bluuebunny/crossref_metadata_2025 huggingface dataset:
Flatness and Surface Roughness of Some Common Thin Film Substrate Materials
Authors: Anderson R. M. , Neudeck G. W.
Published: July 2002

The flatness and roughness of nine common substrate materials (quartz flat, Corning 7059 glass, Corning 0211 glass, soft glass, AlSiMag 614, AlSiMag 614 with 743 glaze, AlSiMag 772, mechanically polished silicon, and chemically polished silicon) are reported. Corning 0211 and the three alumina samples had a flatness on the order of 1 part/thousand. Corning 7059, soft glass, and both silicon samples had a flatness on the order of 0.1 part/thousand. The quartz flat had a flatness on the order of 2×10−3 part/thousand. AlSiMag 614 and 772 exhibited a roughness of 10 000 and 5000 Å average peak to peak, respectively. Chemically polished silicon exhibited a roughness of ∼300 Å. The quartz flat, Corning 7059 glass, Corning 0211 glass, soft glass, AlSiMag 614 with 743 glaze, and the mechanically polished silicon all exhibited a roughness on the order of or below the resolution limit (∼50 Å) of the measuring instrument.
Effects of Some High-Voltage Conditioning Processes on Tungsten Electrodes
Authors: Maley J. J.
Published: July 2002

The effects of electrical, gas, and heat conditioning on the physical characteristics of projections, or whiskers, on tungsten electrodes have been investigated. The use of a cylindrical projection tube to obtain current-voltage characteristics and the interpretation of this data by Fowler-Nordheim plots has lead to a better understanding of physical processes occurring at the cathode during high-voltage conditioning processes. It was found that typical surface parameters, such as, emitting area, field enhancement, critical breakdown field, and the number of whiskers on the cathode vary considerably, depending on the type of conditioning the cathode received.
Isothermal Effusion Sources for Vacuum Deposition of Solid Solutions
Authors: Holloway H. , Hohnke D. K. , Crawley R. L. , Wilkes E.
Published: July 2002

An effusion technique for vacuum deposition of solid solutions is described. The method uses a pair of effusion cells whose temperature fluctuations are arranged to occur in phase. This permits a considerable improvement in the compositional homogeneity of alloy films. The method has been applied to solid solutions of IV–VI compounds.
Sputtering Multilayered Conductor Films
Authors: Muth D. G.
Published: July 2002

Rf sputtering techniques were used to deposit multilayer conductor films with Au as the top conducting layer. Appreciable interdiffusion of the layered films occurred during sputtering, with a resultant increase in the Au resistivity. The heating attributable to electron bombardment during sputtering caused the films to heat to 290 °C at 0.5 kW of applied power, and as high as 550 °C at 2.0 kW. After sputtering a two-layer film of NiChrome-Au at 1.0 and 2.0 kW, for example, Ni and Cr were detected throughout the 12 000-Å Au layer. When sputtering at 2.0 kW, the underlying NiCr film also reacted with the Au to form an intermetallic compound, Au4Cr. Other conductor film systems included in this study were Ti–Au, Ti–Pd–Au, Ta–Au, and Mo-Au.
Compositional Control of Tantalum–Aluminum Alloy Films by a dc Biased, ac Sputtering Technique
Authors: Steidel C. A. , Jaffe D. , Kumagai H. Y.
Published: July 2002

The deposition of a wide range of controlled compositions from a fixed electrode and substrate geometry is demonstrated for Ta–Al alloy films using a unique dc biased 60-Hz ac sputtering technique. Sputtering takes place from sets of water-cooled Ta and Al tubular rods which alternate as anode and cathode during a high voltage ac cycle. Alloy compositions over the range of 72–5 at.% Al were obtained by systematically varying a series dc bias applied to the Ta rods from 0 to −1600 V. Reproducibility at a given bias voltage was found to be approximately ±3 at.% Al. Possible mechanisms by which the dc bias affects film composition are discussed.
Ion Scattering Spectrometry
Authors: Goff R. F.
Published: July 2002

A sensitive method of surface composition analysis is obtained through monitoring the binary scattering of low energy noble gas ions from surface atoms. Such analyses have been shown to be accomplished with simplified instrumentation and to be primarily sensitive to the first atomic surface layer. The technique has been extended to include the direct examination of electrically insulating surfaces, and examples of surface compositions obtained from ceramic and glass will be presented. With the capability of examining surfaces irrespective of their electrical conductivity, multilayer thin film structures become a prime example of the dual utilization of the probe ion beam to both analyze and simultaneously controllably remove surface atoms. Such a depth composition profile will be shown for a TiO2 thin film sandwich in which interface contamination was found. Quantitative aspects of the technique will be shown in the SiOx system. Diverse applications of surface analyses will also be shown on metal, semiconductor, and some select alloy surfaces.
A New Technique for High Speed Anodization in a dc Oxygen Glow Discharge
Authors: O’Hanlon J. F. , Sampogna M.
Published: July 2002

In this paper a new technique for high speed anodization in a dc oxygen discharge is reported. A 0.0025-cm-diam wire biased 50 V positive with respect to the anode caused a ten- to fifteenfold increase in the anodization rate. Rates as high as 30 A/ min were observed with a sample current denisty of 1.15 mA/ cm2. With a current density of 0.21  mA/ cm2 the Faraday efficiency was 15%. It is postulated here that the observed effects are due to increased surface ionization of adsorbed atomic oxygen.
Measurement of the Growth of Oxide Layers on Metals by Low-Energy Electron Spectroscopy: Aluminum
Authors: Murata Yoshitada , Ohtani Shunsuke
Published: July 2002

The energy-loss spectra of 350-eV electrons reflected from aluminum were observed during the oxidation of a freshly evaporated film. The loss spectra due to surface plasma showed characteristic variations in the process of oxidation. The thickness of the oxide layer was measured by using the dispersion relation of surface plasmons. This method was shown to be useful for studying thin oxide layers (<20 Å). Oxide films grew on aluminum in different ways when the pressures were 1×10−7 and 1×10−8 Torr, where most of the residual gas was hydrogen and water. In the former case, the oxide layer in the initial stage was islandlike, whereas in the latter case it was uniform. Oxide films grew abruptly about 20 min after evaporation of the aluminum, as was confirmed by an analysis of the residual gas. The rate of growth of uniform oxide layers was consistent with a logarithmic law.
Field Emission Study of Silicon on Tungsten
Authors: Swenson O. F. , Sinha M. K.
Published: July 2002

Small amounts of silicon evaporated onto a clean tungsten tip in ultrahigh vacuum show two distinct types of surface diffusion. At about 550 °K boundary free diffusion occurs on the [111] zones. Above 950 °K diffusion occurs with a sharp boundary and an activation energy of 1.5 eV. The activation energy of thermal desorption of silicon from tungsten depends on the surface coverage and varies from 5.6 to 6.2 eV. Annealing the silicon covered tip at ≈ 1400 °K causes diffusion of silicon into the interior of tungsten and produces a different and stable pattern, probably that of a tungsten silicide with a work function of 4.8 eV.
A molecular beam study of reactive nucleation of thin films: magnesium on germanium single crystals
Authors: Matysik K. J. , Voorhoeve R. J. H. , Carides J. N.
Published: July 2002

The reactive nucleation of Mg on Ge(100), (111), and (211) surfaces was studied with the molecular beam technique. In this system Mg reacted with the substrate to form a semiconducting germanide Mg2Ge. For incident Mg fluxes of 1012–1013 cm−2 sec−1, the germanide nucleated at substrate temperatures of the order of 350°C. Nucleation of the germanide on Ge(100) occurred at submonolayer Mg coverages indicating an island configuration for critical nuclei of Mg2Ge. A HCP–Mg film could be grown by depositing on substrates held at room temperature. HCP–Mg films of the order of 102–103 monolayers alloyed rapidly at 125°C to form the germanide.
Electrical resistivity of polycrystalline bismuth films
Authors: Joglekar A. V. , Karekar R. N. , Sathianandan K.
Published: July 2002

Electrical resistivity of polycrystalline bismuth films was studied. The size effect theory in addition to the grain boundary scattering theory of Mayadas and Shatzkes has been applied to the data to explain resistivity—thickness dependence.
Structure and morphology of obliquely deposited CdTe films
Authors: Dhere Neelkanth G. , Pinheiro Roberto G. , Parikh Nalin R.
Published: July 2002

Structure and morphology of CdTe films deposited in vacuum, on glass substrates, at oblique vapor incidence angles and at substrate temperatures up to 250 °C, have been studied by reflection-electron diffraction and scanning-electron microscopy, so as to help in the understanding of their unusually high photo-electromotive force. Thinner films developed sphalerite type of face centred cubic (c) structure with a0=6.48 Å. Thicker films showed additional wurtzite type of hexagonal close packed (h) phase with a0=4.57 Å, c0=7.47 Å, and a large hexagonal (H) phase, a0=4.57 Å, c0=11,27 Å, with a corresponding reduction in the proportion of the c phase. For oblique vapor incidence, 1 − d {111} orientation of c phase and 1− d {00.1} orientation of h phase, both being close packed layers showed normal or only slightly oblique growth, while 1 − d {331} orientation of c phase and 1 − d {10.3} orientations of hexagonal phases showed oblique growth towards the vapor direction but not aligned with it. Hillock growth of deposits was observed, with the hillocks forming rows normal to or at an angle to the vapor direction. The leeward side of the hillocks is controlled by the vapor direction. This side called by us, the growth direction is tilted towards but is not aligned with the vapor direction. It has been indicated that, as against the model based on the mismatch between adjacent hillocks, for explaining the high photo-emf, that based on the transition between cubic and hexagonal structures is in better conformity with the results.
Plasma Panels
Authors: Haberland Peter H.
Published: July 2002

Both the ac-plasma panel and the Self Scan (trademark) panel have found application in display systems. Color capability and different brightness levels have been demonstrated. Some device and design parameters for the panel are discussed, and the operation of the two types of display devices is analyzed.
Modulation of the Optical Guided Wave by uv Light and Electron Beam Excitations
Authors: Toyoda Koichi , Namba Susumu , Matsui Toshiaki , Suge Yoshio
Published: July 2002

An effective modulation of a He–Ne laser beam at a wavelength of 6328 Å guided in a semiconductor ZnS thin film has been obtained when the guided wave travels transversely across the region irradiated by intense uv light. This seems to be caused by the absorption effect by means of the optically excited free carriers. The modulation ratio has shown monotonic increase with the excitation intensity. At maximum excitation, a modulation ratio of 35% was obtained. For normal transmission of a laser beam through the excited shallow region near the surface, measurements of reflectance change and phase retardation have been also carried out under uv light and pulsed electron excitations, are discussed in connection with the absorption effects by the free carriers generated by these excitations. In the case of excitation by an electron beam of 15 mA and 30 kV, the fractional increase of the absorption was 1×10−3.
Masking of deposited thin films by means of an aluminum-photoresist composite
Authors: Grebe K. , Ames I. , Ginzberg A.
Published: July 2002

Masking of deposited thin films has been achieved through the use of a composite mask consisting of a positive acting photoresist layer and an overlying aluminum layer. The overlying aluminum layer acts as a deposition mask which is spaced away from the substrate at a distance equal to the thickness of the underlying photoresist layer. The photoresist layer, which acts to keep the aluminum layer in close proximity to the substrate, is patterned through the use of the overlying aluminum layer as an exposure mask. Recession of the edges of the photoresist layer is achieved by overexposure and subsequent development.
Chemical bonding at metal-semiconductor interfaces
Authors: Phillips J. C.
Published: July 2002

Trends in the I–V characteristics of metal-semiconductor interfaces can be analyzed in terms of the atomic configurations at interfaces as well as the redistribution of electronic charge which occurs because of chemical bonding at the interface. The atomic configurations, in turn, depend on the thermal history of the interface, which can be discussed from several points of view. The chemical bonding picture can be contrasted with the more traditional approach based on surface states, such as those associated with dangling bonds on free semiconductor surfaces.
Electron beam probe studies of semiconductor-insulator interfaces
Authors: Bottoms W. R. , Guterman D.
Published: July 2002

An electron beam of diameter as small as 100 Å may be employed to study MOS structures, providing information about the surface topography (secondary electron imaging), surface chemical composition (Auger electron spectroscopy), bulk chemical composition (x-ray fluorescence), as well as the structure of interface regions with high spatial resolution. The penetration depth of the beam and therefore of the excited volume can be altered by adjusting the accelerating voltage and the incident angle. Images of the internal surfaces of MOS structures are formed due to variatons in the metal-insulator barrier height, the semiconductor-insulator barrier height, defects within the oxide or at the interfaces, and topography causing localizing high-field conditions. These mechanisms give rise to small ac signals in the current induced across the structure by the electron beam. These signals may then be amplified and used to modulate the intensity on a CRT. Several different structures have been observed at the interfaces in MOS systems using this technique. Electrical measurements and bias thermal stressing experiments have been used to determine the nature of the structures responsible for observed images.
Optimization of InxGa1−xAs/InyAl1−yAs high electron mobility transistor structures grown by solid-source molecular beam epitaxy
Authors: Zheng H. Q. , Radahakrishnan K. , Yoon S. F. , Ng G. I.
Published: July 2002

We report on the optimization of InP-based InxGa1−xAs/InyAl1−yAs pseudomorphic high electron mobility transistor (PHEMT) structures to achieve the highest possible two-dimensional-electron gas (2DEG) density and mobility. The layer structures are grown by solid-source molecular beam epitaxy with a valved phosphorus cracker cell. The single-side-doped PHEMT structure with a δ-doping concentration of 6×1012 cm−2 exhibits a 2DEG sheet density of 3.93×1012 cm−2 with a mobility of 11100 cm2/V s at 300 K. The double-side-doped PHEMT structure with a bottom δ-doping concentration of 1×1012 cm−2 and a top δ-doping concentration of 5×1012 cm−2 gives a 2DEG sheet density of 4.57×1012 cm−2 with a mobility of 10 900 cm2/V s at 300 K. The electrical, optical and structural properties of the PHEMT structures were characterized by Hall, photoluminescence, and x-ray diffraction measurements.
Effects of Be on the II–VI/GaAs interface and on CdSe quantum dot formation
Authors: Guo S. P. , Zhou X. , Maksimov O. , Tamargo M. C. , Chi C. , Couzis A. , Maldarelli C. , Kuskovsky Igor L. , Neumark G. F.
Published: July 2002

The effects of Be on the II–VI/GaAs interface and on CdSe quantum dot (QD) formation were investigated. A (1×2) surface reconstruction was observed after a Be–Zn coirradiation of the (001) GaAs (2×4) surface. ZnBeSe epilayers grown after the Be–Zn coirradiation show very high crystalline quality with x-ray rocking curve linewidths down to 23 arcsec and a low etch pit density of 4×104 cm−2, and good optical quality with a band-edge photoluminescence (PL) emission peak linewidth of 2.5 meV at 13 K. However, ZnBeSe epilayers grown after Zn irradiation alone have poor crystalline quality and poor optical properties. Atomic force microscopy measurements show that CdSe QDs grown on ZnBeSe have higher density and smaller size than those grown on ZnSe. A narrower PL emission peak with higher emission energy was observed for the CdSe QDs sandwiched by ZnBeSe. These results indicate that the formation of CdSe QDs as well as the II–VI/GaAs interface are modified by the presence of Be.
Approach for a self-assembled thin film edge field emitter
Authors: Tsai J. T. H. , Teo K. B. K. , Milne W. I.
Published: July 2002

A self-assembled thin film edge emitter has been fabricated. The unique fabrication process requires only a tetrahedral amorphous carbon (ta-C) thin film with one photolithography step to generate a three-dimensional structure. A high emission site density was achieved compared with that obtained from a flat ta-C film emitter using the same measurement technique. In the high field regime the emission obtained was based on the Fowler–Nordheim emission mechanism. Using the Fowler–Nordheim equation we calculated the field enhancement factor of this emitter to be 80. The potential of ta-C thin films as hard masks for silicon etching in KOH solution was also investigated.
Optical Film Materials and Their Applications
Authors: Hass Georg , Ritter Elmar
Published: July 2002

This paper gives a survey of materials suitable for the preparation of dielectric films for interference coatings, highly reflecting metallic films, and semitransparent coatings for neutral density filters and sunglasses. It is shown that improved vacuum-deposition techniques and treatments, such as evaporation by electron bombardment, film deposition under ultrahigh vacuum conditions and at extremely high rates, reactive evaporation in an oxygen atmosphere, and ultraviolet irradiation after the film deposition, have greatly increased the number and improved the quality of film materials for optical applications. The most important factors for producing dielectric films with high transmittance and metallic coatings with high reflectance are discussed. Coatings suitable for controlling the temperature of satellites and space vehicles are described.
Test of the Critical Theory of Electrical Breakdown in Vacuum
Authors: Kranjec Pavel , Ruby Lawrence
Published: July 2002

The critical-field theory of electrical breakdown in vacuum is shown to be applicable to all of the twelve metals and to the one alloy tested. In this theory the electric field at breakdown is predicted to be independent of gap spacing when the field considered is that existing in the neighborhood of cathode field-emission sites. This field is enhanced with respect to the average gap field by a factor which can be calculated from measurements of the field-emission current prior to breakdown. A vacuum tube has been employed for the experiment in which one electrode is movable and in which foils may be used for the electrode materials. The critical field for breakdown compares well with that calculated by others in the four metals for which previous data exist.
A Mass Spectrometer without Memory Effect for Gas Analysis in Ultrahigh Vacuum
Authors: Gentsch H.
Published: July 2002

The described Omegatron mass-spectrometer is equipped with an internal heating device. All inner metal parts of the Omegatron gauge axe made of noble metal and can be held during the measurements at a maximum temperature of ≈ 500 °C. For cleaning and degassing the gauge the temperature of the metal parts can be increased up to 900 °C. All parts of the gauge made of base metals are enamelled. The fact that the memory effect can be held down by the entirely heatable Omegatron is a new and important criterion for measurements of partial pressures in the ultrahigh vacuum range. A further advantage of the heatable Omegatron-box is the remarkable constancy of ion transmission which is obtained at constant electrode-potentials even after many heating-cycles.
AC Impedance of Space-Charge Barriers
Authors: Maserjian J.
Published: July 2002

The ac impedance has been considered in a general way which includes the effect of a distribution of trapping states within Schottky-type energy barriers. Starting with the complete unipolar transport equation, and introducing a density-of-trapping-states function, depending generally on both position and energy, one arrives at a useful formulation of the ac impedance. This result is possible because of the rapid variation of the effect of traps in such barriers which restricts their main contribution to a narrow range of positions and energies. Thus, expressions are obtained which relate the ac impedance measurements to the trapping effect at regions of the barrier corresponding to the applied frequency, voltage, and temperature. With these three independent variables, it is possible to experimentally scan the barrier over energy and position, obtaining a profile of trap densities and other barrier properties as well as independent tests on the selfconsistency of the method. Some experimental results obtained from thin-film Nb2O5 capacitors are given and shown to be in general agreement with the theory. This agreement also supports our contention, based on previous dc studies, that the Nb2O5 film contains a large ionic space charge. From the results we calculate a barrier minimum of 0.38 eV, an average trap density of about 1019 cm−3 eV−1, and trap capture cross section of about 10−13 cm2.
Redeposition of sputtered species during ion etching of Cu, Ag, and Au
Authors: Miller Alfred C. , Czanderna A. W.
Published: July 2002

The redeposition of sputtered Au, Ag, and Cu onto glass surfaces, which are in the same plane as bombarded metal foils, has been established by ion scattering spectrometry. Sites near the sputtering center were analyzed with sensitivities of 0.0008–0.001 monolayers after neon bombardmant of the foils for up to two hours. From the data, the redeposition coverage is estimated to be from 0.0094 to 0.042 monolayers after two hours of Ne bombardment at 1500 eV. The electric field of the incident ion beam, acting on low-energy sputtered ions, is a likely cause of the redeposited material.
Generation and extraction of microsecond intense relativistic electron beams
Authors: Schneider R. , Stallings C. , Cummings D.
Published: July 2002

The Physics International Pulserad 1140 has been modified so that a pulse length of 1.7 μsec can be obtained with a beam energy of 50 kJ. This modification involves substituting a pulse-forming network for the conventional Blumlein. This long-pulse generator has been used to study diode behavior on 1-μsec time scales. The dependence of impedance on voltage and anode–cathode spacing is discussed here. A semiempirical model has been developed. The diode time history and closure velocity are discussed in terms of this model.
Electron-beam lithography using vector-scan techniques
Authors: Speth A. J. , Wilson A. D. , Kern A. , Chang T. H. P.
Published: July 2002

A computer-controlled electron-beam microfabrication system has been developed for evaluation of micron and submicron lithographic technologies. Direct large-field-device exposures of complex patterns have been processed for FET and bubble memory fabrication. Experimental exposures have also been made to allow mask fabrication for alternative exposure apparatus. The system exposes the electron-sensitive resist by sequentially filling in pattern elements (cells), whose geometry and size are determined by an off-line pattern data processor. Abutting line scans, using a round electron probe, are used to expose each cell. The system normally exposes fields up to 4 mm square. Deflection resolution is 14 bits per axis. Exposure rate, pattern registration, pattern field adjustments (size, position offset, rotation, and orthogonality), and workstage position are among the functions which have been automated.
Electron scattering and line profiles in negative electron resists
Authors: Heidenreich R. D. , Ballantyne J. P. , Thompson L. F.
Published: July 2002

Starting with a depth-dose theory of electron energy dissipation in negative electron resists and a quasimonoenergetic Gaussian scattering theory, we derive theoretical expressions for single-line profiles using the exposure parameters of the Bell Laboratories electron-beam exposure system (EBES). These profiles are calculated by convoluting the Gaussian scattering distribution with the experimentally determined relationship between resist thickness remaining after development and input electron dose. Calculated profiles for the negative electron resist P(GMA-co-EA) agree well with experimental results for the range of feature sizes exposed on EBES. Since features on EBES are built up by multiple passes, the theory is extended to line profiles separated by the address structure of EBES. The calculated resist profiles are in reasonably good agreement with experimental results. The observed profile heights are somewhat greater than predicted by theory since the developed gel is not perfectly rigid and gel interaction takes place between neighboring profiles. The results show the importance of good gel rigidity and high contrast for negative electron resists used in high resolution applications. The range of validity of the trends predicted by the quasimonoenergetic theory for increasing film thickness and operating voltage are extended using a Monte Carlo approach which includes the effects of energy loss. The calculated trends have led to the choice of optimum exposure conditions for EBES.
Synthesis of various oxides in the Ti−O system by reactive evaporation and activated reactive evaporation techniques
Authors: Grossklaus W. , Bunshah R. F.
Published: July 2002

Many metal−gas systems exhibit several equilibrium compound phases of significantly different properties. The Ti−O system has the compounds TiO, Ti2O3, Ti3O5, and TiO2. Some of these exhibit phase transformations with change in temperature. This investigation deals with the synthesis and high rate deposition of these compounds using the reactive evaporation (RE) and activated reactive evaporation (ARE) processes. Ti is evaporated from a rod−fed eb source in the presence of a partial pressure of O2. Both the metal and gas atoms are activated or partially ionized. It was found that the various oxides are synthesized and deposited as predicted by the equilibrium diagram with the higher oxides produced with increasing partial pressures of oxygen. Higher oxides were produced with the ARE process than with the RE process at a constant oxygen pressure, thus demonstrating the higher efficiency of the ARE process. It was also shown that the TiO2 (rutile phase) can be deposited at temperatures as low as 450°C.
Reduction of nodules in electron-gun-evaporated Au films
Authors: Feinstein L. G. , Bill M. J.
Published: July 2002

When gold is evaporated from an electron beam source, spitting from the molten charge results in nodules on the deposited film. Au was evaporated from carbon and tungsten crucibles in an attempt to understand and reduce nodule formation. A carbon scum on the melt surface, nonwetting of crucible walls, and crucible surface roughness are all felt to contribute to nodule production. W-2% ThO2 crucibles with a 0.4 μ surface finish have been employed for Au evaporation, as they exhibit the following advantages: (1) Exceptionally long life and virtual indestructibility; (2) an evaporation rate 2–3 times higher than that for carbon crucibles; and (3) 15 nodules ≳ 13 μ diam per 100 cm2 substrate, at a deposition rate of 12 000 Å/min.
Comparison of photovoltaic and photoconductive effects in insulating CdS crystals
Authors: Kramer Bernard , Wallmark John T. , Mark Peter
Published: July 2002

Photovoltage measurements with insulating CdS crystals capacitively coupled to the external circuit have been performed at room temperature in 1 atm oxygen and 10−8 Torr vacuum, and at 100 K at 10−8 Torr vacuum, and have been interpreted self consistently with photoconductivity measurements. It was found that the Dember voltage is about 0.06 V at room temperature and 0.02 V at 100 K, that the oxygen chemisorption-induced surface barrier is at least 0.15 eV at room temperature, and that photoconductivity measurements are a valuable tool in the self-consistent interpretation of photovoltage measurements on an insulating specimen.
Principles and applications of selective solar coatings
Authors: Jurisson J. , Peterson R. E. , Mar H. Y. B.
Published: July 2002

Several ways that selective coatings can be used to enhance the performance of solar energy collection systems are reviewed. Coatings discussed include vacuum-deposited, electroplated, and paint-type selective solar absorber coatings and vacuum-deposited and chemically etched antireflection and infrared reflecting coatings for glass. The optical and physical requirements for the coatings, as well as their effectiveness at increasing solar collector performance, are discussed.
Analytical transmission electron microscopy of thin films
Authors: Geiss R. H. , Huang T. C.
Published: July 2002

A detailed investigation of the various physical properties of the interfacing of a Si(Li) energy dispersive spectrometer (EDS) to a transmission electron microscope (TEM) has shown that for a Philips 301 TEM the best physical location for the detector is in the port usually accomodating the anticontamination cold finger and as close to the sample as possible. The optimum tilt of the sample has been found to be 36° and the optimum voltage is actually the highest available. By the use of a strong prefield objective lens, it is possible to obtain reliable quantitative elemental analysis from areas as small as 25 nm diam. Various correction schemes and the use of a powerful profile fitting technique allow for recovery of spectra with overlapping peaks under the worst possible conditions. Using a straightforward analysis scheme the data may then be reduced to elemental composition with an accuracy and precision on the order of 1%, which is far better than has been reported in literature for TEM−EDS thus far. All of this was obtained with no loss in the nominal high resolution and diffraction capabilities of the TEM.
High−spatial resolution Auger spectroscopy and Auger integration applications
Authors: Pocker D. J. , Haas T. W.
Published: July 2002

The general approaches to higher spatial resolution Auger spectroscopy as well as the motivation for and relative merit of selected area or point probe analysis are briefly reviewed. A selected area system consisting of a commercial field emission−type scanning electron gun integrated into an existing ultrahigh vacuum Auger system is demonstrated (secondary electron image resolution <0.2 μ, Auger spectra of features <2 μ). The Auger spectrum integration and related signal processing utilized to recover acceptable spectra from the low−current/high−noise field emission gun excitation are outlined. Finally, the enhancement of high−energy Auger features observed with the 10−20 keV primary electron irradiation is quantitatively reported for selected elements utilizing integral Auger spectra.
Glow discharge optical spectroscopy measurements of arsenic-implanted silicon
Authors: Marcyk G. T. , Streetman B. G.
Published: July 2002

Recent advances in the glow discharge optical spectroscopy (GDOS) technique have been made, as shown by measurements of implanted arsenic profiles in silicon. The improvements discussed include the use of krypton as a discharge gas, a dual detection system which permits simultaneous measurements of the impurity distribution and the substrate sputtering, and the use of nickel as an overcoat to allow accurate measurements near the surface. Profiles of as-implanted and 1000°C annealed samples are presented which agree substantially with other types of measurements.
Electronic structure at an abrupt GaAs–Ge interface
Authors: Baraff G. A. , Appelbaum Joel A. , Hamann D. R.
Published: July 2002

The potential, charge density, and interface states have been calculated for the ideal interface between intrinsic GaAs, terminated on a (100) Ga plane, and intrinsic Ge. The conduction band is found to be nearly continuous across the interface and only a small interface dipole moment is found. Even though the two crystals, Ge and GaAs, have the same crystal structure and lattice parameters (a situation which might be thought to produce an interface containing no states in the forbidden gap at the Fermi level), a simple quantum-mechanical counting argument shows that there must be interface states at the Fermi energy for the unreconstructed interface. These states are the band-picture equivalent of unsaturated bonds. We find that fractional occupancy of the interface bonds (each of which contains 1.75 rather than two electrons) arises via a single partially occupied band of interface states. Consideration of the electronic energy suggests that the actual interface will be reconstructed.
Auger depth profiling of thick insulating films by angle lapping
Authors: Tarng M. L. , Fisher D. G.
Published: July 2002

It is demonstrated that the chemical composition of thick and multilayer insulating films can be easily depth profiled by Auger electron spectroscopy by laterally scanning an angle-lapped region that reveals the entire depth to be profiled. Conventional depth profiling of such structures is often difficult because of unstable sample charge-up conditions that occur when Auger measurements are made during ion milling. The angle-lap technique is nondestructive, in that it allows one to reexamine the entire profile whenever desired. It is thus particularly suitable for investigation of samples with initially unknown or trace impurities. Also, this technique is free of depth-resolution degradation and differential sputter yield effects usually associated with long-term ion milling of thick films. The absolute depth resolution of the angle-lap–Auger profiling method is independent of the film thickness and is equal to the electron beam diameter plus sample manipulator resolution divided by the angle-lap lateral magnification. An ultimate depth resolution of ∠35 Å would be possible using a 0.5-μm-diam beam, a 0.2° lap, and a 0.5-μm manipulator resolution. This is approaching the depth resolution associated with the finite escape depth of Auger electrons. Using a 10-μm electron beam and a 0.5° angle lap in the present study, a depth resolution of about 1000 Å was obtained, as predicted. The oxygen concentration in oxygen-rich polysilicon films measured by this technique agrees with that measured by an Electron Probe Microanalyzer. The Auger data also suggest that all oxygen atoms in the films are bonded to silicon in the form of SiO2.
Mass spectrometric study of plasma etching
Authors: Raby Bruce A.
Published: July 2002

A quadrupole mass spectrometer gives much useful information about plasma etching processes on silicon and its compounds. The present work confirms some of the known or postulated chemistry in the plasma and raises further questions about the understanding of the process. The instrument enables dynamic optimization of process parameters and provides a variety of diagnostic information. In particular, it allows the detection of etching endpoints and thereby provides a sensitive technique for controlling the etching process. The technique appears to substantially reduce or eliminate the need for calibration. The account discusses endpoints for polycrytalline silicon, silicon dioxide, silicon nitride, and some cases involving photoresist.
Determination of quantitative sputter rates of iron oxide by Auger electron spectroscopy (AES) and ellipsometry
Authors: Hart Robert G. , Simmons Gary W.
Published: July 2002

AES was used to study the sputtering rates for thermally grown iron oxide films bombarded with 1–5-keV Ar+. Ellipsometric measurements of the films were used to determine the film thickness and to confirm composition. Calibration was made for sputtering rates as a function of ion flux and ion energy. Special attention was placed upon the effects of specimen−ion source and specimen−electron energy analyzer alignment in establishing this calibration. This work is relevant to experiments in which ion etching is used as a means of obtaining depth profiles of oxidized iron and ferrous alloys.
Niobium nitride thin-film SQUID’s biased at 20 MHz and 9.2 GHz
Authors: Wolf S. A. , Rachford F. J. , Nisenoff M.
Published: July 2002

Niobium nitride thin films have been reactively sputtered onto cylindrical quartz substrates. Films 500 Å or thicker, exhibited superconducting transition temperatures in the range 15–16 K, thinner films had lower Tc’s. Good 20-MHz SQUID behavior was noted in samples incorporating variable thickness weak links in which the ’’local’’ critical temperatures are depressed to about 12 K. Some of these SQUID’s exhibited nearly intrinsic magnetic flux noise. Correlations were obtained between the ratio of quasiparticle diffusion distance to the zero-temperature coherence length and the quality of the SQUID behavior.
Some performance tests of a microarea AES
Authors: Todd G. , Poppa H.
Published: July 2002

A UHV microarea Auger analysis system that has submicron Auger analysis capability is described. Capabilities of this versatile surface research system include secondary electron imaging, microarea Auger analysis in both EdN/dE and EN (E) modes, macroarea AES, sputter ion cleaning, and a multiple specimen handling facility. A thermal field emission Zr/W(100) source is used for microarea AES. A spatial resolution of 1000 Å in the secondary electron image is demonstrated. Auger line scans in both EdN/dE and EN (E) modes show submicron edge resolution under nonideal specimen conditions.
Direct, electron lithographic fabrication of silicon devices and circuits
Authors: Yau L. D. , Thibault L. R.
Published: July 2002

The Bell Laboratories Electron Beam Exposure System (EBES) together with sensitive electron resists have been used to produce low-noise microwave bipolar transistors with features of one-micron and n-channel MOS circuits, such as 4096-bit random access memories with minimum dimensions of two microns. Both negative and positive resists were used. The negative resist was poly (glycidyl methacrylate-co-ethyl acrylate) (COP), and the positive resist was poly (butene-1-sulfone) (PBS). In some cases, the device processing required modification to accomodate the properties of the electron resist used. The transfer of the resist patterns into the circuit material employed wet and dry etching processes. Unlike other electron-beam lithographic systems which require chip-by-chip realignment procedure, EBES realigns the wafer at three points only. The results show a level to level registration of wihin 1/4 μm.
Imaging and alignment tests on an electron projection system
Authors: Livesay W. R.
Published: July 2002

Improvements to an Electron Projection System are described which eliminate many of the reported disadvantages to this type of system. The performance of a field-compensating electrostatic chuck that remedies pattern distortion caused by the wafer (anode) is described in conjunction with imaging and alignment tests on 75-mm-diam wafers. Proximity effects and reimpacting backscattered electron flooding are shown to be minimized by reduction of the electron exposure energy thereby eliminating the need for pattern compensation in the mask. Line and space patterns with 0.5-μm dimensions were exposed and resolved without compensation for exposure dosage of larger patterns. Overlay registration results are given for two-layer alignment tests using e-beam-fabricated masks to expose 75-mm-diam wafers.
Self-consistent study of the (2×1) reconstructed Si(111) surface
Authors: White C. T. , Ngai K. L.
Published: July 2002

Si(111) surfaces formed by cleavage in ultrahigh vacuum initially exhibit a 2×1 LEED pattern which is replaced by an effective 1×1 pattern upon annealing at moderate temperatures. Concomitant with the replacement of the 2×1 structure with the 1×1 pattern, a large change in the electronic workfunction is observed. To study the 2×1 and its transformation, we have constructed a model based on Harrison’s idea of dehybridization energy-mediated reconstruction. Results obtained from a self-consistent analysis of this model show that a 2×1 pattern, corresponding to a split dangling bond band, is unstable at several hundred degrees Kelvin towards an effective 1×1 pattern with an unsplit dangling bond band and appreciably higher Fermi level consistent with experiment.
Study of semiconductors using electrochemical techniques
Authors: Morrison S. Roy
Published: July 2002

A nonmathematical description of current flow across the semiconductor–electrolyte boundary is presented. The description of active ions in solution is reviewed in terms of their acceptor or donor energy levels, the fluctuation of these levels, and the mechanism of electron transfer to or from these levels. With no such active ions (in other words, with an inert electrolyte), in principle electron transfer cannot occur. The use of such an inert electrolyte as a contact to make measurements of the bulk properties of the semiconductor is emphasized. The advantages and disadvantages of such a liquid as opposed to a metallic layer as a contact in C–V studies is discussed.
AES studies of chemical shift and beam effect on molybdenum oxides
Authors: Lin T. T. , Lichtman David
Published: July 2002

Auger electron spectroscopy (AES) studies of the MNN spectra of MoO3, MoO2, oxidized Mo foil, and Mo (100) single crystal reveal the splitting of the Auger transition peaks which involve valence electrons. The splitting of these transition peaks is attributed to the altered valence-band density of states which illustrates the existence of two major oxidation states in the specimen. The additional state is caused either through surface oxidation or beam-induced reduction. Based on the M4,5N2,3V transition peak, the measurement shows the chemical shift to be 5 eV for Mo6+ and 1 eV for Mo4+. The reduction of the oxygen Auger peak-to-peak height (APPH) with a simultaneous enhancement of the Mo APPH and sample coloration change in the beam-irradiated area has been observed during electron bombardment of oxide specimens. The observable changes indicate the occurence of beam-induced decomposition and the preferential loss of oxygen from the surface. The electron bombardment mainly causes the reduction of MoO3 to MoO2. The efficiency of further reduction to the elemental metal state is low as compared to the reduction process from Mo6+ to Mo4+. Comparison of predicted Auger intensities, based on the contribution to the total Auger intensity from each atomic plane, with the experimental observations confirms the formation of a Mo4+-rich surface layer on a beam-irradiated specimen.
Operation and maintenance of a diffusion-pumped vacuum system
Authors: Hoffman Dorothy M.
Published: July 2002

Sources of contamination in a diffusion-pumped vacuum system are detailed. Means of minimizing these are described. Proper pumping procedures are suggested, with particular stress placed on the use of dry N2 purge gas.
Characterization of amorphous barium titanate films prepared by rf sputtering
Authors: McClure D. J. , Crowe J. R.
Published: July 2002

The physical and electrical properties of amorphous BaTiO3 films prepared by rf sputtering have been investigated as a function of rf power, substrate temperature and bias, and sputtering gas pressure and composition. A charge storage capacity of ∠0.04 C/m2 was found for films prepared in pure argon on substrates held at near room temperture during deposition. These films showed a dielectric constant of ∠14 with little dependence on frequency or temperature. No evidence for ferroelectric behavior was observed. Inadequate substrate cooling yielded films which had very high dissipation factors and low breakdown strengths. The addition of oxygen to the sputtering gas resulted in films which exhibited a strong temperature coefficient of capacitance which increased at low frequencies. Oxygen additions produced a change in the titanium to barium ratio present in the films and gave rise to increases in the dielectric dissipation factor, the dc conductivity, and the defect density.
Complex impedance of copper films
Authors: Howard Lorn L. , Turner Dee A.
Published: July 2002

Thin (approximately 1500 Å) evaporated bismuth films having initial resistance values between 30 and 150 Ω/square have been shown previously to have a structure-determined impedance in the infrared region between 2 and 15 μm. The electric circuit representing this impedance was derived from a combination of resistance and infrared transmission measurements. For evaporated copper films of similar thickness and for the same infrared region an impedance has been determined using infrared transmission and reflection measurements instead. The most useful circuit obtained is similar to the one derived for bismuth: a capacitance in series with a parallel capacitance and resistance. For copper films having a range of initial values of resistance from 30 to 260 Ω/square the equivalent circuits together with R- and C-parameter values are determined and presented.
AES investigation of the chemical structure of silicon oxy-nitride films
Authors: Madden H. H. , Holloway P. H.
Published: July 2002

The silicon-L2,3VV, nitrogen-KVV, and oxygen-KVV Auger signals have been measured for a series of chemical-vapor-deposited silicon nitride films in which the oxygen content varied from 2 to 67 at. %. Uncorrected derivative spectra and background-corrected, loss-deconvoluted integral lines for silicon nitride films, for clean Si, and for SiO2 were compared. The silicon spectra indicate that a high-energy Si-L2,3VV feature from the nitride, previously identified with elementally bound Si, actually indicates an oxygen impurity. The N-KVV lineshape is found to be insensitive to oxygen incorporation while the three-peaked oxygen line becomes broader with increasing oxygen content. The valence-electron distribution width in the nitride is more than twice that of the distribution in elemental Si, but the width does not change appreciably with changing oxygen content. These Auger data indicate that oxygen incorporation into silicon nitride results in the formation of oxynitrides for ≲ 200 ppm of oxygen in the reactor. Beyond this concentration, silicon oxide is largely formed.
Versatile UHV sample transfer system
Authors: Clausing R. E. , Heatherly L. , Emerson L. C.
Published: July 2002

A vacuum transfer system has been developed that allows samples to be inserted from air into an Auger analyzer. Following an initial analysis they may then be moved to and from a separate vacuum chamber for other studies. The system is constructed of standard UHV components and can be fabricated to cover any desired transfer distance. All-metal sealed valves isolate the various chambers so that the vacuum integrity of each is maintained. The sample size is limited only by the smallest constriction within the components, which is 2 cm in the system described. The transfer is rapid and is capable of being controlled remotely for use in a hostile environment.
Lattice-matched heterostructures as Schottky barriers: HgSe/CdSe
Authors: Best J. S. , McCaldin J. O.
Published: July 2002

A novel structure, which is both a lattice-matched heterostructure and a Schottky barrier, is fabricated by epitaxial growth of (111) oriented HgSe on (0001) oriented CdSe. Hydrogen transport CVD is used, with a HgSe source temperature of 420°C and a CdSe substrate temperature of 330°C. Single crystal growth was obtained. Of the two orientations possible for the crystal symmetries involved, only one was observed for a given specimen. The ’’Schottky barrier’’ height for this lattice-matched heterostructure is 0.73±0.02 eV as measured by the photoresponse method. This uncertainty is substantially less than is usual for Schottkies. The magnitude is greater by about one-quarter volt than is achievable with the most electronegative elemental metal, Au, in qualitative agreement with work function arguments.