bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Inlet Flow Field Conditions on the Performance of Centrifugal Compressor Diffusers: Part 1—Discrete-Passage Diffuser
Authors: Filipenco V. G. , Deniz S. , Johnston J. M. , Greitzer E. M. , Cumpsty N. A.
Published: July 2002

This is Part 1 of a two-part paper considering the performance of radial diffusers for use in a high-performance centrifugal compressor. Part 1 reports on discrete-passage diffusers (shown in Fig. 1) while Part 2 describes a test of a straight-channel diffuser designed for equivalent duty. Two builds of discrete-passage diffuser were tested, with 30 and 38 separate passages. Both the 30 and 38 passage diffusers investigated showed comparable range of unstalled operation and similar level of overall diffuser pressure recovery. The paper concentrates on the influence of inlet flow conditions on the pressure recovery and operating range of radial diffusers for centrifugal compressor stages. The flow conditions examined include diffuser inlet Mach number, flow angle, blockage, and axial flow nonuniformity. The investigation was carried out in a specially built test facility, designed to provide a controlled inlet flow field to the test diffusers. The facility can provide a wide range of diffuser inlet velocity profile distortion and skew with Mach numbers up to unity and flow angles of 63 to 75 deg from the radial direction. The consequences of different averaging methods for the inlet total pressure distributions, which are needed in the definition of diffuser pressure recovery coefficient for nonuniform diffuser inlet conditions, were also assessed. The overall diffuser pressure recovery coefficient, based on suitably averaged inlet total pressure, was found to correlate well with the momentum-averaged flow angle into the diffuser. Furthermore, the pressure recovery coefficient was found to be essentially independent of the axial distortion at diffuser inlet, and the Mach number, over the wide flow range (from maximum flow to the beginning of flow instabilities) investigated. It is thus shown that the generally accepted sensitivity of diffuser pressure recovery performance to inlet flow distortion and boundary layer blockage can be largely attributed to inappropriate quantification of the average dynamic pressure at diffuser inlet. Use of an inlet dynamic pressure based on availability or mass-averaging in combination with definition of inlet flow angle based on mass average of the radial and tangential velocity at diffuser inlet removes this sensitivity. [S0889-504X(00)00101-X]
Dynamic Behavior of Transportation Pressure Relief Valves Under Simulated Fire Impingement Conditions
Authors: Pierorazio A. J. , Birk A. M.
Published: July 2002

This paper presents the results of the first full test series of commercial pressure relief valves using the newly constructed Queen’s University/Transport Canada dynamic valve test facility (VTF) in Maitland, Ontario. This facility is unique among those reported in the literature in its ability to cycle the valves repeatedly and to measure the time-varying flow rates during operation. This dynamic testing provides much more insight into valve behavior than the single-pop or continuous flow tests commonly reported. The facility is additionally unique in its simulation of accident conditions as a means of measuring valve performance. Specimen valves for this series represent 20 each of three manufacturers’ design for a semi-internal 1-in. 312 psi LPG relief valve. The purpose of this paper is to present the procedure and results of these tests. No effort is made to perform in-depth analysis into the causes of the various behaviors, nor is any assessment made of the risk presented by any of the valves. [S0094-9930(00)01201-4]
Methodology for Durability Analysis of HDPE Pipe
Authors: Chudnovsky A. , Sehanobish K. , Wu S.
Published: July 2002

Toughness evaluation and durability analysis are two of the critical steps to design a toughened HDPE resin for durability in pipe applications. Durability analysis involves defect characterization, crack initiation and propagation mechanism, and long-term performance prediction. The methodology for durability analysis of high-density polyethylene (HDPE) pipe will be discussed in this paper. Various analytical techniques, such as fractography, hot-stage microscopy, energy-dispersive X-ray (EDX), microtransmittance infrared spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM), have been used to characterize the defect properties and size distribution. Crack initiation and propagation mechanisms in HDPE have been analyzed by some accelerated tests and compared with that observed in the long-term hydrostatic pressure test. A new procedure for lifetime prediction of HDPE under creep is discussed based on the crack layer theory (Chudnovsky, A., 1984, NASA Contractor Report 174634). [S0094-9930(00)00802-7]
Polybutylene Terephthalate (PBT) Spin Cast Films by XPS
Authors: Burrell Michael C. , Chera John J.
Published: July 2002

A spin cast film of poly(butylene terephthalate) (PBT) was analyzed by XPS using monochromatic Al Kα excitation. The measured atomic composition closely matched the expected stoichiometry of the polymer. Peak positions of the individual chemically shifted C 1s and O 1s components are reported. The results are in general agreement with other reported spectra of PBT polymers: experimental, C 74.8% and O 25.2%; theoretical, C 75% and O 25%.
Molecular adsorption of CH3CN and C5H5N on Si(111)7×7
Authors: Shirota N. , Yagi S. , Taniguchi M. , Hashimoto E.
Published: July 2002

The adsorption structures of CH3CN and C5H5N molecules on the Si(111)7×7 surface have been studied by a low temperature scanning tunneling microscopy. These molecular adsorption sites are across the dimer row of the Si(111)7×7 surface. These molecular adsorption structures can be explained, assuming the dipole–dipole interaction between the molecules and the Si(111)7×7 surface.
Gas utilization in remote plasma cleaning and stripping applications
Authors: Kastenmeier B. E. E. , Oehrlein G. S. , Langan John G. , Entley William R.
Published: July 2002

Nitrogen trifluoride (NF3) is a likely candidate to replace perfluorocompounds (PFCs) in stripping and reactor cleaning applications. In this article, the performance of NF3 for the etching of silicon, silicon dioxide (SiO2), and silicon nitride (Si3N4) is compared with that of CF4, C2F6, and C3F8. The performance measures emphasized in this article are the dissociation efficiency of the parent molecule in the discharge, the etch rate, and the gas utilization. The destruction efficiency of NF3 in the discharge as determined by mass spectrometry is typically 100%. The maximum destruction of the PFC gases for the parameters used in this investigation is approximately 75% for CF4, and can approach 100% for C2F6 and C3F8. The removal rates for NF3 obtained at optimum settings of O2 addition and microwave power are significantly higher than those for PFC gases. The gas utilization, which describes the degree of conversion of the parent molecules into etch products and is defined in this article, is also higher for NF3 than for the other gases investigated.
Morphological investigation of ultrathin Ag and Ti films grown on hydrogen terminated Si(111)
Authors: Gergen B. , Nienhaus H. , Weinberg W. H. , McFarland E. M.
Published: July 2002

The growth of ultrathin Ag and Ti films on hydrogen terminated Si(111) has been investigated using electrical resistance measurements and atomic force microscopy (AFM). The films were deposited by electron beam evaporation at a rate of 0.01 nm/s under ultrahigh vacuum conditions at substrate temperatures from 130 to 550 K. The films were analyzed by in situ electrical resistance measurements during deposition and annealing, and by ex situ AFM characterization. The Ag films required approximately 5.5 nm to achieve electrical continuity at a deposition temperature of 130 K, whereas the Ti was found to produce electrically continuous films after deposition of 0.5 nm at room temperature. Film resistance and AFM measurements suggested island growth for Ag and layer by layer growth for Ti. The Ag island size of 10 nm films increased from a base area of approximately 2×103–9×103 nm2 with increasing deposition temperature from 300 to 550 K. The use of a 4 nm Ti buffer layer on the Si was found to significantly decrease the final roughness of the Ag films.
Friction and wear of plasma-sprayed NiO based coatings
Authors: Moore G. David , Ritter John E.
Published: July 2002

The friction and wear characteristics of plasma-sprayed NiO–CaF2 coatings on Incomel 601 substrates were studied at 760 °C and load of 5.17×104 N/m2. The rubbing surface was a lithia alumina silicate ceramic matrix simulating a rotating heat exchanger for use in automotive gas turbines. Average friction coefficients varied from 0.28 to 0.58 with coating wear rates of 0.2 to 2.1×10−3 cm/100 h. Optimum wear performance was achieved for the prespray composition 92/8 weight % NiO/CaF2.
Soft x-ray appearance potential spectroscopy of lanthanum, gadolinium, and thorium
Authors: Murthy M. S. , Redhead P. A.
Published: July 2002

The electron binding energies of La (M2–N 5,4 levels), Gd (M3–N 5,4 levels) and Th (O5–N1 levels) were determined by SXAPS and compared with those obtained by ESCA and by calculation. The results are in reasonable agreement. The La was oxidized and the shift in the SXAPS peaks was less than 1 eV. Satellite peaks have been observed associated with the M5, M4, and N 5,4 peaks of La and Gd and the O5 and O4 peaks of Th. Possible mechanisms responsible for these satellite peaks are discussed.
Pressure Bursts in High-Vacuum Systems
Authors: Fluegge Robert A. , Huber James E.
Published: July 2002

All upward, inverted-cone extension to all oil diffusion pump cold cap appears to provide a method for reducing amplitude and frequency of pressure bursts in a continuously pumped vacuum system. Indications are that the pressure fluctuations are a result of oil dripping from the cold cap and/or the liquid nitrogen trap directly over the diffusion pump, then reevaporating and backstreaming into the vacuum system. Oil drip wires are shown as necessary to guide the condensed oil to the pump inner walls rather than into the hot vapor stream. The erratic behavior of these bursts and the difficulties in pinpointing their behavior is given in considerable detail.
Effect of Reduced Pressure Induction Melting on Short Transverse Properties of 7075 Aluminum
Authors: Inouye Shingo , Sweeney Robert A.
Published: July 2002

Vacuum degassing techniques have been successfully applied to aluminum alloys for the production of sound, high strength, shaped castings. However, the use of a low-pressure environment during the melting process has not been utilized to the authors' knowledge. This experimental study has been an attempt to combine the desirable features of induction melting, such as uniform mixing and good temperature control of the melt, with an environment of low pressure for degassing of the melt and restricting the supply of reactive gases. The study has been limited to a single high strength wrought alloy: 7075-T6 aluminum. The short transverse ductility of this material is a sensitive indicator of deficiencies in materials and processing. Therefore, emphasis has been placed on the material properties in this direction as a means of evaluating melting variables. An attempt was made to correlate melt variables, such as starting material purity, gaseous environment and oxide removal methods, with tensile properties, stress corrosion properties and endurance limit in the short transverse direction of forged material in the solution treated and aged (T6) condition. Preliminary data was presented.
Optical Constants of Opaque Semiconductors
Authors: Potter R. F.
Published: July 2002

The pseudo-Brewster angle technique for determining the optical constants of an optically isotropic medium, is reviewed and a description of a reflectometer based on this measurement technique is described in detail. Room temperature values of the optical constants of two examples have been determined: a Ge film prepared by evaporating the semiconductor onto a substrate held at 410°C, well above the substrate temperature below which amorphous-like films occur, and an epitaxial layer of Si deposited on single crystal Si. A great value of modern thin-film technology is that it offers materials prepared in a controlled manner with unique, virgin, specular surfaces of importance for optical measurements and applications.
Analysis of a Ring Cavity Thin-Film Deposition Source
Authors: Feisel Lyle D.
Published: July 2002

Equations are derived which allow the prediction of the thickness distribution of thin films deposited from sources possessing vertical sides and axial symmetry. These equations are in the form of three double integrals which must be integrated over a variable region of integration. Some correlation with experiment is also reported.
Effect of Stress on the Physical Properties of Thin Films
Authors: Klokholm Erik
Published: July 2002

Residual stresses are almost always present in thin films; the magnitude of the stress (tensile or compressive) can be as small as 107 or as large as 1010 dyn/cm2. The stress in fine-grained polycrystalline films is generally isotropic in the plane of the film, and has no stress component perpendicular to the film plane. In such films there is then an isotropic strain in the film plane with a Poisson’s strain normal to the plane. For single crystal films the strain anisotropy will depend on the orientation of the film axes with respect to the substrate. In either case these strains induce an anisotropy and changes in the physical properties of the film. As examples of the effect of stress, the changes in magnetic and superconducting transition temperatures, and the induced magnetic, resistive, and optical anisotropies will be discussed.
Measurement of the Effective Yield of Electrons from the Cathode of a Penning Discharge
Authors: Akaishi Kenya
Published: July 2002

The ejection of electrons by ions from the cathode of a modified cold-cathode Penning gauge was observed and a technique for the determination of effective ejection yield of electrons by ions is discussed. When the gauge was operated with a magnetic field of 600 G, an anode voltage of 2 kV, and at a pressure of 2.6×10−9 Torr, the average ion energy and the effective yield were, respectively, estimated to be 460 eV and 0.21.
Adsorption of Transition Metal Atoms on a Transition Metal Substrate
Authors: Cyrot-Lackmann F.
Published: July 2002

The binding energy of transition atoms adsorbed on a transition metal of the same series is studied in a tight binding model using a moment’s expansion technique. The general trends of the variation of the binding energy with the number of adatom d electrons are similar for all the substrates. As the number of d electrons is increased, they show a parabolic variation with a maximum of the order of the cohesive energy of the substrate and a sharper decrease after the maximum. These results are in good agreement with the experimental results on 5 d adatoms on tungsten. Interaction energies between adatoms are also studied and shown to be only of some importance for neighboring adatoms and rather small compared to the binding energy of a single adatom.
Experimental Investigations on Oil and Mercury Diffusion Pumps with Differing Nozzle Geometries
Authors: Fleischer W. , Szyszka S. , Müller B.
Published: July 2002

Experimental investigations with commercial oil diffusion pumps are reported, where the top nozzle of the four stage nozzle system was replaced by dual nozzles with variable throat widths. Certain changes of pumping speed characteristics could be observed when varying the heater input for different throat widths but, in general, a lower maximum pumping speed was measured for dual nozzles. Even when taking into consideration the pump fluid backstreaming the use of dual nozzles in commercial oil diffusion pumps does not show any advantages. In addition, results of measurements of the pumping speed and of the compression ratio in single-stage mercury diffusion pumps for different nozzle geometries but with identical nozzle throat areas in dependence on mass flow are reported. Here, too, the dual nozzle gave only a slight improvement in the compression ratio. The results are discussed applying familiar principles of the diffusion pump theory.
Promise of Optical Memories
Authors: Rajchman Jan A.
Published: July 2002

Holographic and various other techniques may make it possible for the first time to store billions of bits on a permanent and shelvable record so that there is full random addressing in microseconds both for recording and reading out. Such a mass optical memory, with the capacity and permanence of disks, but without any mechanical motion, and the accessibility of cores, may replace both and thereby greatly improve the performance and simplify the architecture and operation of computers. The concept is based on compounded selection, an internal electrically and light addressable matrix array, and holographic storage on an erasable and reusable continuous recording medium. The progress toward implementation of the concept and the remaining challenges will be discussed, including specific aspects of light deflection and modulation, the over-all optical system, and the storage medium.
Kinetics and Thermodynamics of the Deposition of Zinc Films on Germanium (110) and (100) Surfaces
Authors: Voorhoeve R. J. H. , Carides J. N.
Published: July 2002

The initial stages of the deposition of thin zinc films on the (110) and (100) surfaces of germanium single crystals have been studied. A mass-spectrometric molecular beam method was used in ultrahigh vacuum. The evaporation rate of the thin film was measured during depositions at various temperatures and beam intensities. On both substrates, the adcoverage approaches complete saturation of available adsorption sites before nucleation of bulk zinc starts. Nucleation therefore occurs on a composite substrate. On (110) substrates, the critical nucleation stage of thin film formation is determined by the coverage only. The thermodynamic parameters of the critical deposit, such as the equilibrium evaporation rate, the thermodynamic potential, and the differential binding energy, have been determined. These thermodynamic parameters determine the critical beam intensity necessary for nucleation. The deposition of zinc on (100) substrates is more complex. The critical nucleation state of the deposit is determined not solely by the coverage, but also by the deposition conditions of temperature and beam intensity. In such a case, thermodynamic parameters cannot be obtained by the present technique.
Relative photoelectric yields of some metal films and dielectrics in an insulated electrode discharge
Authors: Lay Frank M.
Published: July 2002

The relative photoelectric emission of some metal films and dielectrics in a glow discharge of neon and Penning mixture of neon plus argon was measured. Major portions of the photoelectric yield are caused by cathode bombardment of energetic photons with energy larger then 11 eV. Observed in the Penning mixture is a sharp decrease in photoemission as compared to that in pure neon. It is explained that the decrease is due to Penning collisions, which drains away large numbers of neon metastables.
Manganese sputter-etch masks for integrated optical circuits
Authors: Muska W. M.
Published: July 2002

The fabrication of integrated optical circuits, such as directional couplers, requires dielectric patterns of high resolution and edge acuity. This paper describes the application of manganese sputter-etch masks to the fabrication of these circuits. It is shown that the physical properties of manganese are well suited to mask fabrication by the lift-off technique and that optical waveguides sputter etched from glass films using these masks meet the stringent edge-roughness requirements for low-loss guidance. Manganese masks may also be suitable for other applications where high resolution and edge acuity are important.
Analysis of thermal-desorption spectra using a computer graphics system
Authors: Kornelsen E. V. , O'Hara D. H.
Published: July 2002

A computer graphics system has been programmed to allow experimental thermal-desorption spectra to be matched visually with the sum of up to twelve theoretical first-order desorption peaks. The system allows the resulting theoretical spectrum to be stored for later recovery or plotted along with the experimental spectrum using an X–Y plotter. The temperatures and amplitudes of the chosen theoretical peaks and the rms difference between the theoretical and experimental spectra are available for either display or printout. Analysis of a series of helium desorption spectra showed that peak temperatures could be determined to within ±0.8%, and that the main limitations were attributable to temperature uncertainties and noise in the experimental spectra.
Effects of particles on high-voltage vacuum breakdown and interelectrode current
Authors: Maley J. J.
Published: July 2002

Ten types of particles commonly found in electron tubes were tested for their effects on high-voltage breakdown and interelectrode current. The particles were applied to stainless steel electrodes and then tested for initial breakdown voltage, number of breakdowns necessary to condition the electrodes, and interelectrode current after high-voltage conditioning. It was found that insulating particles lower the breakdown voltage as much as 30% but the electrodes can be easily conditioned with little damage. Conducting particles and amorphous carbon particles lower the breakdown voltage up to 45%. In addition, these particles cause severe high-voltage conditioning problems. There is much more arcing during conditioning which results in severely damaged electrode surfaces. The arc craters are then a source of interelectrode leakage.
Magnetic Thin Films for Optical Storage
Authors: Lee Kenneth
Published: July 2002

The magneto-optical properties of magnetic materials in thin film form have been of considerable interest since thermal magnetic recording was demonstrated on MnBi. With the advances being made in materials research and laser technology, a laser addressed system may be realized. Material requirements necessary for thermal magnetic recording are discussed. A review is made of those materials whose magnetic and optical properties have been studied. By comparing the known material properties with the required properties for a laser addressed memory, this review shows that, at present, four recently discovered compounds have satisfactory properties for an optical storage system. These four are high temperature phase MnBi doped with Ti or Ni for stabilization, MnAlGe, MnGaGe, and amorphous GdCo5.
Thin Film Superconducting Devices
Authors: Mercereau J. E. , Notarys H. A.
Published: July 2002

Techniques have been developed with which it is possible to fabricate superconducting thin film structures (“bridges”) which show Josephson-like phenomena, with a wide variety of electrical and superconducting parameters. These bridges—based on the proximity effect—are made in layered thin film substrates which have been fabricated from many different, both hard and soft, superconducting materials. The fabrication techniques and the electrical and superconducting characteristics for these proximity effect bridges including a simple low frequency (≤ 10 GHz) equivalent circuit will be discussed. These bridges have been incorporated into simple thin film circuits for use as galvanometers, magnetometers, gradiometers, detector arrays, etc. Extension of these techniques to more complex superconducting thin film bridge circuits including resistors, capacitors, and inductors will be indicated.
Fluxoid Properties in Superconducting Films
Authors: SooHoo W. J. , Coren R. L.
Published: July 2002

Theoretical studies of surface proximity effects in thin film superconductors have indicated a significantly different fluxoid structure from bulk. These results have led to suggestions that the static arrangement and dynamic behavior of fluxoids in films also differ. No experimental studies of these features have been reported. For this study niobium films 100–700 Å thick were placed in one arm of a 9.5 GHz reflection bridge in a perpendicular magnetic field. The complex reflection coefficients yield complex surface impedances which can be interpreted in terms of dynamic fluxoid properties. Some suggestive features are noted.
Study of Interface Phonons in Lamellar Eutectics
Authors: Proix F. , Racek R. , Balkanski M.
Published: July 2002

Infrared quasinormal reflectivity has been measured at room temperature betweeen 200 and 700 cm−1 on lamellar eutectic mixtures LiF-NaF. The samples were cut perpendicular to the lamellae and their period was 1 or 7 μ. The difference between the experimental curves and a “theoretical” reflectivity, which is a weighted sum of the reflectivity curves of the pure compounds, is attributed to the interfaces. The difference curves exhibit five peaks, three of which are centered near bulk frequencies of the compounds. The other two are interpreted as interface modes and their frequencies compare quite well with the theory.
Bound States in Normal-Metal—Superconductor Sandwiches: Magnetic Field Dependence and Estimate of Fermi Velocities in Zinc
Authors: Rowell J. M.
Published: July 2002

The pair potential well, produced in a normal metal by proximity with a superconductor, supports bound states which can be observed in a tunneling experiment. Such states have been observed in Pb/Zn-zinc oxide-Pb, and the temperature dependence of the I–V characteristic has been reported. Here these experiments are continued, showing, in particular, the magnetic field dependence of the bound states. The dressed Fermi velocities along the c axis of zinc are estimated to range from 0.4×108 to 1.0×108 cm/sec, but to obtain improved accuracy in this measurement cleaner and thicker Zn films are required.
Four Models of Electron Distribution in the Orbitron
Authors: Deichelbohrer P. R.
Published: July 2002

As a guide to the design of orbitron pumps and gauges, the radial variation of electron number density is calculated for four models of angular and axial momentum distributions. Uniform angular momentum distribution (for fixed axial momentum) gives an almost constant density. Angular momentum distribution that varies as sin2 gives two peaks. Adding a uniform distribution of axial momentum decreases the density near the cathode such that the outer peak is removed from the two-peak model. Also, the density is approximately proportional to the electron speed near the cathode in the model with uniform distribution of angular momentum.
Coates–Kikuchi Patterns and Electron-Spectroscopy from Single Crystals
Authors: Wolf E. D. , Coane P. J.
Published: July 2002

Experimental measurements are reported on the geometric and intensity variations of Coates–Kikuchi backscattered electron images from several single crystals as a function of the primary electron beam energy and angle of beam incidence to the crystal lattice. Total energy distribution measurements of the backscattered electrons were also made on a (001) GaAs wafer using a custom designed cylindrical mirror electron analyzer. The number of elastically backscattered primary electrons decreased by 80% when the beam was incident in the off-axis direction. The first plasmon loss peak was observed at −14.5 eV ± 1 eV, with a primary beam energy of 8 keV. The motivation for this work is a better characterization of the high-contrast Coates–Kikuchi patterns that we have observed using an energy sensitive solid-state detector, and better application of these patterns, which are highly detailed reciprocal lattice displays, to surface analysis. Generation of these displays in a scanning electron microscope allows practical and rapid measurement of crystal orientation, crystal type, and near-surface lattice disorder.
Electrical and optical properties of rf triode-sputtered Au films
Authors: Cornely R. H. , Fuschillo N.
Published: July 2002

A large number of Au films with different nominal film thicknesses (NFT) from 12 to 960 Å, were rf triode sputtered with 2.5 kV in a single pumpdown in 1-mTorr argon, at a deposition rate of about 1.5 Å/sec, onto amorphous SiO2 at 120 °C. The film substructure, as determined by transmission electron microscopy, showed that the island particles became metallically connected at a NFT of about 30 Å. This small value was attributed to the high nucleation density (about 1.2×1012 nucleated particles/ cm2 at a NFT of 12.7 Å) and to the fact that the island particles grow as flattened platelets. Microscopy also revealed that the islands were composed of small single crystallites with mean dimensions less than 50 Å for a NFT of 20 Å. The surface coverage increased with NFT to about 100% at 100 Å. The mean crystallite increased to about 85 Å and then tended to remain constant for NFT's above 100 Å. The electrical resistivity of films with an NFT greater than 30 Å was measured over the temperature range 77–300 K. In the NFT range 30–40 Å, the films were found to have a very small positive temperature coefficient of resistance (TCR) that increased linearly with NFT from 0.0002 to 0;0004 K−1 and a large sheet resistance that decreased rapidly from 1000 Ω/□ (30 Å) to 100 Ω/□ (40 Å). Films greater than 100 Å had resistivities 3–4 times that reported for single-crystal Au. This increase was mainly attributed to polycrystalline grain boundary scattering. Optical properties were studied by measuring the reflectance and transmission of films over an incident wavelength range from 0.18 to 2.0 μ. Films with NFT's less than 50 Å were found to behave optically according to the Maxwell-Garnett theory for an array of particles, even though the island particles of these films were irregularly shaped. Optical indices were calculated for films thicker than 12 Å.
The application of transmission electron microscopy through the use of thin foils
Authors: Moon D. M.
Published: July 2002

Basic procedures of TEM are described, and the recent advances in the technique and in its application are reported. Among the most recent developments are: (i) high-voltage electron miscroscopy, which lessens the stringement requirement for producing foils as thin as 2000−500 A; and (ii) scanning transmission electron microscopy, which offers benefits over conventional TEM, e.g., an increase in penetrating powder by a factor of about 3, and a time-resolved image. The application of these techniques, as well as energy analysis, will become widespread as more instruments become available, enlarging further the number and types of problems capable of solution with TEM.
Abstract: Effect of pool temperature gradients on the composition of electron-beam vapor-deposited alloys
Authors: Krutenat R. C.
Published: July 2002

The common requirement of a water-cooled hearth for continuous electron-beam evaporation of alloys with a rod-fed source introduces a temperature gradient in the evaporating surface. A spatial heterogeneity of alloying constituents can be shown to result from evaporation in this gradient. Application of thermodynamic considerations to the equilibrium evaporation at constant rate from an alloy-rod-fed electron-beam vapor-deposition source provides an explanation of the spatial heterogeneity of alloy constituents in the vapor cloud. Consideration of these effects offers some direction for improved electron-beam gun/hearth design for utilization in vapor-deposition processing of complex alloys.
The effects of preadsorbed oxygen contaminant on the adsorption of Al on Si (111)
Authors: Bellina J. J.
Published: July 2002

The effects of preadsorbed oxygen on the ordering of aluminum atoms deposited upon the (111) surface of silicon single crystals were investigated by low-energy electron diffraction and Auger electron spectroscopy. The extent of ordering of the Al atoms and the orientation of the adsorbate relative to the Si lattice were determined as functions of temperature from 200 to 1000 °C. Deposition of Al upon clean Si (111) at 25 °C produced a partially ordered Al (111) adlayer, whereas deposition upon an oxygen-contaminated surface resulted in the formation of a completely disordered Al layer. Upon subsequent heating to higher temperatures, the adlayer irreversibly converted to an epitaxial (111) films. The temperature for epitaxy was higher for increased oxygen preexposure. The results indicated that this conversion was not caused by oxygen desorption or the formation of an oxide phase.
Relative work function of clean molybdenum single-crystal planes determined by field emission microscopy
Authors: Bergeret G. , Abon M. , Tardy B. , Teichner S. J.
Published: July 2002

A probe-hole field emission microscope has been used to determine the work function of clean molybdenum single crystal planes relative to the average work function of the field emitter, assumed to be 4.20 eV. Results obtained are compared with other available data. (AIP)
Characterization of additive systems for damascene Cu electroplating by the superfilling profile monitor
Authors: Chiu Shao-Yu , Shieh Jia-Min , Chang Shih-Chieh , Lin Kun-Cheng , Dai Bau-Tong , Chen Chia-Fu , Feng Ming-Shiann
Published: July 2002

Gap-filling dynamics of several different species of additives for copper electrodeposition was investigated by monitoring the cross section of a partially filled copper profile on the scanning electron microscopy photo. The filling ration Δy/Δx between “bottom-up” with “sidewall shift” was found to be proportional to the filling power of additives. The adsorption-diffusion model combined with cathode polarization and cyclic voltammetric stripping measurements was employed to explain the attribution of additives in superfilling phenomena. The superfilling dynamics was achieved under behavior of additives providing selective inhibition gradient within the damascene feature. By means of those analyses, we have optimized the appropriate amount of additives and achieved the superfilling performance for 0.15 μm vias with aspect ratio 6 by an acid-copper electrolyte with polyethylene glycol, C1−, and 2-mercaptopyridine (2-MP). Due to the additive of 2-MP, chelate formed which enhanced adsorption ability on Cu0 surface, and the concentration gradient between side-wall shift and bottom-up in the damascene became high enough to attend superfilling electroplating.
Process and fabrication of a lead zirconate titanate thin film pressure sensor
Authors: Zakar E. , Dubey M. , Piekarski B. , Conrad J. , Piekarz R. , Widuta R.
Published: July 2002

Lead zirconate titanate (PZT) ferroelectric material is highly attractive for sensor and actuator device applications. Static pressure sensor structures were fabricated using sol-gel deposited PZT spin coated onto Pt/SiO2/Si substrates, with the platinum layer forming the bottom electrode. A subsequent platinum layer deposited onto the PZT formed the device top electrode. The resultant Pt/PZT/Pt/SiO2/Si stacks were patterned with photoresist and defined by ion beam milling and reactive ion etching in a HC2ClF4 plasma to form electrical capacitor structures. Capacitance measurements were performed on 200 μm×200 μm and 300 μm×300 μm dimension structures over the frequency range 0.12–100 kHz. Capacitance remained relatively unchanged over this frequency range, with a magnitude corresponding to its predicted value along with a low dissipation factor (0.02), thus verifying the high quality of the device structures. The device is intended to measure pressure in the range of 10 000–100 000 psi.
Texture studies of Si1−xGex thin films by x-ray diffraction and transmission electron microscopy
Authors: Qin W. , Ast D. G. , Kamins T. I.
Published: July 2002

X-ray diffraction (XRD), transmission electron microscopy (TEM), and transmission electron diffraction (TED) were used to measure the texture of undoped poly-Si1−xGex thin films with x=0, 0.018, 0.13, and 0.31. The films were grown by chemical vapor deposition onto oxidized Si wafers covered with a thin poly-Si seed layer, which was deposited using SiH4 to assist nucleation. SiH2Cl2 was used to deposit the poly-Si reference sample, and SiH2Cl2 mixed with GeH4 was used for Si1−xGex. To span a wide range of Ge content, the deposition temperature was lowered from 800 °C (x=0) to 600 °C (x=0.31) as the Ge fraction increased. All films, independent of Ge content (0⩽x⩽0.31), showed similar XRD spectra. The spectra exhibited a strong {110} fiber texture, with the intensity for differently oriented grains decreasing in the sequence {110}, {311}, and {111} for all films, even though grains in the seed layer appeared to be randomly oriented. Wedge-shaped specimens analyzed by TED showed that {110} texture was already present at the bottom (film/seed-layer interface) of all the films investigated and increased toward the top (film/air interface). Cross-section TEM images showed that all films exhibited a columnar structure and contained numerous V-shaped grains. Plan-view TEM showed the presence of numerous microtwins in all films. The results suggest that, under our experimental conditions, similar mechanisms dominate the development of texture in Si1−xGex and in poly-Si.
Calibrated variable leak for use in ion source operation
Authors: Langley Robert A. , Dastoor Paul C. , O’Connor D. John
Published: July 2002

An existing accelerator ion source has been modified to allow gas flow control from ground potential as opposed to control at high voltage as had been used. The mode of achieving this objective was to use a pressure reduction device at the gas entrance of the ion source so that the gas feed line could be maintained at a high pressure so that no arcing would occur. A pressure reduction device was developed which allows reproducible gas flows through and a pressure differential across the device. The development and production of the calibrated variable leak is discussed in detail. The components used are inexpensive and readily available, as are the tools necessary for construction and testing. A simple vacuum system was utilized for testing and calibrating the leak which had a dynamic range of more than 200 for a nominal pressure ratio across the leak of 50. A typical mass flow at a pressure ratio of 50 is 6×10−3 T L/s for nitrogen with a nominal conductance of 4×10−4 L/s. The vacuum system design program, VSD-II, was used extensively to determine the values necessary for mass flow, pressure, and conductance of the leak. This calibrated variable leak can be used in many applications other than in accelerators.
Gravity-related transport in reactive off-axis sputtering deposition?
Authors: Zhu Shen , Su C.-H. , Lehozeky S. L.
Published: July 2002

An experiment was performed to investigate the transport characterization of reactive off-axis sputtering deposition. Due to the collision and/or thermalization process between the sputtered species and background gases, three transport regions were observed when the growth pressures were varied from 5 to 150 mTorr. A gravity-related phenomenon was revealed in film growth at relatively high growth pressures by measuring film growth rate at two depositing orientations, which was either parallel or perpendicular to the gravity vector. In this study, possible design for the substrate holder orientation in the off-axis sputtering system was also suggested.
Line of sight techniques: Providing an inventory of all species arriving at and departing from a surface
Authors: Chan A. S. Y. , Skegg M. P. , Jones Robert G.
Published: July 2002

Line of sight (LOS) techniques comprise those methods in which species emanating from a surface (atoms, molecules, and radicals) undergo just a single pass through the ionization volume of a mass spectrometer before being pumped. This is achieved by enclosing the mass spectrometer within a cryoshield fitted with appropriate apertures, such that line of sight is established only between a patch on the sample surface (≈7 mm diameter) and the ionization volume. All LOS techniques are free from extraneous signals and have approximately equal detection probabilities for all species. Line of sight temperature programmed desorption, sticking probability (LOSSP), and product desorption (LOSPD) provide powerful and reliable ways of studying all aspects of surface kinetics, by allowing an inventory of all species arriving at and departing from a surface, for any combination of partial pressures, surface temperature, surface composition, and surface structure. Here we illustrate LOSSP and LOSPD using the reactions of 1-bromo-2-chloroethane, BrCH2CH2Cl,(BCE) and iodotrifluoromethane, CF3I, on Cu(111). For BCE we show that there is a 1:1 correspondence of product ethene to reactant BCE during dissociative adsorption at T>253 K, and that the dissociative adsorption is nonactivated with a transition state 11±2.5 kJ mol−1 below zero (0=molecule at infinity). For CF3I dissociative adsorption occurs at room temperature with a sticking probability of 0.96±0.02 to produce CF2⋅ which can either desorb as gaseous CF2⋅ radicals (observed) or undergo a coupling reaction and then desorb as gaseous C2F4 (also observed). No other gas phase products were observed.
Comparison of plasma chemistries and structure-property relationships of fluorocarbon films deposited from octafluorocyclobutane and pentafluoroethane monomers
Authors: Agraharam Sairam , Hess Dennis W. , Kohl Paul A. , Bidstrup Allen Sue Ann
Published: July 2002

Fluorocarbon films are deposited from mixtures of pentafluoroethane (PFE)/argon and octafluorocyclobutane/argon in a parallel plate reactor at pressures of 0.75 and 1 Torr and substrate temperatures between 120 and 240 °C. These monomers are compared in terms of plasma dissociation chemistries as well as chemical structure and properties (electrical, thermal, chemical, and optical) of the resulting films. Deposition rates with C4F8 are significantly higher than CF3CHF2. With both monomers, the deposition rate decreases with an increase in substrate temperature, indicative of an adsorption limited process. Films deposited from both monomers are analyzed using Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and capacitance measurements. XPS analyses indicate a higher flourine to carbon ratio for films deposited from C4F8. Likewise, these films have lower refractive indices (n∼1.38–1.39) and lower dielectric constants (k∼2.18–2.33) than PFE films (n=1.41, k=2.23–2.55). Films deposited from both monomers exhibit high dielectric losses (∼10−2–10−3) at deposition temperatures >200 °C. TGA analyses of films deposited from both monomers indicate comparable thermal stabilities up to a temperature of 300 °C. However, the decomposition rate is much higher for C4F8 films in the temperature range between 300 and 425 °C. Thermal stability of films deposited from both monomers is enhanced at higher deposition temperatures. However, the sensitivity of thermal stability to deposition temperature is lower for films deposited from C4F8. A tradeoff exists between the electrical properties and thermal stability of films deposited from both monomers.
Depth of origin of sputtered atoms for elemental Al and Mg targets in physical vapor deposition processes
Authors: Bordes J. M. , Bauer Ph.
Published: July 2002

The TRIM.SP Monte Carlo type program is used to calculate the escape depths for sputtered aluminum and magnesium target materials in physical vapor deposition processes involving argon plasma. Escape distributions are established for all sputtered atoms, as well as for sputtered atoms at several energies, in the case of normal impinging Ar ions. Distributions are also performed for several incidence angles up to 80°, in connection with recoils in collision cascades at a given energy. Mean escape depth calculations show that sputtered Mg atoms originate deeper underneath the surface compared to Al atoms, in accordance with their total stopping powers and sputtering yields. But, as a whole, the majority of sputtered Al and Mg atoms would come from the first two top layers.
Morphology and characteristics of C60 thin films grown in argon atmosphere by thermal evaporation
Authors: Zhang Haiyan , Wu Chunyan , Liang Lizheng , He Yanyang , Zhu Yanjuan , Chen Yiming , Ke Ning , Xu J. B. , Wong S. P. , Wei Aixiang , Peng Shaoqi
Published: July 2002

The surface morphology, structure, and optical absorption characteristics of C60 thin films grown in argon atmosphere by thermal evaporation have been studied. X-ray diffraction studies reveal a mixture phase of face-centered-cubic and hexagonal-close-packed phases for this film. Infrared analyses show no evidence of chemical change. The observations of atomic force microscopy of C60 thin films grown in argon atmosphere found that surface particles are larger and sharper than that grown in vacuum, thus C60 thin films grown in argon atmosphere may be advantageous to using C60 for electron field emission. Ultraviolet-visible optical absorption spectrum of this film in the range of wavelength from 200 to 600 nm is very different than that of the film obtained under vacuum conditions. The position and intensity of absorption peaks are obviously changed compared to vacuum C60 thin film. The band gap energy of this film also changes from 2.02 to 2.24 eV compared to the film prepared under vacuum.
Molecular beam epitaxial growth and characterization of strain-compensated Al0.3In0.7P/InP/Al0.3In0.7P metamorphic–pseudomorphic high electron mobility transistors on GaAs substrates
Authors: Hoke W. E. , Lemonias P. J. , Kennedy T. D. , Torabi A. , Tong E. K. , Chang K. L. , Hsieh K. C.
Published: July 2002

A novel metamorphic high electron mobility transistor (HEMT) structure was grown on GaAs substrates by solid-source molecular-beam epitaxy for potential microwave power applications. The HEMT device layers were strain compensated with pseudomorphic (tensile-strained) Al0.3In0.7P donor–barrier layers and a pseudomorphic (compressive-strained) InP channel layer. Atomic force microscopy measurements of the metamorphic structure yielded a root-mean-square surface roughness of 8 Å. Transmission electron micrographs of the device layers exhibited flat interfaces with the dislocation density estimated to be less than 1×106 cm−2. Room temperature photoluminescence measurements of metamorphic AlInP layers indicated large direct band gaps up to 2.10 eV. Due to the larger conduction band discontinuity at the Al0.3In0.7P/InP heterojunction than the AlGaAs/InGaAs heterojunction in GaAs pseudomorphic HEMTs, significantly higher channel sheet densities were obtained. For Al0.3In0.7P/InP HEMTs, channel sheet densities (cm−2) exceeding 3×1012 for single-pulse-doped, and greater than 4×1012 for double-pulse-doped, structures were readily obtained. Hall measurements on a double-pulse-doped Al0.3In0.7P/InP/Al0.3In0.7P HEMT gave mobilities (cm2/V s) of 4450 at 300 K and 18 500 at 77 K, which are consistent with a high quality InP channel layer. Secondary ion mass spectroscopy depth profiles of a double-pulse-doped structure displayed sharp doping pulses and interfaces indicating that metamorphic growth was not leading to enhanced diffusion or migration. Initial and nonoptimized devices with a gate length of 0.15 μm exhibited a maximum current density of 500 mA/mm and a transconductance of 520 mS/mm, which compare favorably to mature AlGaAs/InGaAs pseudomorphic HEMTs.