tips nearly identical to one another. The improved emission uniformity will allow for more reliable array operation at increased electron emission current densities.
Technique employing gold nanospheres to study defect evolution in thin films
Authors: Mirkarimi P. B. , Baker S. L. , Stearns D. G.
Published: July 2002

A technique is described in which commercially available colloidal gold solution is used to deposit monodisperse gold nanospheres with diameters ranging from 20 to 60 nm directly onto silicon wafers. The technique for depositing the gold nanospheres is straightforward and requires little in terms of infrastructure or resources. The wafers containing gold nanospheres are first characterized by techniques such as atomic force microscopy and transmission electron microscopy, after which they are coated with a thin film and recharacterized. This enables one to quantitatively study the evolution of thin-film defects nucleated by small substrate particles. An example is provided where the technique is used to study the evolution of defects in Mo/Si multilayer films, which is of significant importance in the development of reticles for extreme ultraviolet lithography.
Measurement of carbon film thickness by inelastic electron scatter
Authors: Bryson Charles E. , Vasilyev Leonid , Linder Robert , White Richard L. , Thiele Jan-Ulrich , Coffey Kevin R. , Brannon James H.
Published: July 2002

The electron spectra obtained from magnetic media coated with carbon films of varying thickness are presented. Electrons backscattered inelastically dominate the spectra. The intensity of the elastic peak varies in accordance with the Beer/Lambert law and escape depths of 30 and 43 Å for 1 and 2 keV primary beam energies, respectively. The maximum intensity in the inelastic scatter portion of the spectrum decreases in energy and magnitude with increasing film thickness. The spectral differences associated with changes in carbon film thickness are large and provide an alternative to x-ray photoelectron spectrometry for quantitative carbon film thickness measurement.
Composition profile of heat treated carbon nitride hard coatings
Authors: Böhme O. , Yang S. , Teer D. G. , Albella J. M. , Román E.
Published: July 2002

Carbon nitride (CNx) hard coatings, prepared by unbalanced dc magnetron sputtering of carbon in an argon / nitrogen atmosphere, have been studied using Auger electron spectroscopy and x-ray photoemission spectroscopy. The films were deposited on silicon substrates at about 250 °C and reached a saturation value of the nitrogen to carbon ratio of 0.17. This value was increased by the presence of chromium at the interface layer to the substrate. The in-depth composition of the CNx hard coatings was found to be homogeneous, even after heat treatment up to 800 °C in ultrahigh vacuum (UHV). However, the UHV heat treatment resulted in diffusion processes and chemical interactions at the interface to the substrate.
Development of a data-driven dynamic model for a plasma etching reactor
Authors: Zhang Haiyang , Nikolaou Michael , Peng Ying
Published: July 2002

We compare several parameter identification methods for data-driven identification and validation of an empirical linear dynamic model for a helicon plasma reactor. The model relates easily measurable process variables to ellipsometry measurements from which the etch depth can be determined in real time. The potential use of such a model for process control is obvious. The model developed shows improvement over a neural network model developed in a previous study based upon the same data.
Substrate preparation and low-temperature boron doped silicon growth on wafer-scale charge-coupled devices by molecular beam epitaxy
Authors: Calawa S. D. , Burke B. E. , Nitishin P. M. , Loomis A. H. , Gregory J. A. , Lind T. A.
Published: July 2002

Silicon charge-coupled devices (CCDs) are extensively used for commercial and scientific imaging in the visible to near-infrared wavelength range of 450 to 850 nm. Ground-based astronomers require large-scale high-performance CCDs with high sensitivity at wavelengths from the 320 nm atmospheric cutoff to 900 nm. We report on wafer-scale low-temperature silicon molecular beam epitaxy to enable ultraviolet (UV) detection utilizing silicon-fabrication-facility-compatible surface preparation. Characterization of the UV response-enhanced backside-illuminated CCDs fabricated with this technique show near 100% internal quantum efficiency in the wavelength range of 200 to 900 nm.
Cluster-ion implantation: An approach to fabricate ultrashallow junctions in silicon
Authors: Lu Xinming , Shao Lin , Wang Xuemei , Liu Jiarui , Chu Wei-Kan , Bennett Joe , Larson Larry , Ling Peiching
Published: July 2002

Cluster-ion implantation in combination with two-step annealing is effective in making ultrashallow junctions. We have demonstrated the use of heavy atom–boron cluster ions to effectively reduce the boron energy for shallow-junction formation. SiB, SiB2, and GeB cluster ions have been used to produce 2 keV boron for low-energy ion implantation. We have generated the SiB, SiB2, and GeB cluster ions using the source of negative ions by cesium sputtering ion source. Shallow junctions have been made by SiB, SiB2, and GeB cluster ions implanted into Si substrates at 1×1015/cm2 with energies at 6.88, 8.82, and 15 keV, respectively. We also discussed the benefit of a 550 °C preannealing before a 1000 °C, 10 s rapid thermal annealing.
Thickness Measurements of Thin Permalloy Films: Comparison of X-Ray Emission Spectroscopy, Interferometry, and Stylus Methods
Authors: Silver M. D. , Chow E. T-K.
Published: July 2002

Magnetic properties of vacuum-evaporated thin Permalloy films for memory applications are affected greatly by the thickness of the film as well as by the composition and various evaporation parameters. X-ray emission spectroscopy is generally used for thickness measurements and composition studies. In this paper, the thicknesses of nickel-iron films (81 to 82% nickel and 400- to 3560-Å thickness range) are compared by a stylus method (Talysurf), a high resolution multiple beam interferometer (Tolansky-type), and x-ray fluorescence analysis with calibrated standards. Data are presented showing that the x-ray method is the most reproducible and allows rapid calibration and computation by computers.
Abstract: Energy dissipation in catalysis
Authors: Steinbrüchel Ch. , Schmidt L. D.
Published: July 2002

The dissipation of the reaction energy and its possible consequences in catalysis on supported metal crystallites are considered. The modes and times required for energy dissipation can influence reaction rates by processes involving excited intermediate molecules at the surface and by producing locally high catalyst temperatures. The boundary resistance at the metal-crystallite-insulator-support interface is shown to play a significant role in determining the temperature-time behavior of a catalyst crystallite. Calculations indicate that crystallite temperatures may be several hundred degrees higher than that of the substrate. A distinct size effect is also predicted with small crystallites attaining much higher temperatures than large ones. The latter may be important in determining the stability of catalysts toward sintering.
Electrical conduction through thermal and anodic oxides of InSb
Authors: Wilmsen C. W. , Vasbinder G. C. , Chan Y. K.
Published: July 2002

The characteristics of current flow through thermally and anodically grown oxides of vapor deposited and bulk InSb are reported. The magnitude of the current though the thermal and anodic oxides are found to be markedly different. The thermally grown oxides have very low resistance similar to In2O3. The anodic oxides are insulating and the current flow is characteristic of Schottky emission. The anodic oxides grown on bulk single crystals (BSC) and on thin films deposited at 150° and 350°C have essentially the same current−voltage characteristics. The breakdown strength of the BSC oxides is approximately 50% greater than of the thin film oxides.
Abstract: Electron beam deposition of alumina to rf modulated steel substrates
Authors: Komiya Souji , Mizuno Masayasu
Published: July 2002

Radiofrequency modulation has been applied in an ion plating process for an insulator material. Alumina was evaporated from a 270° bent electron beam source. Heat dissipation at the substrate surface with respect to deposition rate and rf power input was measured by a calorimetric method. Films deposited at various conditions of substrate temperature and rf power were assessed. The effect of rf modulation was observed on appearance of films formed at low temperatures (220°C) and on fractured sections at high temperatures (410°C).

For films formed at 280°, 360°, and 410°C on either steel or molybdenum sheets, no differences in pin hole, adhesion, and film composition can be detected due to the effect of rf modulation.
Abstract: Fabrication and electrical properties of insulated thin film inductors
Authors: Jennings Thomas A. , Chen Stephen T.
Published: July 2002

A process for the fabrication of multiturn inductors is described. Inductors are prepared by depositing alternate oxide and metal films through a series of suitable masks. The inductors have a concentric square or rectangular configuration, and the axis of the core is normal to the substrate. An empirical expression, similar to that given by Grover,1 was developed and relates the inductance to the physical dimensions and number of turns of the coil. The dependence of the quality factor (Q) on frequency and the self−resonant frequency on oxide thickness were investigated.
Abstract: Tight binding, hybrid orbital description of the electronic structure and bonding properties of the FCC transition metals
Authors: Helms C. R. , Yu K. Y.
Published: July 2002

To study the electronic structure of transition metal surfaces, the theoretical model employed should be capable of properly reproducing the electronic structure of the bulk. In this paper we describe a tight binding scheme using sd hybrid orbitals, which gives a good description of the bulk bands and can also be used conveniently to study surface electronic structure. The method used is similar to the interpolation scheme of Hodges, Ehrenreich, and Lang, except that we use a 6×6 sd block and neglect the three remaining higher energy states. Application of the model to the band structures will be presented and the extension of the model to surface calculations for a [110] surface discussed.
Local and nonlocal effects in the theory of physisorption
Authors: Landman Uzi , Kleinman George G.
Published: July 2002

A review of our microscpic theory of physisorption is presented. The effects of spatial dispersion in the metal for two boundary conditions at the metal surface are discussed and compared with results of the local−dielectric−response theory. It is shown that in the presence of spatial dispersion the Van der Waals interaction decreases more rapidly than the d−3 law of the local theory. In both cases, an adequate determination of the attractive energy requires an accurate description of the dynamic polarizability of the incident atom. Repulsive contributions to the interaction energy are included via the density−functional formalism, resulting in a complete description of the interaction energy curve. The equilibrium distances of the atom are a monotonically increasing function of the metallic−electron density and are not affected significantly by nonlocality in the metal.
Abstract: The dynamics of dissociative chemisorption: CH4 on rhodium
Authors: Stewart Charles N. , Ehrlich Gert
Published: July 2002

In contrast to the rapid dissociative adsorption of diatomic gases on the transition metals, chemisorption of methane and ethane occurs slowly and with an appreciable activation energy. In order to explore the molecular events in this activated adsorption we have examined the interaction of methane with a rhodium crystal, using a field emission microscope equipped with a variable temperature molecular beam source. From studies on clean surfaces prepared by field evaporation it appears that activation of the gas alone is sufficient to bring about adsorption, and that the activation energy for this process is 7 kcal/mol. Measurements have also been carried out on variously deuterated methanes. These reveal that for methane, excitation of the gas to higher vibrational states is the significant step in the passage over the barrier to disociative chemisorption.
Abstract: Energy loss mechanisms in low−energy electron scattering from (100) tungsten
Authors: Luscher P. E.
Published: July 2002

The loss spectrum of low energy (0<Ep<300 eV) electron scattering from (100) tungsten has been experimentally investigated and mechanisms giving rise to fine structure studied. A very narrow, dense unoccupied conduction band state has been observed to function strongly in interband excitations involving the conduction bands, core orbitals, and adsorbed atoms. Interband excitations involving the tungsten 5p and 4f core orbitals and the 2s and 2p orbitals of adsorbed oxygen have been identified. Two separate binding states of adsorbed oxygen have been observed in the loss spectrum. The surface plasmon has been dissected from its position adjacent to the bulk plasmon and the ∠10 eV loss relegated to interband origins. The positions in energy of the bulk and surface plasmons as well as the low energy interband structure have been shown to be reasonably consistent with the available optical data.
Abstract: Studies on the (0001) surface of cobalt
Authors: Berning G. L. P.
Published: July 2002

LEED studies on cobalt single crystals are reported here for the first time. cobalt undergoes a phase change at 420°C, which makes the cleaning of cobalt single crystals very difficult. Above 420°C cobalt changes from a hep to a fee structure, and upon cooling some of the fee structure still remains. The surface can be cleaned, however, by heating to 315°C, argon-ion bombjardment, and the removal of adsorbed carbon by oxidation, and the subsequent removal of oxygen with hydrogen. The clean surface gives the diffraction pattern expected with no surface reconstruction. The I-V curves show strong kinematic behavior and the main features can be explained in a simple manner. A well-defined complex diffraction pattern appears after contamination with CO. This diffraction pattern can be explained by measns of the same reciprocal net derived for a diffraction pattern observed for S on Ni(111).1 This reciprocal net is for a pseudo square-unit mesh with six equivalent positions that gives coincidence with the substrate at points, such that the coincidence mesh dimensions are √39 larger than the nearest substrate neighbor spacing. It is also found that faceting occurs with mainly oxygen on the surface.
Oil backstreaming in turbomolecular and oil diffusion pumps
Authors: Maurice Louis , Duval Pierre , Gorinas Guy
Published: July 2002

State of the art turbomolecular pumps have oil vapor backstreaming rates too low to measure by classical methods (AVS method, metal-foil gravimetry, quartz piezoelectric method, or drop microvolumetry). The authors analyzed the rarefied gases in the chamber; however, great care must be taken to prevent the probe from reacting with the residual atmosphere in the chamber. Experiments clearly demonstrate that oil backstreaming is primarily a function of time: any oil vapor present in the system will eventually find its way into the chamber. Backstreaming was measured in a number of gas bearing and ball bearing turbomolecular pumps as well as in up to date diffusion pumps with minimal backstreaming. A gas bearing turbomolecular pump exhausting to atmosphere through a dynamic seal is the only type completely free of oil vapor backstreaming, regardless of operating time. Today’s oil diffusion pumps have backstreaming rates comparable to those of turbomolecular pumps backed by oil-sealed forepumps.
Sputtering of two-phase polycrystalline metals
Authors: Tortorelli P. F. , Altstetter C. J.
Published: July 2002

Polycrystalline niobium and its alloys with oxygen have been sputtered with a 15-keV argon ion beam. Yield measurements and scanning electron microscope topographic observations have been made for both single- and two-phase (Nb + NbO) targets which were also characterized by use of a scanning Auger microprobe. Results indicate that the relative yields of different phases, as well as of different grains, are critically dependent on the direction of the argon beam with respect to the individual grain orientations. Oxygen in solid solution and oxygen-containing atmospheres were important factors which influenced the target topography. The observed differential erosion of grains and the presence of surface relief inside individual grains are discussed with reference to the use of sputtering for depth profiling in surface analysis.
Electronic structure calculations of interfaces and overlayers in the 1980’s
Authors: Herman Frank
Published: July 2002

After reviewing some recent developments in the calculation of the electronic structure and atomic arrangements of semiconductor interfaces and overlayers, we discuss the directions that such calculations are likely to take during the next decade.
Adherence of ion beam sputter deposited metal films on H-13 steel
Authors: Mirtich M. J.
Published: July 2002

An electron bombardment argon ion source was used to sputter deposit 17 different metal and metal oxide films ranging in thickness from 1 to 8 μm on H-13 steel substrates. A tensile test apparatus was used to quantitatively measure the film adherence to the substrate surface. Comparisons in bond strength were made between ion beam, ion plating and rf deposited films. This study was the first of a three phase program to find a protective coating to prevent heat checking in H-13 steel dies used for aluminum die casting. The results of exposing the coated substrates to temperatures up to 700 °C are also presented.
Reactively sputter-deposited high-emissivity tungsten carbide/carbon coatings
Authors: Wickersham C. E. , Foster E. L. , Stickford G. H.
Published: July 2002

Stable adherent high-emissivity tungsten carbide/carbon coatings have been deposited onto iridium and carbon/carbon substrates by reactively sputtering a cemented tungsten carbide target in an acetylene–argon atmosphere. The thin, light-weight, high-emissivity coatings have potential for improving the heat transfer characteristics and reducing the weight of satellite thermoelectric generators. The tungsten carbide/carbon coating emissivity increased from 0.35–0.91 as the acetylene partial pressure during deposition increased from 0–0.133 Pa. Auger electron spectroscopy, x-ray diffraction, and electron microprobe analysis of the coatings revealed that the film structure and composition changed from β-WC1-x to an amorphous carbon-rich material as the acetylene partial pressure exceeded 0.034 Pa. One-micron-thick tungsten carbide/carbon films on iridium withstood vacuum anneals at 1775 K for 19 h without significant degradation in the coating durability or emissivity.
Characterization of thin films for laser systems using surface analytical techniques
Authors: Humpherys T. W. , Lusk R. L. , Jungling K. C.
Published: July 2002

High performance laser systems require dielectric thin film coatings applied to optical components in order to satisfy various functional requirements such as polarization suppression, wavelength selection, and specular reflection enhancement. In addition to high incident radiation levels, these coatings are sometimes subjected to UV radiation and active gasses, i.e., HF/DF mixtures for 2.5 to 4.1 μm laser systems. Thorium tetrafluoride and zinc sulfide coatings in particular have been found to degrade with time and exposure. This degradation is analyzed by means of Scanning Auger Microscopy, x-ray Photoelectron Spectroscopy, Secondary Ion Mass Spectroscopy, and Secondary Electron Microscopy. The validity of these types of analyses is demonstrated. Investigations reveal several defects and abnormal oxygen content in these coatings which may eliminate these materials from further use in high energy laser applications and other systems which require durability and sustained performance.
Evaluation of ISABELLE full cell ultrahigh vacuum system
Authors: Foerster C. L. , Briggs J. , Chou T. S. , Stattel P.
Published: July 2002

The ISABELLE full cell vacuum system, consisting of a 40 m long by 8.8 cm diam stainless steel tube pumped by seven pumping stations, was assembled and processed for 10−12 Torr operation. Evaluation and testing of the system and its subassemblies has been completed. Detail design of system components and the determination of the conditioning process was completed. The best procedure to rough pump, leak test, vacuum bake the system, condition pumps, degas gauges, turn on ion pumps, and flash sublimation pumps was established. Pressures below 2×10−11 Torr are now routinely achieved in normal operation of the full cell. This includes pump down after replacement of various components and pump down after back fill with moist unfiltered air. The techniques developed for the full cell will be used to build the ISABELLE ultrahigh vacuum system.
Surface reconstruction and interface formation in Si and GaAs
Authors: Katnani A. D. , Stoffel N. G. , Edelman H. S. , Margaritondo G.
Published: July 2002

We investigated the effects of substrate surface reconstruction upon the interface formation between In and Ge overlayers and Si(111)2 × 1, Si(111)7 × 7, and GaAs(110) substrates. Photoemission spectroscopy with synchrotron radiation was used to monitor the evolution of the interface parameters—Schottky barrier height or band discontinuities—as a function of the overlayer thickness. All interfaces involving Si(111)7 × 7 substrates exhibited a characteristic evolution pattern with saturation at 1.4–1.8 monolayers coverage. The interfaces involving Si(111)2 × 1 substrates instead exhibited faster evolution saturating below a monolayer coverage with marked differences between individual cleaved surfaces. A similarly rapid evolution was observed for the interfaces involving GaAs(110) substrates. These results indicate that the spectrum of intrinsic surface states is different for Si(111)2 × 1 and for Si(111)7 × 7. In particular for Si(111)7 × 7 a large density of localized states exists near the Fermi level.
Multipolariton modes of a compound semiconducting surface depletion layer
Authors: Quinn J. J. , Eguiluz Adolfo , Wallis R. F. , Das Sarma S.
Published: July 2002

The coupled higher multipole plasmon-optical phonon modes (multipolariton modes) of a simple two-step model of a semiconducting surface depletion layer are studied in the long wavelength nonretarded limit.
Matrix effects in SIMS: Ion yield enhancement in copper sulfide films on copper and copper alloys
Authors: Hammer G. E.
Published: July 2002

Matrix effects have been observed in positive SIMS spectra produced by Ar+ bombardment of copper sulfide films formed on copper and its alloys. The relative enhancement in copper ion yield has been measured to serve as a preliminary correction in the application of semi-quantitative analysis of the sulfide films. Surfaces of copper, copper sulfide, and copper oxide on copper were analyzed by using both dynamic (profiling) and quasi-static SIMS. Relative enhancement factors for copper ion yields were determined for both types of analysis. The ion yield increases in going from metal to sulfide to oxide. The enhancement factor for SIMS profiling of the sulfide films was found to be nearly constant for sulfur concentration between 30% and 10%. SIMS analysis has been performed on a sulfide film formed on a copper–zinc alloy. The enhancement factors were shown to correctly scale the signal from the sulfide film relative to that from the metal substrate, compared to simultaneous AES signal strengths.
Effects of alloying and chemisorption on Auger line shapes in Cu-Pd
Authors: Sundaram V. S. , Landers R. , da Cunha S. P. , Rogers J. D. , Laks B. , Kleiman G. G.
Published: July 2002

We present the results of a systematic experimental investigation of the Auger line shape in Cu-Pd alloys. By comparing the results of x-ray and electron stimulated Auger spectroscopies, we are able to separate distinctive surface sensitive contributions to the Cu–M23 VV Auger line shape. The results are discussed within the context of our present understanding of screening and of the systematics of Auger line shapes. Comparison with theory indicates that the observed effects may be due to surface electronic structure changes.
Initial stages of high-temperature metal oxidation
Authors: Yang C. Y. , O’Grady W. E.
Published: July 2002

In this paper we will discuss the application of XPS and UPS to the study of the initial stages of high-temperature (≳350 °C) electrochemical oxidation of iron and nickel. In the high-temperature experiments, we have electrochemically oxidized iron and nickel electrodes in contact with a solid oxide electrolyte in the UHV system. The great advantages of this technique are that the oxygen activity at the interface may be precisely controlled and the ability to run the reactions in UHV allows the simultaneous observation of the reactions by XPS.
Ideal and relaxed surfaces of SiC
Authors: Lee D. H. , Joannopoulos J. D.
Published: July 2002

During the past few years there has been considerable interest in the relaxation of GaAs(110) and Si(100)-(2×1) surfaces. The surfaces of SiC, however, provide an intermediate system between these heteropolar and homopolar structures. It is interesting therefore to investigate the kinds of relaxation that might occur at the zincblende and wurtzite surfaces of SiC. We perform calculations using Chadi’s energy minimization scheme, with the coefficients of linear, quadratic, and cubic energy correction terms fitted to the bulk lattice constant, bulk modulus, and thermal expansion coefficient. To check the validity of this model, we calculate six experimentally known phonon frequencies. The agreement between theory and measured values is quite good. With this model, we investigate the relaxation at the SiC(110) surface in the zincblende structure and SiC(101̄0) and (112̄0) surfaces in the wurtzite structure. The results show a combination of downward movement and buckling for all three surfaces. The reduction in total energy is about 0.21 eV/atom for the (110) surface, and 0.24 eV/atom, 0.18 eV/atom for (101̄0) and (112̄0), respectively. Further results include the determination of ideal and relaxed electronic structure and optimum relaxed geometries. Finally, a new theory which extends Chadi’s scheme to do first principles phonon calculations is presented and discussed.
Study of space–charge effect by computer
Authors: Sasaki Tateaki
Published: July 2002

The space–charge effect in high density electron beams (beam current ∠2 μA) focused by a uniform magnetic field is studied computationally. On an approximation of averaged space– charge force, a theory of trajectory displacements of beam electrons is developed. The theory shows that the effect of the averaged space–charge force appears as a focal length stretch. The theory is confirmed not only qualitatively but also quantitatively by simulations. Empirical formulas for the trajectory displacement and the energy spread are presented. A comparison between the empirical formulas and some theoretical formulas is made, leading to a severe criticism on the theories of energy spreads.
Auger depth profiling and preferential sputtering of platinum nickel silicide
Authors: Morgan A. E. , Ellwanger R. C.
Published: July 2002

Auger depth profiling measurements are presented of platinum nickel silicide films grown on n-Si and on n+-Si by annealing a sputter-deposited Pt0.4Ni0.6 alloy layer at 500 °C for 20 min in N2. Quantification of the profiles is achieved by calibration with standards. The silicide composition varies with depth and at the interface is PtxNi1−xSi with x≪1. Also, total sputtering yields and preferential sputtering coefficients are given for 2 keV, 45°, Ar+ bombardment of the elements and their binary and ternary silicides. The amount of preferential sputtering is practically independent of projectile energy (0.5–5 keV) and of substituting Xe+ for Ar+. However, its variation with composition complicates the quantitative analysis of nickel.
Monte Carlo model of topography development during sputtering
Authors: Rossnagel S. M. , Robinson R. S.
Published: July 2002

A Monte Carlo computer model has been developed to describe a surface undergoing low energy (<keV) ion bombardment. The model incorporates angle-dependent sputter yields, angle-dependent reflection of energetic particles, random redeposition of sputtered material, and random surface migration of impurities. The model is two-dimensional and describes a surface in cross section as a line. The initial surfaces can be of any general form, not necessarily simple geometrical forms as in some earlier models. Two general results have been developed with this model. The first is that with the inclusion of sputtering, reflection, and redeposition, structures are developed similar to those observed experimentally. These features are temporary, however, and will be eventually eroded. If surface diffusion to a nucleation site is included as well, stable, enlarging structures are formed.
Valence band study of Mg2Si by Auger spectroscopy
Authors: Bevolo A. J. , Shanks H. R.
Published: July 2002

Previous XPS measurements of Mg2Si revealed three valence bands which were all assigned to the Si 3s and 3p states based on a completely ionic model of the bonding in Mg2Si that assumed no occupied Mg 3s or 3p states. Auger spectroscopy is element specific so that the local density of states of Mg and Si can be measured separately. The L1L23V and the L23VV Auger spectra of Mg in Mg2Si were measured from a single crystal of Mg2Si cleaved in UHV. The L23VV spectrum showed the involvement of the Mg 3p state in the upper two valence bands in agreement with recent calculations. More surprisingly the L1L23V spectrum gave evidence of the presence of the Mg 3s state in the lowest energy valence band that had not been predicted. The Auger results gave evidence of covalency in the bonding of Mg2Si.
Influence of aluminum adatoms on the oxidation of germanium at room temperature
Authors: Katnani A. D. , Perfetti P. , Zhao Te-Xiu , Margaritondo G.
Published: July 2002

A study of photoemission spectra of the core levels and of the valence band taken with synchrotron radiation shows that ultrathin Al overlayers (0.4–2 Å) dramatically increase the room temperature oxidation rate of Ge(111) surfaces for oxygen exposures exceeding 106 L (langmuirs). We estimate the oxide thickness over which an enhanced growth rate has been observed in this experiment not to exceed 10 Å. We explored the initial oxidation stage searching for an explanation of this effect. Although no complete explanation was found, the results clarified that the initial chemisorption phase is similar to the ‘‘intermediate-oxide’’ phase observed during the oxidation of metallic Al rather than to an oxide of Ge and Al.
Nuclear spin polarization of solid deuterium–tritium
Authors: Souers P. C. , Fearon E. M. , Mapoles E. R. , Gaines J. R. , Sater J. D. , Fedders P. A.
Published: July 2002

It appears that parallel alignment of deuteron and triton magnetic moments increases the cross section of the nuclear reaction T(d,n) He4 by 50%, thereby promising a laser driver of perhaps half the original energy. Both ‘‘brute-force’’ and dynamic nuclear polarization are considered and the many potential problems of the latter are considered. High nuclear polarization by the dynamic technique requires a small nucleus-to-unpaired electron ratio, a long longitudinal nuclear relaxation time and a short longitudinal electron relaxation time. Normal D–T is shown to be inadequate, and enriched and possibly very pure molecular DT will be required. The key variable is the nuclear relaxation time, which can either depend on the interaction with rotationally excited impurity molecules or on paramagnetic defects formed by the tritium radiation. Radiation-induced DT decomposition and rotational catalysis will combat one another to affect the DT purity. The expected atom density and fractionation effects are considered. There exists one frequency at which both D and T atoms can be pumped.
An aluminum alloy quadrupole mass filter with a 120-m-long rf cable
Authors: Watanabe F. , Ishimaru H.
Published: July 2002

An aluminum alloy quadrupole mass filter and a new transmitting technique for rf power have been developed for the 30-GeV TRISTAN ring. The aluminum alloy quadrupole electrodes are produced with a special surface treatment by oxygen gas spraying, and the quadrupole is assembled in a new way without screw clamps. The rf amplifier and tank coil wound on a toroidal core can be separated with a 120-m-long coaxial cable. Thus, the part fitted on the analyzer is small and simple and is also resistant to radioactive environments and to heat. The newly developed ionizer has a closed hemispherical mesh anode and can be degassed at high temperatures above 1000 °C by electron bombardment of 50 W. This quadrupole mass filter has a high sensitivity of 1.4×10−3 A/Torr at a resolution of 40 and an rf frequency of 2.5 MHz without a secondary electron multiplier.
Scanning Auger microprobe studies of ball cratered CdS/CuInSe2 solar cells
Authors: Levenson L. L. , Burnham N. A. , Matson R. J. , Noufi R. , Kazmerski L. L.
Published: July 2002

CdS/CuInSe2 solar cell films are typically several micrometers thick. Composition profiles of these films are usually carried out on fracture cross sections by scanning Auger microscopy or by recording Auger spectra during ion milling. For fracture cross sections, the depth resolution depends on the electron beam diameter and the roughness of the fracture surface. Ion milling is time consuming, and artifacts are caused by ion beam faceting. Ball cratering requires only a fraction of an hour and provides significant magnification of the film cross section. There is sufficient contrast, both in optical and electron microscopy, to distinguish between CdS and CuInSe2 layers. Auger line scans and point analyses across crater walls have been used to determine composition depth dependence. Artifacts associated with this technique are electron beam damage of CdS and CuInSe2 during line scan analysis and smearing of CdS for short distances (∼1 μm) along the crater wall during ball cratering.
X-ray and Auger-electron yields for quantitative element analysis
Authors: Jitschin W. , Werner U.
Published: July 2002

Quantitative analytical work frequently relies on calibration measurements in which empirical parameters are determined whose interconnection to basic physical properties is unsatisfactory. In contrast, the fundamental processes of x-ray absorption and emission are known with reasonable accuracy a priori and are insensitive to the state of matter. The present paper discusses recent results on these inner-shell processes obtained with synchrotron radiation. Absorption cross sections show a smooth energy dependence by a power law; minor dispersion like deviations from this behavior due to electron correlations are now established. Precise x-ray and Auger yields can be determined by a novel technique in which the fluorescence is detected for various primary energies in the realm of the absorption edges.
Electron stimulated desorption of H+, O+, and OH+ from H2O adsorbed on niobium
Authors: Rey S. , Román E. , de Segovia J. L.
Published: July 2002

H2O layers adsorbed on polycrystalline niobium at a temperature of about 150 K have been studied by means of the electron stimulated desorption (ESD). The O+, H+, and OH+ surface ions are recorded by maintaining the surface under continuous electron bombardment and corresponding to the dissociated species O, H, and OH, respectively. When the surface is exposed to H2O with no e− bombardment the ESD ions are H+ and OH+, with very low, if any, O+ yield. The origin of the ion species has been determined on the basis of their thresholds and ion energy distribution. The ionization of the Nb 4p core level at about 30 eV is responsible for the ejection of H+ from the Nb–H or Nb–O–H bonds, and the O+ from the Nb–O bond. A Nb surface atom ‘‘multiadsorbate’’ bonds model of the dissociated products, H and OH, is proposed to explain the origin of the various ESD ion species. The influence of the e− bombardment on surface species and the thermal desorption spectra of the H2O layer are also presented. The first one shows that the e− bombardment increases significantly the surface species yielding O+ ESD ions and a model for its formation is proposed. The thermal desorption spectrum of mass 16 (O) at relatively low temperatures has its origin from ESD of neutral O atoms.