bluuebunny/crossref_metadata_2025 huggingface dataset:
Mist/Steam Cooling in a Heated Horizontal Tube—Part 1: Experimental System
Authors: Guo Tao , Wang Ting , Gaddis J. Leo
Published: July 2002

To improve the airfoil cooling significantly for the future generation of advanced turbine systems (ATS), a fundamental experimental program has been developed to study the heat transfer mechanisms of mist/steam cooling under highly superheated wall temperatures. The mist/steam mixture was obtained by blending fine water droplets (3∼15 μm in diameter) with the saturated steam at 1.5 bars. Two mist generation systems were tested by using the pressure atomizer and the steam-assisted pneumatic atomizer, respectively. The test section, heated directly by a DC power supply, consisted of a thin-walled (∼0.9 mm), circular stainless steel tube with an ID of 20 mm and a length of 203 mm. Droplet size and distribution were measured by a phase Doppler particle analyzer (PDPA) system through view ports grafted at the inlet and the outlet of the test section. Mist transportation and droplet dynamics were studied in addition to the heat transfer measurements. The experiment was conducted with steam Reynolds numbers ranging from 10,000 to 35,000, wall superheat up to 300°C, and droplet mass ratios ranging from 1∼6 percent. [S0889-504X(00)02402-8]
The Omega Method–An Engineering Approach to Life Assessment
Authors: Prager Martin
Published: July 2002

Many petroleum companies have been using a tool developed by MPC for evaluating materials operating in the creep range. This method has now been recognized for inclusion in API RP579 on fitness-for-service. This paper reports on the method and explains the materials properties used therein. The MPC Omega method concentrates on the application of estimates of performance of materials at low design level stresses. The database upon which the materials properties are based was acquired by testing service exposed and softened steels and minimizing environmental effects. Use of the MPC properties in some cases could increase allowable stresses. However, the great advantage of the method is its capability as a tool for predicting strains, benchmarking materials, incorporation into finite element analysis, developing sensible testing strategies, and dealing with realistic stress situations. [S0094-9930(00)02903-6]
Thermal Energy Storage in Soils at Temperatures Reaching 90°C
Authors: Gabrielsson A. , Bergdahl U. , Moritz L.
Published: July 2002

Using soil and groundwater for heat storage offers an opportunity to increase the potential for renewable energy sources. For example, solar heating in combination with high temperature storage, e.g., using ducts in the ground, has the potential of becoming an environment friendly and economically competitive form of heat supply. Technology is developed to reduce ground construction costs and to ensure that adequate attention is paid to the geotechnical potentials and limitations of such systems, in the temperature range between neutral ground temperature up to 90°C. Investigations of real plants and in the laboratory have given valuable knowledge on the thermal effects on clayey soils as well as on the surroundings of high temperature stores in soft clay. The operational function of heat stores, with respect to heat transfer capacity of ground heat exchangers and heat losses, can be predicted with good agreement. For the uppermost part of the temperature range, long term performance, cost verification and thermal endurance of materials involved including the storage medium, is recommended using a full-scale demonstration plant. [S0199-6231(00)00901-1]
rf-Sputtered Cadmium Sulfide “Thin Crystals”
Authors: Lagnado I. , Lichtensteiger M.
Published: July 2002

rf-sputtering techniques have been employed in a diode configuration for the deposition of cadmium sulfide films up to 5 mμ thickness on nonoriented substrates. X-ray diffractometer tracings showed exclusively (000l)peaks with l=2,4,6,⋯, indicating a highly preferred basal plane orientation parallel to the substrate. Electron diffraction patterns, moreover, indicate essentially the same structural features as those obtained from single crystal cadmium sulfide. Results based on x-ray double crystal spectrometry and electrical transport properties will be presented as related to sputtering parameters such as rf-power density, argon pressure, substrate temperature, and deposition rate.
Electron-Beam Fabrication
Authors: Broers A. N.
Published: July 2002

Electron-beam fabrication techniques are becoming of increasing interest as thin-film electronic devices get smaller and the need for quick turn-around in their fabrication becomes more important. This short paper outlines the current state of electron-beam fabrication technology and indicates some of the areas where it has been employed successfully.
Auger Spectroscopy Study on the Surface Composition of Copper–Nickel Alloys after Annealing and Sputtering
Authors: Nakayama Katsuya , Ono Masatoshi , Shimizu Hazime
Published: July 2002

The changes in surface composition of Cu–Ni alloys after various treatments have been observed by means of Auger electron spectroscopy. A retarding field analyzer consisting of four spherical grids was used. Samples of six different compositions were examined to obtain the calibration curve between the chemical composition and the peak-to-peak height of the derivative Auger peak. The sample surfaces were only polished with emery papers and rinsed in water and acetone. The apparatus was ion pumped to the mid 10−9-Torr range without baking so as not to affect the samples by heating. It was found that the Ni content on the sample surfaces for 80% Ni alloy decreases during the annealing process above 100 °C; and sputtering with argon ions of about 500 eV causes the nickel to become enriched in the surface layers. A slight increase of the nickel was observed on the surface of 38% Ni alloy after initial heating.
Chemical Shifts in the Auger Spectrum of Yttrium on Oxygen Adsorption
Authors: Baker J. M. , McNatt J. L.
Published: July 2002

Adsorption of monolayer amounts of oxygen on yttrium films and molybdenum foil was studied with Auger electron spectroscopy. Exposure of yttrium to 0.3–15×10−6 Torr sec of oxygen resulted in the growth of new Auger peaks shifted by about −4 eV from the yttrium metal peaks involving the 4p, 4d, and valence levels. For molybdenum these levels were unaffected by oxygen adsorption. A background correction technique was applied in order to remove the effects of secondary electron emission from the data. The growth of the shifted peaks is followed in the spectra and the results are discussed in terms of the electronic structure of the metal and its oxide.
A magnetic sector atom-probe FIM
Authors: Müller Erwin W. , Sakurai Toshio
Published: July 2002

The 60 ° magnetic sector atom-probe field ion microscope displays a section of the momentum spectrum on a stack of microchannel plates and a proximity-focused phosphor screen. A mass resolution ΔM / M ∼ 1/2000 is achieved, and “spectral lines” made up of a few individual ions may be used for the detection and identification of products of field evaporation of metals and their compounds with adsorbate gases. The capability of the new instrument is complementary to the established ToF atom probe as it employs very low evaporation rates in slow pulse or dc field evaporation, and displays the energy distribution of field ions. As an example of the difference, a palladium–neon ion compound PdNe+ is demonstrated to be very abundant, while it is a rare species in the ToF atom probe.
Simulation of Relativistic Electron Beam Diodes
Authors: Poukey J. W. , Freeman J. R. , Yonas G.
Published: July 2002

Program DISIC, a new diode simulation code, has been developed to study the behavior of high ν/γ diodes. The code is based on a two-dimensional finite-size particle simulation model, and is designed to provide good resolution of small anode-cathode gaps. Results are shown which (i) compare with earlier calculations, (ii) compute electron trajectories in strongly self-pinched diodes, and (iii) compute electron trajectories for a diode having a conical cross section.
A New High-Resolution Electron Probe
Authors: Broers A. N.
Published: July 2002

A new high-resolution electron probe has been built for scanning microscopy studies. The probe has a final lens with a focal length of 0.8 mm, a spherical aberration coefficient; of 0.4 mm, and a chromatic aberration coefficient of 0.5 mm. A lanthanum hexaboride cathode is employed with a maximum brightness of 1.5×107 A/cm2 sr at 75 kV. The cathode operates satisfactorily at a pressure of 10−6 mm Hg. The theoretical minimum beam size for the instrument is 5 Å. Transmission scanning electron micrographs with a beam current of 1×10−12–3×1012 A indicates that close to this value is obtained in practice.
Electrical interface barriers
Authors: McGill T. C. , Mead C. A.
Published: July 2002

A review of the phenomena associated with electrical barriers between metals, and insulators and semiconductors is presented. The observed phenomenological rules governing the value of the barrier energies for different metals on the same insulator or semiconductor are presented. The barrier energies on ionic insulators are shown to vary strongly with the metal. While in the case of covalent semiconductors, the barrier energies are relatively independent of the metal. The barrier energy from the metal to the conduction band of the semiconductor is shown to be approximately two-thirds of the semiconductor band gap with certain exceptions. Transport through interfacial barriers is illustrated by discussing the transport through metal–GaSe–metal structures and Mg–SiO2 structures. Both thermal induced transport over the barrier and tunneling through the barriers are discussed.
Composition profile of ion-plated Au film on Cu analyzed by AES and SIMS during Xe ion bombardment
Authors: Narusawa Tadashi , Komiya Souji
Published: July 2002

An ion-plated 7-μ thick Au film on a Cu sheet was prepared by using a conventional ion-pumped system with 10−2 Torr of back-filled argon. The film was sputter etched at a rate of 0.5 Å/sec by 1-keV, 12-μA/ cm2 Xe ions. Sputtered species were anlyzed by a quadrupole mass spectrometer (QMS), while a cylindrical mirror Auger electron analyzer was producing spectra of the surface. The simultaneous observation was carried out throughout the sputter etching from the 7-μ-thick Au film to the bare Cu surface. Na and K ions were the predominant peaks in the observed secondary ion mass spectra (SIMS), whereas these species were less evident in the Auger spectra. Calibration for Na peaks for both spectrometers were made. Two plausible sources of these alkali species are (i) contributions from the peripheral area of ion bombardment and (ii) impurities produced in the proximity of the ion gun. Experiments reveal that the extent of Na impurities from (i) and (ii) are separated in the interpretation of the SIMS profile; for example, they are 3.7×10−9 and 1.8×10−9 A, respectively, at the average depth of 1 μ, while the current expected from the calibration is 2.5×10−9 A as AES gives 0.5% of monolayer of Na in the same depth. A full in-depth composition profile shows that impurities segregate in the top 3-μ layer and in the interface.
Trace-element effects in vacuum-melted superalloys
Authors: Kent William B.
Published: July 2002

The effects of lead, bismuth, silver, and selenium additions (at three levels each) on the workability and mechanical properties of Unitemp 718 are reported. Findings of this study include: (i) no significant effects on room temperature or 1200 °F tensile or yield strength were observed; (ii) 1200 °F stress rupture lives, and stress rupture and tensile ductilities decreased sharply with increasing content of all four trace elements: (iii) only selenium additions had a detrimental effect on workability. The lack of correlation of analytical data among laboratories noted in this study underscores the need to improve the reliability and reproducibility of analytical data through the establishment of standards for trace elements analyses.
Space-related composite-material experiments
Authors: Kaye S.
Published: July 2002

The preparation of composites in space depends on the immersion of reinforcements in a liquid-metal matrix and their uniform, stable dispersion in the bulk products until solidification occurs. The chief problem in achieving the composite is associated with the “wetting” of the reinforcements. A study of the theory of wetting revealed that wetting is prevented by the presence of gaseous and oxide contaminants at the interface between the pure liquid and pure solid. Experiment then confirmed that the use of a vacuum environment, cleaning of all surfaces, elevated temperature, ion bombardment, and vigorous mechanical agitation enabled the immersion and dispersion of candidate reinforcements. The technique is limited by the increased tendency for reaction if the time at elevated temperature is extended.
Single-source evaporation of gadolinium-cobalt alloys
Authors: Taylor R. C.
Published: July 2002

A study was made of the feasibility of using single-source electron gun evaporation for the preparation of amorphous Gd-Co alloy films. The sources used covered the compositional range from Gd0.20Co0.80 to Gd0.60Co0.40. The films deposited from each source were analyzed and the results compared with those expected for ideal alloys based on calculations using Raoult's law and Langmuir's equation. It was found that real alloys gave films with compositional gradients more than twice as severe as would be expected from ideal alloy calculations. In order to obtain films with compositional variations of one percent or less, the evaporation must consume no more than one percent of the source material.
Advances in arrayed microcolumn lithography
Authors: Muray L. P. , Spallas J. P. , Stebler C. , Lee K. , Mankos M. , Hsu Y. , Gmur M. , Chang T. H. P.
Published: July 2002

A microcolumn array has been designed, fabricated, and tested. The 2×2 array has a 2 cm pitch and operates at 1 keV. Key components include vertical interconnects, silicon low-distortion octupole deflectors, miniature long-range flexure-based tip positioners, and low-power thermal field emitters. Initial results show no observable crosstalk between columns during simultaneous operation at a 50 MHz beam blanking rate. Preliminary lithography results are presented.
Epitaxial TiN(001) Grown and Analyzed In situ by XPS and UPS. II. Analysis of Ar+ Sputter Etched Layers
Authors: Haasch R. T. , Lee T. -Y. , Gall D. , Greene J. E. , Petrov I.
Published: July 2002

X-ray and ultraviolet photoelectron spectroscopies (XPS and UPS) were used to study epitaxial TiN(001) layers grown in situ which were Ar+ sputter etched. The films were deposited on MgO(001) at 850 °C in pure N2 discharges maintained at a pressure of 5 mTorr (0.67 Pa) and shown to have a N/Ti ratio of 1.02 ± 0.02 by Rutherford backscattering spectroscopy (RBS). The films were sputter etched with 3 keV Ar+ at an angle of 40° to a constant nitrogen-to-titanium ratio. A Mg Kα x-ray source was used to obtain the XPS data, while the UPS data was generated by He I and He II radiation. The sputter etched films were found to have a N/Ti ratio of 0.73, indicating a preferential removal of nitrogen.
Spectral plasma temperature determination of thermionic vacuum arc in the titanium vapors
Authors: Biloiu Costel , Ehrich Horst , Musa Geavit
Published: July 2002

The titanium vapor plasma generated by a thermionic vacuum arc was spectroscopically investigated. The electronic temperature was obtained using the method of spectral lines intensity ratios. Three sets of spectral lines have been used, each set having the same energetic lower level namely: fundamental, 170.132 cm−1 and 386.874 cm−1 respectively. For an arc current Iarc=1 A and an arc voltage Uarc=670 V, an average electronic temperature of plasma Te=(2860±587) K was obtained. Moreover, spectroscopic investigations of the interelectrodic plasma show that the discharge is totally sustained by evaporated anode material.
Plasma treatment of polycarbonate for improved adhesion
Authors: Hofrichter A. , Bulkin P. , Drévillon B.
Published: July 2002

The deposition of silicon alloys for protective and optical coatings on polymers is of increasing interest. The understanding of the plasma polymer interaction is of prime importance here. In this work, we report a study of the influence of N2, H2, and O2 plasma treatments on pure and commercial grade polycarbonate (PC) in order to enhance the adhesion of plasma deposited silica films. Treatments and depositions were carried out in a low pressure (1 mTorr range) integrated distributed 2.45 GHz microwave electron cyclotron resonance reactor, which allows the deposition of dense stoechiometric silica at room temperature. The plasma–polymer interaction is studied by in situ UV-visible spectroscopic ellipsometry on thin spin-coated PC films. The absorption in the PC layer was found to increase in the UV which was attributed to the different reaction products of photo-Fries rearrangements, especially for pure PC. Gel permeation chromatography measurements showed that the major influence of plasma treatment on pure polycarbonate is chain scission opposed to crosslinking in the case of commercial grade PC, indicating that additives present in commercial grade PC play a major role in the crosslinking mechanisms. The plasma treatment modifies the top 330 nm/homogeneously and no indication of a high index surface layer (50–200 nm) or gradient was found. This is attributed to the low pressure of the plasma treatment, which makes a redeposition of volatile organic species unlikely.
Spectra characterization of silicon carbonitride thin films by reactive radio frequency sputtering
Authors: Peng Xiaofeng , Song Lixin , Le Jun , Hu Xingfang
Published: July 2002

Silicon carbonitride thin films were synthesized on single-crystal Si(100) substrates by reactive rf sputtering a SiC target in nitrogen and argon mixture gas (1:4) and a Si3N4 target in methane and argon mixture gas (1:5 and 1:8), respectively. The effect of target voltage on chemical composition and bonding configuration of thin films were studied. Auger electron spectra confirmed the presence of Si, C, N, and O elements in the deposited films. With the assumption that the absorption coefficient of each band was constant within the range of the film composition in question, Fourier-transform infrared spectra measurement showed qualitatively the dependence of the bonding configuration on the plasma energy. X-ray photoelectron spectroscopy analysis showed the formation of a complex network among Si, C, and N elements with more complicated atomic chemical environments than that in a mixture of pure phases, a clear correlation of binding energy and intensity of fitted features of Si 2p, C 1s, N 1s, and O 1s peaks on the target voltage. Spectra analysis reflected that the incorporation of carbon into silicon nitride and the tetrahedral carbon species (sp3 including C–C and C–N species) was enhanced by increasing the target voltage. The results demonstrated that the bonding configuration and chemical composition could be tailored by adjusting the plasma energy.
Towards the understanding of mechanical properties of super- and ultrahard nanocomposites
Authors: Veprek Stan , Argon Ali S.
Published: July 2002

This article presents an attempt to explain in a simple way, understandable to a broad spectrum of readers, the unusual combination of the mechanical properties of the recently developed new class of superhard nanocomposites, such as high hardness which significantly exceeds that of the rule of mixtures, enhancement of the elastic modulus as measured by the indentation technique, very high elastic recovery which is observed upon the indentation and the absence of crack formation even under elastic deformation corresponding to a strain of more than 10%. Future experimental work is suggested which should bring further progress towards the understanding of these materials.
Investigation of Si doping and impurity incorporation dependence on the polarity of GaN by molecular beam epitaxy
Authors: Ng H. M. , Cho A. Y.
Published: July 2002

We have investigated the growth of Ga-polarity (0001) and N-polarity (0001̄) Si-doped GaN on c-plane sapphire substrates by plasma-assisted molecular beam epitaxy. For a given Si effusion cell temperature and under similar growth conditions, the Hall carrier concentration was found to be consistently higher for samples with N polarity. Secondary ion mass spectrometry measurements show no significant difference for the incorporation of Si into GaN of either polarity. However, the incorporation of background impurities, C and O, was found to be higher for the (0001̄) GaN samples.
Vacuum Breakdown in the Presence of Thermionic Cathodes
Authors: Brodie I.
Published: July 2002

Experimental studies of field emission and breakdown with nickel electrodes contaminated by the presence of barium oxide and barium dispenser thermionic cathodes are presented. By comparing field emission and breakdown characteristics in a planar diode system and a cylindrical projection tube, it is demonstrated that minute quantities of material evaporating from the thermionic cathodes activate the tips of already existing whiskers on the nickel thus making them field emit more profusely. Breakdown is apparently caused by whisker disruption which can now occur at lower fields than that to which the surface had previously been conditioned. It is also possible that the new whiskers are formed by preferential condensation of the evaporation products. The areas from which electrons are emitted from the whisker tips usually contain only a few atoms and the regions from which electrons stream from the solid into the vacuum can be resolved in many of the electron images formed on the screen.
Single Crystal Silicon Epitaxy on Foreign Substrates
Authors: Miller Arnold , Manasevit Harold M.
Published: July 2002

Single crystal silicon has been grown epitaxially on a number of single crystal oxide substrates by chemical vapor deposition techniques. Such growth has been obtained in large area single crystal form on α-alumina, spinel, and beryllia. The distinct orientation relationships between the silicon deposits and a multiplicity of crystallographic planes of the various insulating substrates are indicated. Compatible with the earlier observed growths of single crystal tungsten on α-alumina, a model which assumes a fit between the silicon and the metal ion sites in the oxide substrate can account for all the epitaxial geometries. A concept of multiple fits in the metal-oxide system in terms of integral lattice parameter values as a guide in substrate selection is suggested. Representative electronic properties of the films and model fabricated devices, as well as a measure of their consequence in microelectronics, are given.
Detection of the Vibrational States of Gases Adsorbed on Tungsten by Low-Energy Electron Scattering
Authors: Propst Franklin M. , Piper Thomas C.
Published: July 2002

An electron spectrometer has been constructed, which is capable of detecting the vibrational states of gases adsorbed on solid surfaces. It has been found that the excitation of fundamental, harmonic, and combination frequencies can be detected with this instrument. The vibrational spectra due to the adsorption of H2, N2, CO, and H2O on the (100) surface of tungsten have been observed. A number of conclusions concerning the adsorbed state of these gases can be drawn from these spectra. These spectra and conclusions are presented and discussed. A brief description of the apparatus is also included.
Structural and Electrical Properties of Vanadium Dioxide Thin Films
Authors: Rozgonyi G. A. , Hensler D. H.
Published: July 2002

Reactively sputtered vanadium dioxide films have been analyzed to determine the relation between their electrical and structural properties. The structure of the thin films was determined by x-ray diffraction, reflection electron diffraction, and electron microscopy of carbon replicas of the film surfaces. The various substrates which were evaluated for thin film VO2 deposition were amorphous glass, glazed ceramic, and single-crystal sapphire and rutile. Electrical conductivity measurements were made to correlate film perfection with the conductivity ratio between the semiconducting and metallic states. Films deposited on amorphous substrates such as glass and glazed ceramic are polycrystalline in structure with small grain size. Conductivity ratios of approximately 102 were observed with a very broad transition region centered at 68 °C. These films, in addition to VO2, exhibit an extra x-ray line at d = 2.25, tentatively identified as VO1.87. On sapphire substrates, highly textured films were obtained while the films deposited on rutile substrates were epitaxial. In both cases conductivity ratios of 3.5 × 103 were observed. While the epitaxial films had better structural perfection, the conductivity ratio was no better than the textured films. A large grain size is considered to be the dominant factor in achieving high conductivity ratios in these VO2 films.
Preparation and Superconducting Properties of Thin Films of Transition Metal Interstitial Compounds
Authors: Gavaler J. R. , Hulm J. K. , Janocko M. A. , Jones C. K.
Published: July 2002

The importance of geometrical parameters in determining the superconducting properties of a material has recently been a topic of considerable theoretical interest. Experimental investigation in this area so far has been restricted principally to thin-film structures of the non-transition elements, compared of materials possessing relatively small superconducting non-parameters (K). In this paper we discuss some recent studies on thin-film structures of transition metal compounds having both high critical temperatures (Tc≳14 °K) and large upper critical fields (Hc2≳100 kOe). The materials in this work have the rocksalt structure (B1) and are based upon the compound niobium nitride, NbN. The films were prepared by reactive sputtering in argon-nitrogen atmospheres in an ultrahigh vacuum system with a background pressure ≲5×10−10 Torr. Variation of the nitrogen partial pressure over the range 10−3 to 10−6 Torr was used to obtain different film compositions.
Sputtered Silicon–Chromium Resistive Films
Authors: Waits Robert K.
Published: July 2002

The resistivity, temperature coefficient of resistance (TCR), and structure of annealed films deposited by de diode sputtering have been studied as a function of chromium content over the range 17–33 at.% Cr. The resistivity decreases from 0.1 to 0.001 Ω cm and the TCR changes from −1500 to +500 ppm/°C with increasing Cr content. Films containing about 27 at.% Cr had the lowest TCR. Films deposited at a cathode potential of 10 kV have a more positive TCR for the same resistivity than films sputtered at 2.5 kV. Electron micrographs showed the latter films to have a coarser structure—due either to a larger grain size (150 Ă compared to 50 Å) or to a clumping of grains. Electron diffraction patterns indicated a nearly amorphous film; CrSi2 was the only identifiable phase. The average drift of 50 μm-wide resistors (1 to 25 kΩ/square) during 1800 h at 200 °C (no load) or 125 °C (50 V dc) was ±0.5% after an initial 200 h aging under the same conditions.
Synchrotron radiation as a new tool within photon-beam technology
Authors: Doniach S. , Lindau I. , Spicer W. E. , Winick H.
Published: July 2002

Synchrotron radiation is now playing an increasingly important role in recent developments of new light sources. Synchrotron light emitted from a relativistic electron beam has a radiation pattern which makes it a unique source. The advantages with this type of radiation can be summarized as (a) continuous spectrum extending from the ir to the x-ray region, (b) strongly polarized, (c) highly collimated, (d) pulsed structure allowing time-resolution spectroscopy, and (e) high intensity making feasible the use of monochromators with narrow band pass. The Stanford Synchrotron Radiation Project has been in operation since May 1974 as a U.S. National Facility for uv and x-ray research in many disciplines using the radiation from the storage ring SPEAR at the Stanford Linear Accelerator Center. The radiation spectrum is characterized by the critical energy which varies as E3 (E=electron-beam energy) and is 11 keV for E=4 GeV. Useful flux is available out for approximately five times the critical energy. Five monochromators now share the beam run and cover the entire wavelength region from the visible to the hard x-ray region. Several experimental groups are involved in research programs including (a) uv and x-ray photoelectron spectroscopy, (b) optical reflectance and transmission studies, (c) soft x-ray absorption and extended x-ray absorption fine structure (EXAFS) studies, (d) low-angle scattering studies of certain biological materials, and (e) x-ray diffraction studies of protein crystals and other materials.
Advances in matrix-lens technology
Authors: Parks H. G. , Hughes W. C.
Published: July 2002

Recent improvements in matrix-lens technology are reported in this paper. Previously, the lenslets have been of the three-aperture einzel construction. An extensive computer study of three-aperture einzel and two-aperture immersion lenses has been made at the General Electric Research and Development Center. Calculations, based on data from this study, demonstrate significant electron-optical advantages for two-aperture immersion lenslets as opposed to three-aperture einzel lenslets. Experimental data verifying the two-aperture immersion- lenslet operation are presented. Application of the two-aperture immersion matrix lens in a sealed tube environment is also presented and discussed.
Secondary-emission electron gun for high pressure molecular lasers
Authors: Pigache D. , Fournier G.
Published: July 2002

A new type of high voltage, large area electron gun is described. Ions are generated in a low pressure ion source, extracted by a grid, and accelerated by a −130-kV continuously biased electrode. By secondary emission, these ions produce electrons which are accelerated toward the grid. They go through the ion source and an electron window (15×5 cm). Electron-beam density profiles display a good uniformity. The current density, limited only by the available power for the discharge, reaches presently 1 mA/cm2. The advantages of this gun over others are moderate vacuum requirements and capability for both low current cw and high current pulsed beams with easy control at ground potential and small energy requirement.
Fabrication of a miniature 8K-bit memory chip using electron-beam exposure
Authors: Yu H. N. , Dennard R. H. , Chang T. H. P. , Osburn C. M. , Dilonardo V. , Luhn H. E.
Published: July 2002

A fully-ion-implanted miniature 8192-bit random-access memory chip has been fabricated using electron-beam lithography with minimum linewidth between 1 and 1.5 μm and advanced Si FET technology. Device structure, processing steps, mask transfer, and reactive ion etching processes capable of fabricating device structures in the micrometer and submicrometer dimensions are described. With a minimum linewidth of 1.25 μm, the memory chip occupies an area of 1.1×1.6 mm with an array density of 5 million bits/in.2 (0.8 million bits/cm2). A typical readout access time of 90 ns was measured on a functional chip.
Optimized source for x-ray lithography of small area devices
Authors: Sullivan Paul A. , McCoy John H.
Published: July 2002

The design and performance of an optimized soft-x-ray source using an air-cooled Al target are described in this paper. The technical considerations leading to the choice of mask material, source wavelength, vacuum enclosure, and electron optics are also described. Although the authors have previously shown the need for large, powerful x-ray sources, the source described here is intended for exposure of small-area surface-acoustic-wave (SAW) devices with submicrometer dimensions. Since distortion over large areas need not be controlled, the x-ray source is limited to 1 mm in diameter and the electron beam power to 250 W. A 25-μm-thick Be vacuum window was developed which made it possible to use the Al Kα x-ray wavelength with a thin Si mask and yet maintain the exposure area in He at atmospheric pressure. The custom-designed electron gun, exposure monitor, and thermal control system are also described. Results are reported on the replication of a SAW device pattern in PMMA resist with 0.5-μm linewidths.
Channeling ion implantation through palladium films
Authors: Ishiwara Hiroshi , Furukawa Seijiro
Published: July 2002

The possibility of channeling ion implantation into semiconductors through polycrystalline metallic layers is studied. Minimum values and standard deviations of channeling angular yield in polycrystalline Pd2Si layers formed on Si have been measured by protons and 4He, and 14N ion backscattering and channeling measurements. Depth distributions of the spread of crystallite orientations and scattering centers such as lattice defects have been separately derived by using the above two quantities. It has been concluded that the channeling-ion-implantation technique will become a practical one by using the parallel scanning system.
Fabrication of lateral doping profiles by a computer-controlled focused ion beam
Authors: Seliger R. L. , Ward J. W.
Published: July 2002

The advantages and throughput of a specialized focused-ion-beam technique—the creation of smoothly varying lateral doping profiles—are investigated. Calculated and experimental results are presented for the technique by which the log(gain) –gate-voltage characteristic of a GaAs FET can be linearized over four orders of magnitude. The throughput of the lateral tailoring process is estimated to exceed 1000 devices per hour based on the assumptions of a 10-mil2 (640-μm2) area per device, an average tailoring dose of 1012 ions/cm2 for a 5-μm-diam focused spot, an ion beam brightness of ∠50 A cm-2 sr for dopant ions at typical implantation voltages 50–150 kV, and a total overhead (i.e., positioning and registration) time of 1 sec per device. While a focused ion beam system with these capabilities will require development, the performance requirements including the ion-source brightness are well within the scope of present technology.
The permeation and diffusion of hydrogen and deuterium through Rodar, tin−coated Rodar, and solder−coated Rodar
Authors: Begeal D. R.
Published: July 2002

The permeation and diffusion of H2 and D2 through Rodar (an Fe−Ni−Co alloy), and the permeation of D2 through Niromet−42 (an Fe−Ni alloy) have been measured by a membrane permeation technique. In the range of 180−550°C, the coefficients for Rodar are: KH2 = 4.9×10−3 exp(−13500/RT) cm3 (STP) sec−1 cm−1 atm−1/2, DH2 = 6.3×10−3 exp(−11100/RT) cm2 sec−1, KD2 = 4.8×10−3 exp(−13900/RT), DD2 = 2.6×10−3 exp(−10300/RT), and for Niromet KD2 = 3.4×10−3 exp(−13600/RT), where R = 1.987 cal mole−1 deg−1. Deuterium permeability measurements indicate that coatings of tin or tin−lead solder are very effective permeation barriers. At temperatures below 170°C, either coating has a permeability that is approximately five orders of magnitude less than an equivalent thickness of Rodar. However, conventional application of solder with an organic flux will injet ∠5×10−4 cm3 (STP) of hydrogen/cm2 of soldered Rodar. Dependent on the thermal environment, the injected hydrogen can diffuse through the Rodar and react with available oxygen to form water.
Growth of MgO from the vapor phase onto single−crystal metal substrate
Authors: Aboelfotoh M. O.
Published: July 2002

The growth of MgO films (∠30−4000 Å) deposited from the vapor phase on atomically smooth (111) surfaces of silver single−crystal film substrates has been studied by reflection high−energy electron diffraction. At substrate temperatures between 30 and 150°C, thin films (∠30 Å) are oriented with their (111) planes parallel to the (111) silver surface and with the [11̄10] and [̄110] MgO directions parallel to the [11̄0] silver direction. At and above 150−160°C, the orientation changes from a (111) plane to a (100) plane parallel to the (111) silver surface. The (100) orientation is fibrous with a preference for the [110] MgO direction to be parallel to the [11̄0̄] silver direction. The angular position of the (111) and (100) planes is consistent with best atomic matching at the interface between the deposit and substrate. As the film thickness is increased, the surface orientation changes to 1° (111) independent of substrate temperature. The axis of the (111) orientation tilts away from the substrate normal and toward the vapor beam direction at oblique vapor incidence.
Thin film formation of In2O3, TiN, and TaN by rf reactive ion plating
Authors: Murayama Yoichi
Published: July 2002

In2O3, TiN, and TaN films were prepared on glass substrates by a rf ion-plating technique. Indium, titanium, and tantalum were evaporated from evaporation sources in an oxygen or nitrogen atmosphere at a pressure on the order of 10−4 Torr. These films were observed to be pinhole free and uniform, showing excellent electrical and physical properties. The rf ion-plating system appears to have some advantages over other methods of reactive deposition.
Microstructure of ZnO films used for acoustic surface-wave generation
Authors: Hickernell Fred S.
Published: July 2002

Zinc oxide, vacuum deposited as a crystalline aggregate with preferential orientation of its fiber grains, has been used extensively as a film transducer for generating micro-acoustic waves. The orientation and size of the crystallite grains have a pronounced effect on the film’s electromechanical properties. The microstructure of dc-triode compound sputtered ZnO films was investigated using the analytical tools of scanning electron microscopy (SEM), reflection electron diffraction (RED), and x-ray diffraction (XRD). The ZnO films investigated had been deposited on fused quartz and oxidized silicon having surface interdigital electrode arrays from which the acoustic surface-wave properties of coupling efficiency, velocity, and propagation loss had been determined. Optically clear films having electromechanical and propagation properties approaching those of single-crystal zinc-oxide layers were found to have a smooth surface, a dense, amorphous-like vertical structure, an average crystallite size estimated at 110 Å, and a c-axis normal orientation of the crystallites to within ±5 °. Deviations from these microstructural conditions evident at the upper surface of the film layer reduced the coupling efficiency and increased the propagation loss. The major microstructural manifestation was a roughened surface giving the film a cloudy optical appearance. Only minor deviations in the average orientation and grain size of the crystallites were evident.
Properties of sputtered high Tc thin films
Authors: Gavaler J. R.
Published: July 2002

Of all of the presently known superconducting materials, only a few have critical temperatures (Tc) of 15 K or higher. We have been investigating the properties of sputtered thin films of several of these highest Tc materials, including Nb3Ge, NbN, Mo−Re, Nb−Sn, and Nb−Ga, among others. It has been found that these films occasionally have enhanced Tc compared to bulk samples. Most notable of these are Nb3Ge films which have the highest presently known Tc (∠23 K). In addition, the sputtered films often exhibit superior current and magnetic field characteristics. All of these thin film results are reviewed together with x−ray and electron microscope results, which indicate that the enhanced properties of the films are due to both structural and compositional differences between thin film and bulk samples.
Glow discharge optical spectroscopy as an analytical depth profiling technique
Authors: Greene J. E. , Sequeda−Osorio F. , Natarajan B. R.
Published: July 2002

Glow discharge optical spectroscopy has been demonstrated to be capable of obtaining chemical composition vs depth information in microvolume solid samples. Sample geometry and sputtering pressure were found to have a large effect on measured multilayer interface sharpness. The use of a sample backing plate which has a similar electrical conductivity and a larger cross−sectional area than the sample to be analyzed was found to greatly increase the interface depth resolution. Results are presented for GDOS−determined boron implantation and phosphorus diffusion profiles in Si. The measured profiles appear somewhat broader than expected from theory and possible explanations for this discrepancy are discussed.
Dielectric instability and breakdown in wide bandgap insulators
Authors: DiStefano T. H. , Shatzkes M.
Published: July 2002

An impact−ionization model predicts a negative resistance type of dielectric instability and breakdown in wide bandgap insulators. The instability develops by the injection of electrons from the cathode, impact ionization of the lattice, and a distortion of the electric field which leads to a further increase in impact ionization. For the case of thin films, it is necessary to invoke a nonlocal ionization rate in order to obtain a negative resistance instability. O’Dwyer’s avalanche theory of breakdown, which applies well to semiconductors, cannot be used to predict a negative resistance in the small multiplication limit appropriate to wide bandgap insulators. The impact−ionization model presented here depends upon two critical parameters: the ionization bandgap of the material and the electron−LO phonon scattering length. Evaluated for the exemplary case of SiO2, the model predicts a current density and an average field at breakdown which increase rapidly for film thickness below 200 Å.
Graphite surface erosion and blistering
Authors: Feinberg Benedict , Post Richard S.
Published: July 2002

Bulk reactor-grade graphite and WCA graphite cloth were exposed to an atom and ion beam produced in a Hall accelerator. Samples exposed to hydrogen received a total dose of 1020 atoms/cm2 of 580-eV mean energy H0 and 5×1018 ions/cm2 of 875-eV mean energy H+. Samples exposed to helium received a total dose of 1020 atoms/cm2 of He0 and 5×1018 ions/cm2 of He+. During irradiation, the pressure in the sample region was governed by the partial pressure of the source gas (H2or He) and was at 47 mPa. The samples were then examined with a scanning electron microscope and an optical interference microscope to determine the surface damage. Upon exposure to H0 and H+, the bulk graphite and the graphite cloth samples showed substantial surface erosion. The amount of erosion was found to be strongly dependent on the sample surface temperature. Upon exposure to He+, blistering was observed on the graphite cloth sample. No measurable surface erosion of the samples exposed to He was observed with the scanning electron microscope.
Abstract: Electrical characteristics of the InP surface
Authors: Lile D. L. , Collins D. A.
Published: July 2002

ed barnas to delete on disk material may exhibit improved transferred electron device performance.
Variation of Schottky-barrier energy with interdiffusion in Au and Ni/Au–Ge films on GaAs
Authors: Robinson G. Y.
Published: July 2002

The results of an experimental study of the interdiffusion occurring at elevated temperatures in Au/GaAs and Ni/Au–Ge/GaAs thin-film systems and of the corresponding changes in the Schottky barrier energy φBn are presented. Composition-depth profiles obtained with Auger electron spectroscopy and in situ sputter etching are used to observe the interdiffusion behavior. For Au/GaAs samples, significant Ga outdiffusion and surface accumulation is found along with appreciable lowering of φBn with increasing heat treatment. For an ohmic contact consisting of Ni/Au–Ge/GaAs, Ni moves through the Au–Ge layer to produce an increase in φBn at temperatures below the Au–Ge eutectic point. Considerable intermixing of all constituents of the Ni/Au–Ge/GaAs system is found to occur above the Au–Ge eutectic temperature.
Target heating during ion implantation
Authors: Parry Peter D.
Published: July 2002

The temperature of ion-implanted silicon wafers has been measured as a function of time using an infrared pyrometer. Ion beam power density was varied from 0.10 to 200 W cm−2, and the target temperature was measured in the range from 100 °C to the silicon melting point. The resulting heating and cooling curves have been analyzed using a model which includes the effects of ion beam heating, radiative cooling, conductive cooling, and reradiation from the surroundings. For the system studied, conductive cooling in vacuum is less reliable and generally less effective than radiative cooling, unless conductive grease can be used. The model has also been generalized to the case of a group of wafers being scanned cyclically by the ion beam, and the calculated temperatures have been compared with experimentally measured values. Implanting N wafers cyclically is not equivalent to dividing the input power density by N, because the time required for the wafers to cool is typically less than the time between scans. However, it is possible to reduce the wafer temperature by many hundreds of degrees by choosing the scan rates properly. The model is intended as a guide to the design of new apparatus as well as to the use of existing ion implantation systems. Although silicon is used in the examples, the procedure can easily be generalized to other target materials.
Study of calcia-stabilized zirconia thin-film sensors
Authors: Croset M. , Schnell P. , Velasco G. , Siejka J.
Published: July 2002

The ionic transference number of rf-sputtered calcia-stabilized zirconia (CSZ) thin films has been investigated, using the Nernst method, in the 300 °–400 °C temperature range and between 10−4 and 2×10−1 atm of oxygen partial pressure. E.M.F. measurements at 342 °C on Ni–NiO/CSZ/Pt–O2 galvanic cells show a voltage roughly 5% lower than the theoretical value and an ionic transference number of about 0.85. Possibilities of such cells being used as oxygen sensors were estimated. Rise times typically observed between 10−3 and 10−2 atm of oxygen were approximately 4 min at 280 °C and 5 s at 420 °C. The influence of Pt deposition parameters on the response speed is pointed out.
Auger analysis of the anodic oxide/InP interface
Authors: Wilmsen C. W. , Kee R. W.
Published: July 2002

Auger line shape, energy shifts, and profiling techniques have been used to analyze the anodic oxide/InP interface. The composition and bonding of oxides grown in either 0.1 N KOH or 3% tartaric acid/propylene glycol electrolytes were investigated. Plots of the P(KL2L2) and the In(M4,5N4,5N4,5) line shapes provided useful information in determining the boundaries between predominately In–O/In–P and P–O/P–In bonding. The oxides were determined to have an outer layer of a mixture of In and P oxides. The transition from In–O bonding to In–P bonding for the tartaric acid-grown oxide occurred over a greater thickness than for the KOH-grown oxide. The P–O to P–In bonding transition occurred over approximately the same thickness for both oxides.
Surface segregation of Sn during MBE of n-type GaAs established by SIMS and AES
Authors: Ploog K. , Fischer A.
Published: July 2002

Auger electron spectroscopy (AES) and secondary ion mass spectroscopy (SIMS) have been used to study in situ the surface segregation of Sn, which occurred during molecular-beam epitaxy (MBE) of Sn-doped GaAs films. With both surface diagnostic techniques, a significant amount of Sn, about three orders of magnitude larger than the portion being incorporated into the growing film was detected in the outermost atomic layers (∠10–20 Å thick) of the prepared film. The surface segregation of Sn started at a substrate temperature as low as 490° C and increased with temperature and−to some extent−with increasing dopant concentration. Thus, the measured doping profiles of Sn-doped GaAs layers, when grown above 490° C, deviated considerably from the ideal profile calculated from the molecular beam intensity of the dopant. The surface segregation of Sn during epitaxial growth was also found in Sn-doped GaAs films prepared by liquid-phase epitaxy (LPE) from Ga solutions.