Showing papers on "Evaporation (deposition) published in 1968"

Metal-silicon Schottky barriers

Abstract: Measurements have been made of the height of Schottky barriers obtained by evaporating metal films on to n-type silicon. In the case of surfaces prepared by chemical methods, the height of the barrier initially depends on the particular method of surface preparation, and subsequently shows a slow change with time, reaching a steady value over a period of days or even weeks. This final value is independent of the method of surface preparation, but depends on the choice of metal. For junctions made by evaporation on to silicon cleaved in an ultra-high vacuum, the barrier height shows no ageing and is substantially independent of the metal. These observations can be explained in terms of the existence of a thin oxide layer on the chemically prepared surfaces, together with the assumption that the density of surface states is about two orders of magnitude lower on the chemically prepared surfaces than on the cleaved surfaces.

On the ionization state of field evaporated atoms as measured in the fim‐atom probe

Abstract: Experiments to test the performance of an FIM‐atom probe have yielded data on the charge state of field‐evaporated atoms from clean tungsten and iridium surfaces. These data are presented and discussed in the light of current ideas about the process of field evaporation.

The epitaxy of copper on sapphire

Abstract: Epitaxial twinned single‐crystal films of copper have been grown on sapphire substrates by high vacuum evaporation in the temperature range 240–‐375°C. The presence of a twin relationship in copper deposited on the basal plane of sapphire was demonstrated and evaluated by x‐ray diffraction techniques. The epitaxy has been shown to be (111)Cu ∥ (0001)α−Al2O3; [211)Cu ∥ [2110]α−Al2O3. The films have been found to exhibit the bulk metal resistivity.

Pseudomorphic deposits of chromium on nickel

Abstract: Chromium films were prepared by evaporation of the metal in ultra-high vacuum onto the (001) surfaces of nickel. A shutter was moved between source and substrate during film growth so that films in which there were thickness gradients were obtained. The very thin (roughly 10 A) parts of the chromium deposits were face-centred cubic, and dislocations to accommodate part of the misfit between the lattices of nickel and f.c.c. chromium were present. Thicker deposits contained small nuclei of chromium in the stable b.c.c. structure.

The Growth of Oxide on Field-Ion Specimens of Iridium

Abstract: The ability of the field-ion microscope to obtain images, with atomic resolution, of a compound—iridium oxide—is proved and applied to a study of the oxidation of previously examined field-ion specimens Field evaporation of the oxide layers allows the observation of the metal-oxide interface and also the three-dimensional structure of the oxide layer From considerations of image contrast it is deduced that only the iridium ions in the oxide are imaged, but the oxygen ions do contribute to the image by modifying the nature of image points obtained from neighbouring iridium ions The oxide films examined were always polycrystalline and the nature of grain boundaries in the oxide and the extent of overgrowth deduced The original stages of oxidation were studied and it is concluded that nucleation occurs at particular crystallographic facets of the original tip (probably {102}) The texture of the oxide layer is seen to depend on the rate of increase of temperature

Effects of Ultraviolet Irradiation on the Properties of Evaporated Silicon Oxide Films

Abstract: The optical and dielectric properties of silicon oxide films formed by reactive evaporation of silicon monoxide are investigated. The films are prepared at a deposition rate of 4 A/sec in 1×10−4 Torr oxygen. The optical absorption of the films is found to increase with increasing substrate and source temperatures; these variations are consistent with previously reported chemisorbed oxygen and gas‐phase oxidation film‐growth mechanisms. Post‐deposition exposure to uv radiation affects both the optical and dielectric properties of these films. Optical absorption in the 200 to 400‐mμ wavelength region is essentially eliminated by 1 h irradiation for films deposited at 145°C or less; a residual absorption is evident for films prepared at a higher substrate temperature. The magnitude of the dielectric loss and relative dielectric constant, the variation of the dielectric loss and dielectric constant with frequency, and instabilities of the dielectric properties are decreased by the uv treatment. For example, a...

Production and properties of vacuum evaporated films of thorium fluoride.

Abstract: Experiments for the production of vacuum evaporated films of thorium oxyfluoride showed that these films cannot be produced by direct evaporation of thorium oxyfluoride, because this material decomposes at approximately 1000°C into ThF4 and ThO2. ThF4 evaporates at approximately 900°C and yields very stable films. The production of ThF4 films is described and the dispersion of the refractive index, the dielectric constant, and the useful range of high transparency are reported. Precautions for the handling of ThF4, because of its radioactivity, are given.

Inverted solid state diode

Abstract: THIS INVENTION RELATES TO A METHOD OF PRODUCING AN INVERTED THIN FILM SOLID STATE DEVICE, I.E., A SOLID STATE DEVICE IN WHICH A SEMICONDUCTIVE FILM IS DEPOSITED ON A HIGH WORK FUNCTIONAL METAL. THE INVERTED SOLID STATE DEVICE IS PRODUCED BY APPLYING A FILM OF HIGH WORK FUNCTION METAL TO A SURFACE AND THEN COOLING THE METAL BELOW ROOM TEMPERATURE WHILE A THIN FILM OF SULFUR IS DEPOSITED ON THE SURFACE OF THE METAL. A THIN LAYER OF CADMIUM SULFIDE IS DEPOSITED ON THE SULFUR TO PREVENT EVAPORATION, THE TEMPERATURE IS RAISED, AND THE DEPOSITION OF THE CADMIUM SULFIDE IS COMPLETED. DEPOSITION OF A THIN FILM OF LOW WORK FUNCTION METAL ON THE CADMIUM SULFIDE COMPLETES THE INVERTED SOLID STATE DEVICE.

Improved CdTe Solar Cell and Array Environmental Effects Investigation.

Abstract: : The output voltage of Cu2TE:CdTe heterojunction cells might be improved by using instead a pn homojunction, a metal:semiconductor barrier, or some other type of heterojunction. During the present quarter phosphorus diffusion has been used to form shallow pn homojunctions. Some photoresponse was noted, but severe current limiting was experienced due to high p-region sheet resistivity. Also re-examined was gold:CdTe barriers, formed by both evaporation and electroless deposition. One evaporated gold cell yielded unusually high open-circuit voltage (680 mv), but current (and efficiency) were relatively low. Work on short-circuit current improvement chiefly involved improving the area utilization factor from about 89% to 95%, using better evaporation masks and hold-down techniques. An attempt was made to gain extrinsic absorption of light by growing CdSe(x)Te(1-x) mixed crystal films, but no increase in current was noted. Two methods for calculating short-circuit currents and efficiencies from spectral response data are given. A non-linear relationship between output current and illumination intensity in thin film cells was noted and a method for taking this into account in efficiency calculations is given.

Growth and structure of single-crystal films.

Abstract: : This research project was concerned with basic research on the growth and structure of single-crystal films of metals obtained by evaporation in ultra-high vaccum onto two types of substrates: mica and metal single-crystal films. The films were prepared in an ion pumped bakeable ultra-high vacuum plant. It was necessary to design and build at our laboratory a series of bakeable devices for this work. (Author)

Thin film structural reinforcements for high performance composites.

Abstract: : The work is a continuation of the development of high modulus, high strength, low density composites, which have mechanical properties which are isotropic in the plane of the composite. Composites were made of multiple sheets of vacuum deposited boron or boron carbide applied to substrates such as aluminum foil or 0.5 mil polyimide (Kapton). Methods for increasing the degree of adhesion of boron and boron carbide to the substrate materials were developed. Experimental work indicates that the evaporation and deposition of boron and boron carbide was considerably less difficult than the evaporation and deposition of silicon carbide. Increased volume fractions of reinforcement in composites were obtained by use of temporary substrates. Samples of boron carbide, boron and silicon carbide on polyimide and boron carbide and boron on aluminum were supplied to AFML. (Author)

Improvements in or relating to the deposition of epitaxial layers

Abstract: In a process for depositing a semi-conductor material e.g. Si or Ge, on a Si substrate either by vacuum evaporation or chemical deposition, an oxidizing agent e.g. oxygen or water vapour is present at such a partial pressure that silicon monoxide and carbon monoxide are formed with little or no silicon carbide. In the evaporation process the substrate is at a temperature of 900 to 1350 DEG C. and the vacuum is 10-5 to 10-8 Torr. In the chemical deposition process the oxidizing agent is introduced during a preliminary stoving of the substrate in hydrogen at 1200 to 1250 DEG C.ALSO:In a process for chemically depositing Si on a Si substrate, an oxidizing agent e.g. oxygen or water vapour is introduced during a preliminary stoving of the substrate in hydrogen at 1200 DEG to 1250 DEG C. at such a partial pressure that silicon monoxide and carbon monoxide are formed with little or no silicon carbide.

Two Source Evaporation of Uniform Thickness, Gallium Arsenide Films

Abstract: Crucible arrangements for two source vacuum evaporation of thin GaAs films of uniform thickness

Aluminum contact deposition and testing for silicon solar cells.

Abstract: Ion beam sputtering, evaporation and electrical degradation of Al contacted Si solar cells observed in high temperature cyclic tests

The morphology of high-rate physical-vapor-deposited Ti and Co

Abstract: Electron-beam high-rate evaporation of hexagonal close packed metals yields highly-orientated vapor-deposited foils The morphology of both titanium and cobalt are shown to be dependent on the deposition parameters A change in deposition rate was found significantly to affect the structure of titanium foils All temperatures and rates gave basal planes parallel to the substrate for the titanium foils A change in substrate temperatures from 500 °C to 8oo °C for the cobalt affected both structure and texturing At 5oo °C, the cobalt was oriented so that the basal plane of the foil was predominantly parallel to the substrate but was changed to about 40 degrees from the substrate at 8oo °C

Investigation of the process of liquid evaporation from a porous metal under vacuum conditions

Abstract: The method and results of an investigation of the evaporation of water into a vacuum are described. The steady-state regime of evaporation in a porous metal is examined. The dependence of the evaporation rate on the parameters of the porous metal and the heat flux density has been experimentally determined. The temperature distribution in the porous plate is determined theoretically.

Improvements in or relating to film resistors

Abstract: 1,137,285. Resistors. WELWYN ELECTRIC Ltd. 8 May, 1967 [23 June, 1966], No. 28085/66. Heading H1S. A resistor comprises an insulating substrate 1 e.g. ceramic, a primary resistance film 2 of e.g. metal oxide such as tin oxide doped with antimony or boron, or tin oxide and a conductive dope mixed with an oxide that fuses to a glaze when fired, or a metal-glaze of palladium or silver and an oxide fusible to a glaze, and a secondary film 3 of resistive material superposed on the primary film, the secondary film being softer and more readily abradable than the primary film to enable adjustment of the resistor to a pre-determined value by abrading part of the secondary film. The secondary film may be evaporated nickel-chromium alloy or sputtered tantalum or gold, other noble metals or their alloys deposited by electroless or evaporation methods or nickel or cobalt or alloys similarly deposited, or an alloy of nickelphosphorus deposited electrolessly. Brass or steel end-caps 4 may have solder-coated copper wire leads 5 welded or soldered on. Abrasion may be carried out by sandblasting, or rubbing with emery cloth, india rubber or tools and fluids comprising silicon carbide and/or diamondgrit. A helical groove of two or three turns may be cut to increase the resistance, in which case abrasion adjacent the grooves gives a coarse adjustment while abrasion on other regions gives a fine adjustment (Fig. 3, not shown). The substrate may be flat. (Fig. 4, not shown) with a meandering resistance track and with metallized terminal areas. The adjusted resistor may be coated with a self-drying or cold-setting organic elastomer e.g. masking lacquer of vinyl or nitrocellulose or cold-setting silicone rubber.