bluuebunny/crossref_metadata_2025 huggingface dataset:
Structure property relationships in deposits produced by plasma spray and detonation gun techniques
Authors: Tucker R. C.
Published: July 2002

The microstructures of materials produced by plasma spraying or detonation gun techniques consists of thin lenticular particles with a very fine grained (perhaps even amorphous) structure. They are rapidly quenched from the molten, or near molten state, and may have a high degree of residual stress. This review is concerned with the relationship between these unique microstructures and the properties of the material. The areas of bond strength, transient and residual stresses, density, corrosion characteristics, and wear resistance, as well as mechanical, thermal, and electrical properties are at least briefly surveyed. The methods of deposition, i.e., plasma torch operating conditions, heat transfer to the particles, etc., are not covered. It is evident that, although a sufficient amount of information is available for most engineeering applications of these materials, a great deal remains to be learned about the fundamental relationships between their structure and properties.
Shape engineering: A novel optical proximity correction technique for attenuated phase-shift mask
Authors: Pau S. , Bolan K. , Blakey M. , Nalamasu O.
Published: July 2002

Modifications of the shapes and relative orientations of contact windows in attenuated phase shifting mask are studied theoretically and experimentally to maximize process latitude and resolution and to minimize sidelobe printability. By utilizing a non-square contact window shape and maintaining the overall pattern transmission, we achieve considerable sidelobe suppression with no loss in process latitude and resolution.
Characterization of field stitching in electron-beam lithography using moiré metrology
Authors: Murphy T. E. , Mondol Mark K. , Smith Henry I.
Published: July 2002

We describe a method for characterizing field stitching in e-beam lithography systems. The method, which is based upon the moiré principle, enables one to measure interfield stitching errors to the nanometer level using only a conventional optical microscope. The technique is more sensitive than the commonly used vernier method, and it does not require the use of a coordinate-measuring tool. Our experiments show that this technique can determine the interfield stitching to within 2 nm.
Simulating the mechanical response of electron-beam projection lithography masks
Authors: Jachim A. F. , Chen C.-F. , Engelstad R. L. , Lovell E. G. , Mangat P. J. S. , Dauksher W. J.
Published: July 2002

This article describes the results of distortion simulations for Motorola’s 200 mm electron-beam projection lithography (EPL) mask due to the fabrication process, pattern transfer, and mounting. Finite element models have been created as predictive tools, which incorporate the orthotropic elastic material properties of single crystal silicon. Both membrane-flow and wafer-flow processes have been simulated, identifying the significant advantage of the former. Modeling results for parametric studies of the fabrication process and the effects of mounting under gravitational loading are presented. The predictive studies illustrate that the metal layer (Cr/TaSiN) stress most strongly influences the image placement error. It is also shown that common mounting techniques for e-beam writing and exposure are essential for minimizing pattern placement errors.
Application of the generalized curvilinear variable axis lens to electron projection
Authors: Stickel W. , Langner G. O.
Published: July 2002

The concept of the curvilinear variable axis lens (CVAL) has been introduced for the optics of projection reduction exposure with variable axis immersion lenses, an approach to electron projection lithography reported elsewhere. In the proof-of-concept system the special case of a planar CVAL following the fundamental imaging ray of the lens system was implemented and next generation lithography-commensurate performance was demonstrated. The present work addresses the question of whether general types of CVAL with different configurations of the optical elements are practical and acceptable in performance. Specifically, an analysis is presented of the performance trends of such optics in terms of blur and distortion depending on configuration, number and position of the optical elements in the system, as well as their relative drive requirements.
Sub-100 nm silicon on insulator complimentary metal–oxide semiconductor transistors by deep ultraviolet optical lithography
Authors: Fritze M. , Burns J. , Wyatt P. W. , Chen C. K. , Gouker P. , Chen C. L. , Keast C. , Astolfi D. , Yost D. , Preble D. , Curtis A. , Davis P. , Cann S. , Deneault S. , Liu H. Y.
Published: July 2002

We report results on the fabrication of deep sub-100 nm silicon-on-insulator (SOI) complimentary metal–oxide semiconductor transistors using phase-shift double-exposure deep ultraviolet optical lithography. Resist gate features down to 40 nm were resolved corresponding to λ/6 resolution or k1=0.1. Using an etch bias, we have fabricated polysilicon gate features down to 25 nm corresponding to λ/10 resolution or k1=0.06. Good process latitudes were obtained, and SOI transistor results down to 50 nm gate length are reported.
Saturation Density of Stable Clusters in Thin Solid Films: Random-Walk Corrections
Authors: Pocker D. J. , Hruska S. J.
Published: July 2002

Expressions for the saturation density of stable solid clusters, as formulated by Lewis and Campbell, are considered and modified. Consideration of the path behavior of randomly migrating monomer shows that the size of trapping areas is reduced by a factor of 10 in typical cases. Computational methods are illustrated to facilitate calculation of desorption and migration activation energies from saturation density data.
A Technique for Evaluating Titanium Alloys by Melting, Processing, and Testing Miniature Ingots
Authors: Morton A. G. S. , Pond R. B.
Published: July 2002

A technique of melting, processing, and testing small (80 g) rods of titanium alloys has been developed. The technique is designed for screening large numbers of alloy formulations to determine those with enough potential for further evaluation. The hearth plate of an arc button-melting furnace was modified to produce rod ingots which are forged to a shape suitable for testing. Strength and toughness measurements are used to compare a series of alloys relatively, and with respect to their bulk properties. It is recognized that a number of factors, such as cooling rates and amount of forging, prevent duplication of production material properties. Nevertheless, the apparent alloying and microstructural effects and the degree of correlation with plate properties are discussed.
High-Rate Physical Vapor Deposition of Hafnium Foil—A Feasibility Study
Authors: Bunshah R. F. , Webster R. T.
Published: July 2002

The high-rate physical-vapor-deposition process has been used to produce high-purity ductile hafnium foil. The ductility of the foils in the 0.001–0.002-in.-thickness range is excellent. The thinner foils (<0.001 in. thick) are considerably less ductile. There appears to be an inverse correlation between the ductility of the foil and the number of pinholes. Elimination of these should improve the ductility of the thinner foils.
Variable Bandgap Semiconducting Alloys
Authors: Dixon Jack R.
Published: July 2002

A considerable amount of basic and applied research has been directed toward the study of the lead chalcogenide semiconductors PbS, PbSe, and PbTe. Recently, it has been shown that when Sn is added to these compounds, the resulting semiconducting alloys are characterized by the variability of their valence-conduction bandgap Egap. In particular, it has been demonstrated that by changing the alloy composition or sample temperature, Egap can be made to vary over wide ranges including very small values. The widespread interest in these variable gap semiconductors stems largely from the fact that they represent fertile materials for (1) the development of new devices, and (2) the basic study of electrical, optical, and thermal phenomena under the unusual conditions of small and controllable bandgaps. Recent research in this area will be reviewed with particular emphasis on the role played by film technology.
Properties of Nickel Ferrite Films dc-Sputtered in Argon-Oxygen Mixtures
Authors: Westwood W. D. , Eastwood H. K. , Sadler A. G.
Published: July 2002

Films have been deposited on glass substrates by dc diode sputtering a polycrystalline nickel ferrite cathode in argon–oxygen mixtures containing between 0% and 67% oxygen. While the films deposited at zero oxygen content consist of randomly oriented nickel ferrite grains, the lattice constant increases from 8.35±0.02 to 8.415±0.025 Å with increasing oxygen content and the films become increasingly (100) oriented. The etch rate for the films decreases as the ordering increases. The deposition rate is approximately 5 Å/min but decreases with increasing oxygen content. Although the films could not be magnetically saturated at field strengths up to 14 kOe, values of the saturation magnetization obtained by extrapolation decreased with increasing oxygen content, but were much lower than for bulk nickel ferrite. The coercive force was also much higher than for bulk nickel ferrite.
Fabrication of rf-Sputtered Barium Titanate Thin Films
Authors: Pratt I. H. , Firestone S.
Published: July 2002

Barium titanate (BaTiO3) was deposited onto Pt foil, and onto thin-film Pt and Pt-Rh electrodes on sapphire, and counterelectroded to complete metal-dielectric-metal structures. Dielectrics (5000–60 000 Å) were deposited at substrate temperatures from 23 ° to 1000 °C, some fired in air at temperatures to 1400 °C after deposition, the films providing a wide range of dielectric constants (16–1900). Onset of BaTiO3 crystal growth was detected at 500 °C, a reduced BaTiO3 detected at 1000 °C, and constant Ba/Ti ratios measured over the deposition temperature range. Capacitance increase with temperature was essentially linear, with the fired dielectrics showing minimum slope. Tanδ varied from 0.005 for amorphous films to 0.065 for films with highest dielectric constants, with related dielectric strengths of 1.8×106 to ≈0.15×106 V/cm, respectively. Substrate, electrode, and process limitations for capacitor fabrication are defined.
Low-Temperature Resistance of Thin Films of Gold on Silicon
Authors: Otter F. A. , DeLange O. L. , Abbink H. C.
Published: July 2002

Thin films of Au on single-crystal Si in the nominal size range 10–30 Å have been prepared in ultra-high vacuum. The low-temperature electrical resistance of the films has been measured, and some of the films have been studied in the electron microscope. At helium temperatures, the resistance-temperature behavior is semiconductorlike for those films showing continuity. Activation energies are 0.73 and 0.78 for two films deposited on (111)Si and having C overlays. A film on (100)Si having a Si overlay yielded an activation energy of 0.37 K. Electron microscope studies indicate that one of the films (nominally 30 Å thick) consists of a fairly uniform film 10 Å thick with the rest of the Au in micron-sized blobs. The 10 Å film shows no Au structure, and we speculate on the basis of this and the resistive behavior that there is a surface stabilized compound of Au and Si. A compound is consistent with the segregation of Au to the Si surface reported by Bishop and Rivière.
A Simple Quadrupole Residual Gas Analyzer
Authors: Rettinghaus G. , Huber W. K.
Published: July 2002

Based on our experience with the quadrupole mass spectrometer, an instrument of reduced size, complexity, and with high economy was developed as a gauge for simple residual gas analysis in the high vacuum and down to the ultrahigh vacuum range (limit of detection: 5×10−11  for N2 with unit resolution up to mass 100). The small system can be mounted almost completely as a nude system. No secondary electron multiplier is used. The high vacuum version is bakeable up to temperatures tolerated by Viton gaskets. It is compatible with most of the existing flanges as well as with future types (smallest diameter of the port: 32-mm i.d.). The uhv version (bakeable to 400 °C) is normally mounted on a 2.75-in. (7-cm) o.d. Conflat flange. The importance of the various parameters influencing the operation conditions is discussed in detail considering the restricted range of application.
High-Vacuum Calibration of a Cryogenic Quartz Crystal—An Atmospheric Density Gauge
Authors: Youngblood Wallace W.
Published: July 2002

Details of a vacuum calibration of a cryogenically cooled, quartz crystal density gauge are related and the results presented. The gauge (or cryogenic densitometer) design is based on a liquid-helium-cooled quartz wafer (AT cut 39 ° 45 min) resonating in its thickness shear mode. Holding the temperature of the quartz crystal below about 15 K permits “cryopumping” of the condensable gases arriving at its surface. Since the frequency of such a crystal shifts monotonically with changes in its mass, the change in frequency can be related directly to the mass density of molecules condensing on the crystal’s surface. This mass density may be further related to ambient pressure outside of the gauge by a priori knowledge of the gauge geometry, sensitivity, and other parameters. The sensitivity of the gauge in its present geometry was found to be approximately 1.703×108 Hz/g for molecular nitrogen. The gauge is being prepared for use as a unique atmopheric density probe in the approximate altitude range of 140–180 km.
Ultrahigh Vacuum Hardware
Authors: Milleron Norman
Published: July 2002

My remarks are offered as personalized comments concerning the “nitty gritty” of uhv hardware. These opinions are drawn from 18 years of work-a-day experience with large and small uhv systems (no unannotated literature survey here). Emphasis is placed on valves, permanent and demountable joints, gaskets, flanges, and vessels rather than pumps, traps, baffles, bell jars, complete systems, and other uhv hardware. My remarks are offered under the assumption that it is more fruitful in the practical world (as well as in theory) to define uhv as a multiparameter environment, a crucial step being to identify and control those parameters of importance in each specific application. (Note: pressure in a gas and/or the sum of the partial gas pressures are seldom of much importance.) What can be tolerated can be as important as how much. Proceeding thus, the probability of molecules entering and leaving a system as a function of time, temperature, chemical and physical kind, history, techniques, materials, work processes, pumps and equipment used, geometry, etc. is a focusing point of view. Consequently, stress is placed on handling, cleaning, machining, welding, surface treatment, and fabricating (in addition to design) in order to provide guidelines about what to do and avoid.
Differentially Pumped Ion Nitriding Furnace
Authors: Denton Richard A.
Published: July 2002

Ion nitriding hardening of steel surfaces has required a very special high-voltage cathode insulator supporting the work. The water-cooled chamber is grounded and is the anode of the system. A glow discharge at about 1000 V and pressures in the 1–15 Torr range in an atmosphere of mixed nitrogen and hydrogen heats the work to 1000 °F while bombarding its surface with nitrogen ions forming the hardening nitrides. A system with the cathode at ground potential has been built by inserting an intermediate chamber between the work-holding structure and the enclosing chamber. It was found easy to maintain the required pressures within the intermediate, reactive chamber while maintaining a vacuum high enough to eliminate glow discharge between the chambers. A description of the construction and operation of the equipment is given. It is proposed that this type of equipment could also be used for various thin-film components such as tantalum nitride resistors. Other gases could also be employed.
Production Scale Electron-Beam Systems for Thin-Film Applications
Authors: Overacker Walter G.
Published: July 2002

This paper describes recent advances in the design and operation of automated systems which lock the work in and out of the evaporation area. The latter is maintained under vacuum at all times with the sources in a continuously ready state. Systems have been produced for up to five sequential or graded coatings and for alloys. Each deposition is monitored and each step must be completed to specification before the next step can be started. Very high production rates can be achieved, and users report the end product superior to that obtained from batch systems opened to air between loads. Operation of such systems over long periods has created some unique operating problems and solutions.
Field Ionization Data Using a Graphite Emitter
Authors: Bryant P. J. , Gutshall P. L. , Clow W. L.
Published: July 2002

The ionization yield for various gases has been examined utilizing the lateral surface of a single graphite whisker as the ionizer. The process of ion formation at or near the inert-type surface has been compared with data from a platinum wire ionizer. The dependence of ion yield upon applied voltage has been obtained and plotted for a range of values from 7.5 to 20 kV. A series of gases were examined which provided a range of values for the parameters of interest such as ionization potential. The gases studied included helium, ammonia, carbon monoxide, carbon dioxide, sulfur dioxide, methane, and ethylene.
Emission Decay of Oxide Cathode Induced by Electrode Contamination
Authors: Kai J. , Koitabashi M. , Watanabe K. , Morihiro Y.
Published: July 2002

The emission decays of the oxide-coated cathode due to the contamination of the positive electrode have been studied with barium fluoride as the contaminant. All the experimental processes—positive electrode (anode) cleaning by electron bombardment, vacuum deposition of a known amount of the contaminant onto the anode, and dc and pulsed emission measurement—were carried out in a vacuum system using movable molybdenum anodes. As soon as an anode voltage higher than about 10 V was applied, the emission decayed to a minimum value, and then increased slowly. The minimum emission seemed to occur when the incoming rate of poisoning material to the cathode became equal to its liberation rate from the cathode. The emission decay was detected even with 5×10−8 g/cm2 of barium fluoride. The emission recovered gradually when the anode was replaced by a clean one. The decay-recovery process proved repeatable at least 15 times and the activation energy of the recovery was estimated to be about 36–45 kcal/mole, when the amount of the contaminant was 2×10−6 g/cm2. The decay and recovery processes are discussed.
Residual Gases Present during the Outgassing and OAOR Cycling of Silver
Authors: Biegen J. R. , Czanderna A. W.
Published: July 2002

High-purity silver powder (99.97%) subjected to isothermal outgassing, oxygen adsorption, outgassing, and chemical reduction (OAOR cycling) at 320 °C has been shown to contain 750 ppm of unreported volatile impurities and to be reproducible to the chemisorption of oxygen and other gases. To determine some of the volatile contaminants present before cycling and the effect of cycling on their release by the sample, a residual gas analyzer was used to study the gases which were desorbed by heating a sample of silver powder in stages to 900 °C in vacuo. A second sample was subjected to five OAOR cycles at 320 °C and then outgassed in stages up to 900 °C. During the isothermal outgassing of the uncycled sample, the partial pressures of carbon monoxide, carbon dioxide, oxygen, water, argon, and sulfur dioxide increased by as much as ten times between 300 ° and 410 °C and again between 540 ° and 565 °C. The increase in the residual gases results from a combination of bulk diffusion, surface reaction and desorption, and possibly the release of gases trapped in voids in the powder. Similar increases were seen for the cycled sample, except that sharper peaks were found in the temperature ranges of 505 °–535 °C and 720 °–730 °C. A third sample was OA cycled at 500 °C and outgassed in the same manner. Similar increases of the same impurities were found between 740 °–760 °C. Since silver powder sinters on outgassing above 200 °C, cleaning by chemical reduction cannot be carried out without strongly sintering the sample.
Oxidation of a Ternary Uranium Alloy
Authors: Larson D. T.
Published: July 2002

The effect of alloying uranium with 7.5-wt% Nb and 2.5-wt% Zr (“Mulberry” alloy) on the initial oxidation kinetics (surface oxide thicknesses up to 2000 Å) in air containing water vapor was investigated using an ellipsometer high vacuum system. The uranium alloy samples were oxidized in dry air (<5 ppm H2O) and air containing water vapor (15 000 ppm H2O) at a pressure of 650 Torr in a temperature range of 22 °–200 °C. The results differed from the oxidation of uranium in that the oxidation of this uranium alloy was not enhanced by water vapor under the conditions studied. The oxidation of unalloyed uranium in air is accelerated by water vapor. The oxidation followed a parabolic-rate law, indicating a diffusion-controlled mechanism. An Arrhenius plot of the parabolic reaction rates as a function of the reciprocal temperature revealed a difference in the activation energy of the low-temperature (22 °–100 °C) and high-temperature (100 °–200 °C) oxidation.
Influence of Impurities on the Surface Structures and Fault Generation in Homoepitaxial Si(111) Films
Authors: Thomas R. N. , Francombe M. H.
Published: July 2002

In situ LEED studies of the homoepitaxial growth of Si(111) films by uhv sublimation, indicate a strong correlation between the type of surface structure generated and the metallic impurity content of the silicon substrates as estimated from minority carrier lifetimes. The development of the familiar Si(4111)−7×7 structure is favored by the presence of lifetime-killing impurities in the substrate. Experiments where Fe is introduced on high lifetime substrates prior to annealing and film growth, suggest that this impurity species plays a role in the generation of the 7×7 surface structure. Electron microscopy reveals that homoepitaxial Si(111) layers are generally faulted, the number density of which increases progressively as the growth temperature is lowered. Films deposited on high-lifetime silicon contain substantially fewer stacking faults than those grown on low-lifetime substrates. These results suggest that the faults originate at microprecipitates at the substrate surface consisting of fast-diffusing, low-solubility impurity species.
Vapor-Phase Growth of Several III–V Compound Semiconductors
Authors: Tietjen J. J. , Ban V. S. , Enstrom R. E. , Richman D.
Published: July 2002

A review is presented of a vapor-phase growth method that has been developed for the synthesis of a broad spectrum of III–V compounds. The predominant feature of this technique is the use of gases as the source chemicals, thereby providing improved control of the chemical composition, homogeneity, crystalline perfection, and impurity concentrations and distributions of the epitaxial layers. As a result, a number of notable advances have been made with respect to the material properties and device utilization of several III–V compounds. The chemistry of the deposition processes was studied by means of a mass spectrometer coupled to the vapor-phase growth system. Results of these studies are presented and discussed.
Photoelectric Studies of Heteroepitaxial Semiconductor Films
Authors: Viswanathan C. R. , Loo R. , Ogura S.
Published: July 2002

Thin film heteroepitaxial silicon and GaAs grown on sapphire (Al2O3) were studied in an MIS configuration using a photoelectric technique. The Al2O3 substrate layer serves as the insulator and an aluminum film deposited on the other side of the substrate serves as the metal electrode. The results demonstrate that it is possible to transport photoexcited electrons across Al2O3 layers of several mils thickness. The photoelectric threshold energy value for the Al–Al2O3 is measured to be 3.85±0.05 eV while for the Si–Al2O3 and GaAs–Al2O3 interfaces, the values of the threshold energy are 4.5 and 4.4 eV, respectively. The electron affinity of the sapphire is found to be 0.42±0.07 eV. The amount of band bending in the semiconductor is obtained from the experimental results. It is also shown that the escape length of photoelectrons in heteroepitaxial semiconductor films is at least several microns in contrast with the low values (of the order of a few angstroms) quoted in the literature for bulk materials.
Gas Flow in Vacuum Systems
Authors: Dayton B. B.
Published: July 2002

Approximate equations have been derived for the molecular flow conductance of tubes with sharp bends or elbows, the conductance of two or more tubes in series with different cross sections or with diaphragms which involve junctions across which the gas molecules are scattered back and forth in complicated beaming patterns.
Parallel between Surface States at the Si–SiO2 Interface and the B2 Center in Irradiated SiO2
Authors: Hickmott T. W.
Published: July 2002

The effect of annealing in nitrogen and hydrogen atmospheres on surface-state densities Nss at the Si–SiO2 interface has been measured using the linear voltage-ramp method which gives Nss vs silicon surface potential. A mercury probe was used in order to eliminate the effect of aluminum on surface-state reduction. The dependence of annealing of surface states on atmosphere and temperature closely parallels that of the B2 center in sputtered SiO2, an absorption center with maximum absorption at 5.1 eV which is observed in irradiated SiO2. In N2, temperatures between 700°C and 800°C are required to anneal completely the B2 center; Nss reaches its lowest values after annealing in N2 at 700°C. In H2, the B2 center anneals completely and Nss is reduced to its lowest values after heating at 400°C. Annealing at 600°C or 700°C in H2 increases Nss and introduces a surface-state level ∼0.1 V above the midgap energy Ei.
rf Sputtering from Two-Phase Bi–Sn Cathodes
Authors: Shoemaker R. T. , Liedl G. L.
Published: July 2002

Sintered cathodes with Bi–Sn ratios over the entire composition range and using particle sizes from 50 to 150 μ were rf sputtered in an argon atmosphere. The composition and deposition rates of the sputter-deposited films were investigated and related to composition and particle size of the cathodes, total cathodes sputtering time, and gas pressure. In the initial stages of sputtering from newly ground cathodes (less than 60 min) deposition rates increased with time and Bi concentration, and the amount of Bi deposited decreased with decreasing particle size in the cathode. A correlation between film composition and cathode composition was obtained using measured resputtering data and estimating the impinging flux at the substrate.
Electron Beam Exposure of Polymeric Resists
Authors: Sobanski J. , Chabicovsky R. , Schuler A.
Published: July 2002

Two types of polymeric resists were exposed to pulsed electron beams under the following conditions: accelerating voltage 26–34 kV, beam current 10−4A, pulse length 4 μsec-16 msec. The exposure latitudes of thin layers of polystyrene and poly(methyl methacrylate) were studied. These polymers are well qualified as, respectively, negative and positive acting resists. However, poly(methyl methacrylate) with an average molecular weight below 20 000 is not resistant to etchants because of the pin-hole formation during developing.
Optical Transmittance of Partially Oxidized Copper Films
Authors: Czanderna A. W. , Boyko F. L.
Published: July 2002

The optical transmittance, measured from 400 to 800 μm during the complete oxidation of copper films to CuO0.67 at temperatures below 200 °C, has been used to test a model of oxidation by parallel layers. The transmittance at each stage of oxidation was calculated from the thickness of the oxide and metal layers, the optical constants, and the assumption that two homogeneous parallel absorbing layers exist at all stages. By comparing the calculated and experimental values of transmittance, the validity of the “parallel layer” model was established for nearly all stages of oxidation. Deviations in the initial stages are attributed to nucleation. Films oxidized at temperatures exceeding 147°C showed evidence of agglomeration of the metal in the terminal stages of oxidation. The films, deposited at 25°C on Pyrex substrates, are strained. Thus, when they were heated to the oxidizing temperatures of 125°–200°C, they were oxidized and also annealed. The optical constants for strained copper films are compared with those for annealed films at 400, 450, 500, 550, and 700 μm. Calculated changes in the transmittance at 550 μm are given for the parallel-layer oxidation of annealed copper films initially 200 to 700 Å thick.
Non-Steady-State Measurements on Variable-Threshold MNOS Transistors
Authors: Simmons J. G.
Published: July 2002

The variable-threshold MNOS transistor has powerful potential as an electronic memory element. It is generally acknowledged that charge storage in trapping levels at or near to the oxide–nitride interface are responsible for the memory effects. However, little or nothing is known about the parameters of the trapping levels, yet such knowledge is essential if device characteristics are to be optimized. The present study involves cooling the device to liquid nitrogen temperature while it is in the steady state, and then at the low temperature inducing a nonsteady state condition in the device. Subsequently, as the temperature of the sample is raised, at certain temperatures pronounced thermally stimulated peaks are observed in the relaxation current flowing in the system which may be related to the current flowing in the system which may be related to the trapping level parameters. Pronounced structure is also observed in the capacitance–temperature characteristics of the samples which may also be related to the trapping parameters.
Application of High-Resolution Shadow Casting to the Study of Nucleation and Growth of Gold on Sodium Chloride
Authors: Hayek K. , Schwabe U.
Published: July 2002

The method of tantalum–tungsten shadowing has been applied to investigate the initial stages of nucleation and growth of evaporated gold films on sodium chloride cleavage planes. Gold has been evaporated at a fixed evaporation rate at substrate temperatures ranging from 80 to 625 K and the surface plus evaporated layer were shadowed immediately with Ta/W. This treatment helps to prevent artifacts but also enables to distinguish easily between ordered and disordered parts of the NaCl substrate. It was found that the observed density of particles at “saturation” (Ns) is proportional to (exp a/T), where the constant a has two different values for the temperature ranges below and above about 298 K. Several possible interpretations of the occurrence of two activation energies are discussed.
The Detection of Current Filaments in Thin Amorphous Films
Authors: Schwartz R. J. , Luginbuhl H. W.
Published: July 2002

Switching and memory effects can be observed in many metal–insulator–metal structures. These phenomena are generally explained in terms of filamentary conduction through the insulator. The nonhomogeneous conduction causes a nonuniform potential in the top metal electrode. These small potential differences are detected with the aid of a scanning electron microscope. A special ac detection scheme is employed to improve the normal voltage contrast obtained in secondary electron micrographs. A fixed frequency ac bias is applied to the device and the secondary electron detector is narrowly tuned to this same frequency. This technique allows the suppression of normal topographical and compositional contrast and significantly improves the signal-to-noise ratio for voltage contrast. The presence of current filaments in Nb–Nb2O5–NiCr devices is experimentally verified.
Current Transport Mechanisms in Semi-Insulators Having an Injecting Contact
Authors: Barbe D. F. , McRae H. F.
Published: July 2002

The effect of Poole–Frenkel barrier lowering on trap-controlled space-charge-limited current in high-resistivity semiconductors and semi-insulators is considered. Both one- and three-dimensional models of trapping centers are treated. Analytical solutions are obtained in both cases. Close compensation is required for the Poole–Frenkel enhanced space-charge-limited current to be observed, and the current density derived from the three-dimensional trap model with electron injection from one of the contacts has exactly the same voltage and thickness dependence as the current density derived from the one-dimensional trap model without injection.
Interaction of Hydrogen Beams with Metal Surfaces
Authors: Chappell R. , Hayward D. O.
Published: July 2002

The angular distributions of hydrogen scattered from the surfaces of polycrystalline platinum and molybdenum, and from the (100), (111), and (110) faces of molybdenum single crystals have been measured. With platinum both a sharp specular peak and a subspecular peak have been observed, and these diminish in intensity as the surface becomes covered with hydrogen. The second peak is thought to result from diffraction. On a clean polycrystalline molybdenum surface, 68% of the incident beam is chemisorbed, 24% is diffusely reflected, and 8% is specularly reflected. It is found that the diffuse and specular components come from different crystal faces, the (100) and (111) faces giving predominantly diffuse scattering and the (110) face specular reflection.
High Rate Ion Production for Vacuum Deposition
Authors: Morley John R. , Smith Hugh R.
Published: July 2002

A high current, low voltage magnetically confined and bent hot hollow cathode discharge was used to simultaneously evaporate and to ionize materials under vacuum. At power levels of about 15 kW, (60V, 250A) evaporation rates of 4 g/min were observed for copper and quartz from a 3 in. diam water-cooled crucible. Two 6×6 in. substrates were mounted symmetrically 20 in. above the source one being at crucible (ground) potential, the other having a negative bias voltage (0–200 V) in order to collect ions. At a given evaporation rate, the biased substrate collected about twice as much copper and about five times the amount of quartz as that deposited upon the grounded substrate.
Electron Beam Float Zone Melting and Vacuum Degassing of Niobium Single Crystals
Authors: Reed R. E.
Published: July 2002

Niobium metal powder produced by electrodeposition from molten salts was electron beam float zone melted (EBFZM) for purification and growth of single crystals. It was necessary to EBFZM with a high oxygen partial pressure to reduce the carbon level. A high resistance ratio (R300 K/R4.2 K(15 kG)=6500) and low flow stress (τly=460 gm/mm2) was obtained after a high temperature anneal (2350 °C) in high vacuum (2×10−10 Torr). Extensive material characterization results are reported for the niobium at various stages in the purification process. The impurity content determined by chemical analyses did not correlate with the resistance ratios; however, the flow stress exhibited an excellent correlation with resistance ratio. These results imply that interstitial impurity in solid solution is the impurity distribution most affecting disslocation motion.
The Role of Surface Plasmons in Van Der Waals Attraction between Solids
Authors: Gerlach E.
Published: July 2002

As has been shown by Casimir, Van der Waals attraction between solids, separated by a gap, can be obtained from the ground state energy of all electromagnetic modes of the system. In the present paper it is shown that, in a slightly generalized sense, the retarded Van der Waals attraction corresponds to the ground state energy of the interacting surface plasmons on either side of the gap. This concept establishes an interesting connection between the large field of surface plasmon physics and numerous technical applications in the field of adhesion between solids.
Semiconductor Inversion Layers and Phonons in Half-Space
Authors: Kawaji Shinji , Ezawa Hiroshi , Nakamura Koichi
Published: July 2002

Electron-surfon interaction is used to calculate the mobility μ of electrons in the lowest subband in N-channel Si MOS-FET on the (111), (110) and (100) surfaces and at around room temperature. The surfons are the quanta of elastic waves in isotropic elastic continuum (which is to represent Si) occupying a half-space and having a stress-free plane boundary. In the approximations of high temperature surfon distribution and of elastic scattering, the result is (i) that the dependence of μ upon temperature and surface electron concentration can be fairly well reproduced but (ii) that the magnitude of μ has turned out to be about 10 times as high as the experimental values so far as bulk values are used for the deformation potential constants and for the effective masses of electrons. The correction due to the presence of SiO2 layer on Si is estimated to be small. It can be argued that correction due to intervalley scattering and electron population in the upper subbands are in the direction of improving the fit to the experiments. Still, the magnitude of μ remains unexplained unless the values of the deformation potential constants and effective masses of electrons differ in the surface region from the corresponding bulk values.
Low-voltage triode sputtering with a confined plasma: Part I—geometric aspects of deposition
Authors: Tisone T. C. , Bindell J. B.
Published: July 2002

Low-voltage triode sputtering is a film deposition process capable of high deposition rates (100–600 Å/min) using voltages less than 500 V and Ar pressures of about 1 μ. This paper considers the geometric aspects of low-voltage triode deposition which include: (1) the thickness uniformity over the substrate table; (2) step coverage; and (3) the geometric conditions that give the best thickness uniformity, step coverage, and maximum utilization of target area.
Thin Film Characterization by Nuclear Microanalysis
Authors: Ziegler James F.
Published: July 2002

Nuclear microanalysis is a nondestructive method for quantitatively profiling the constituents of thin films. It needs no calibration samples. It excels in determining atomic concentrations with depth, in finding reactions and diffusions across interfaces, and in detecting contamination. A summary will be given of recent work in the fields of dielectric films, metal alloy films, and profiling impurities in semiconductors.
Advanced Thin-Film Metallurgy for Beam-Leaded Integrated Circuits
Authors: Culver H. E. , Schilling H. , Thun R. E.
Published: July 2002

Interconnection metallizations of integrated circuits must exhibit good ohmic contact, chemical inertness, low atomic mobility, good adherence, high conductivity, and compatibility with metal-dielectric multilayering. This paper describes a multimetal interconnection system which provides both multilayer interconnections and beam leads. The film stack includes combinations of the following layers, depending on the specific functional surface area: platinum silicide, silicon dioxide, molybdenum, silicon nitride, chromium, titanium, platinum, gold, and glass. Chemical surface reaction, vapor deposition, cathode sputtering, and electroplating have been employed as deposition methods. Fabrication processes as well as test results obtained on complex integrated circuits are discussed in detail.
Partial Pressure Analysis Using A Two-Chamber Gauge Together with an Ion–Electron Converter
Authors: Ertl K. , Taglauer E.
Published: July 2002

A two-chamber device has been developed together with a very sensitive ion detecting system. The hot filament is placed in a separately pumped vacuum chamber, thus eliminating interaction effects of the filament with the residual gas. Electrons from the filament pass through a very small conductance orifice into the ionization chamber. The ions are detected with a tube-shaped ion–electron converter followed by a surface barrier detector. Single ion pulses can be counted and from the pulse height distributions the counting efficiency can be calculated for different ionic species. With counting losses of 3% or less for all ions, a background current of 4×10−21 A was measured. This leads to a minimum detectable partial pressure of about 10−15 Torr which can be extrapolated to an ultimate sensitivity of 10−17 Torr. The mass resolution of the magnetic analyzer is 190 (FWHM definition).
Pneumatic Logic Controls for Automatic Vacuum Systems
Authors: Hugenberger Charles E. , Petrich Donald E.
Published: July 2002

High-pressure modularly mounted diaphragm air logic elements are extremely useful in vacuum systems controls, because of their versatility, easy assembly, and freedom from effects of electrical noise. Systems designers without previous logic programming experience will find these systems relatively easy to design. The elements operate on clean house air from 25 to 150 psi and therefore require no amplification. Circuit designs and assembly procedures are discussed in detail, including optimized designs successfully used at LLL.
Chromium Deposition in a Rotary Drum Evaporator
Authors: Frieser R. G. , Brooks G. A.
Published: July 2002

A rotary drum evaporator has proved itself capable of depositing thin chromium films that are comparable if not superior to films deposited by other techniques. The thickness of the films is uniform and pinholes have been reduced to less than five per square inch. The model described is capable of handling 12 glass substrates of different sizes, but the design can easily be scaled up to accommodate even more.
Electrostatic Getter-Ion Pump Performance
Authors: Bills Daniel G.
Published: July 2002

Important characteristics of electrostatic getter-ion pumps are examined from the standpoint of the typical user. Results are presented from an experimental comparison of a sputter ion pump with an electrostatic getter-ion pump, both of which are commericially available and of about the same installed cost. Care was taken to insure identical conditions of use and operation during the testing on both baked and unbaked systems. A quadrupole RGA was used to insure that system conditions and gas composition were known. Data are presented for how well the pumps maintain their rated speeds, the ultimate pressures achieved, the ability to handle pressure bursts of N2, CO, H2, H2+N2, H2O, air, Ar, He, CH4, C3H8, memory, and regurgitation effects, and the ability to pump and rapidly cycle a very dirty unbaked glass bell jar evaporator.
Optical Conduction Resonance in Discontinuous Metal Films
Authors: Marton J. P.
Published: July 2002

Optical resonance absorption in discontinuous metal films is studied in the dipole approximation. In the free electron regime the phenomenon is closely related to plasma oscillations and can be treated analytically. When damping is present, approximations may be employed and the quantities of interest can still be expressed in closed form. In the interband transition region the free electron effects are further damped and the resonance frequency may be shifted. In this case no analytical treatment is practical. Real situations may be simulated, however, by adding a lightly damped oscillator term to the free electron dielectric function of the metal. A suitable choice of parameters can describe a real metal.
Laser Generated Thermoelastic Shock Waves in Liquid
Authors: Bushanam Gangadaran Siva , Barnes Frank S.
Published: July 2002

The interactions of lasers with matter are manyfold. Among the important interactions is the generation of pressure waves by laser heating in an optically absorbing dye. The conversion of energy from transient laser heating to an acoustic wave is considered in detail in this paper. As a laser pulse enters an absorbing dye, energy is absorbed and converted into heat. Part of it will appear as elastic energy in the form of a pressure wave, due to very small expansion in the dye during the laser pulse.
Recent Advances in Electron Beam Recording
Authors: Grosso Patrick F. , Tarnowski Andrew A.
Published: July 2002

This article describes recent advances in electron-beam recorders (EBR) which utilize the inherent flexibility of electron beams and computer control for a variety of applications such as remote sensor imagery, computer micrographics, microelectronics, and other high resolution digital and analog imagery. These advanced electron beam recorders can be used on-line with computers or remote sensors, or off-line with analog or digital magnetic tape inputs, in a variety of scanning modes using computer control.
Compression and Stability Studies of High ν/γ Beams
Authors: Stallings Charles , Schneider Richard , Benford James
Published: July 2002

Intense electron beams are of increasing interest in controlled fusion research. Such beams exhibit several phenomena which suggest strong coupling between the beam and the background plasma via beam-generated electromagnetic fields. Observations of beam compressibility and distortion in inhomogeneous fields are reported.
Transformer Type Accelerator—Compact Sources of Energetic Electrons
Authors: Simcox G. K. , Schubert C. J.
Published: July 2002

A family of electron accelerators is described which derives its relatively small dimensions from the dielectric strength advantages of a pulsed voltage mode and from advanced concepts of electron beam transport.
Molecular Acceleration by Alternate Gradient Focusing
Authors: Kakati D. , Choudhury A.
Published: July 2002

Some recent developments show that a neutral-particle accelerator (e.g., a molecular accelerator) can be an important tool not only to the chemical investigator but may also have potential use in an entirely new field namely solid-state device fabrication. Experimental evidence of alternate gradient focusing of neutral particles has already been reported by one of the authors elsewhere. This paper now presents a theoretical analysis and considers the possibilities of extending the work for construction of a neutral-particle accelerator. An ammonia molecular-beam is considered as an example. A particular advantage in this case is that the transported molecular beam can be analyzed in a conventional superheterodyne set up.
Ion scattering for analysis of surfaces and surface layers
Authors: Buck T. M. , Poate J. M.
Published: July 2002

This paper is a review of the principles, techniques, and some recent applications of ion scattering for surface and surface layer analysis. Three energy ranges, loosely defined as high (1–2 MeV), medium (100–400 keV), and low (0.5–10 keV) are discussed separately. We have not attempted a comprehensive review of such a large and rapidly growing field. Examples are taken mainly from experiments with which the authors are familiar. A summary table at the end shows the diversity of problems to which ion scattering has been applied.
Structure and properties of sputtered titanium carbide and titanium nitride coatings
Authors: Mah G. , Nordin C. W. , Fuller J. F.
Published: July 2002

A sputtering process has been developed for coating tungsten carbide cutting tools with titanium carbide and titanium nitride. For the titanium carbide coating, the x-ray diffraction results indicate that the coating has the stoichiometric composition as the target and has a (111) preferred orientation, Photomicrographs show the coatings to be of fine grain structure. The titanium carbide coating has hardness values of 2400 kg/ mm2 which are in agreement with the values of bulk titanium carbide. Effects of sputtering parameters on the coatings will be discussed also. Evaluations of coated tools versus uncoated tools show the coating increases the effective life of the tool, reduces tool force, and improves the surface finish.
Plasma hardening of high-chromium-alloy steel containing distributed titanium carbide
Authors: Gifford Fay E. , Cooley Keith W.
Published: July 2002

Plasma nitriding of steel-bonded carbides was investigated to determine if this process hardens the material. It is found that the nitriding and hardening occur only in the tool steel matrix by the formation of the compounds Fe3N-Fe2N, γ′-Fe4N, and Fe3N, and it is hardened to 1500 Knoop. A case depth of 0.15 mm (0.006 in.) is developed in 6 h at a temperature of 600 °C. Conventional heat treatment through hardens the material to 900 Knoop, compared to 700 Knoop as received.