Showing papers on "Chemical vapor deposition published in 1971"

Electrical Properties of High‐Quality Stannic Oxide Crystals

Abstract: Single crystals of the wide bandgap semiconductor stannic oxide, SnO2, have been grown and studied electrically. A chemical vapor deposition technique using chlorine transport, no inert carrier gases, and low pressure has been used to grow stannic oxide crystals of higher purity and with almost an order‐of‐magnitude higher low‐temperature Hall mobility, 8800 cm2/V sec at 80°K, than have previously been available. Measurements of Hall mobility, carrier concentration, and resistivity have been made between 20 and 625°K on crystals with room‐temperature carrier concentrations between 8×1015 and 2×1018 cm−3. The effects of the crystal anisotropy on these measurements have been investigated and found to be small (all results reported are for the a direction). A donor level ∼35‐meV deep due to antimony and another level ascribed to oxygen vacancies at ∼140 meV have been observed. Polar optical mode scattering with a dominant characteristic temperature of 1080°C is the main carrier scattering mechanism above 250°K. Below 250°K acoustic deformation potential scattering dominates. Ionized impurity scattering is eventually important in all samples as the temperature is lowered. A polaron effective mass of 0.39 me has been found consistently in the analyses of the data. A technique of fabricating good Schottky barriers on SnO2 has also been developed and used to measure the net donor concentration in samples. The agreement found between these measurements and Nd from Hall measurements indicates that shallow trapping is not a problem in these crystals.

Preparation and Properties of Pyrolytic Zirconium Dioxide Films

Abstract: Zirconium dioxide films in the thickness range of 500–8000Aring; have been prepared by chemical vapor deposition in the temperature range of 800°a 1000° C. The films were identified as fine‐grained (∼325Aa), nearly stoichiometric, monoclinic , using electron microprobe analysis, infrared absorption, and transmission electron microscopy. The films exhibited remarkable resistance to most aqueous acids and bases, although slight etching occurred in hot (220°C) phosphoric acid. The deposits had an index of refraction of and an optical energy gap of 5.12 eV. deposited on silicon offered little resistance to Na diffusion at 600°C, while films deposited on thermal were a good barrier due to pile‐up of the Na near the interface. The current density, , depended on the field, , where was 6 for the metal biased negatively and 2.75 or 5, depending on the magnitude of the field, for the opposite polarity. The dielectric constant in the frequency range of was relatively independent of frequency near 300° K and equal to approximately 18, however some dispersion was noted near 573°K. The a‐c conductivity could be represented by where is the measuring frequency and β a temperature dependent parameter, decreasing from . The dielectric strength of the films varied between , independently of thickness and polarity. High frequency (1 MHz) C‐V measurements indicated the presence of negative surface charge, which varied between . The structures exhibited instability under negative bias, indicative of negative charge being injected into the insulator. C‐V measurements on the double dielectric system showed that the presence of caused a flatband voltage displacement . In addition, the flatband voltage shifted as a function of time under negative bias and was found to obey the relationship .

Chemical vapor deposition in the titanium-carbon system

Abstract: Various forms of titanium carbide single crystals and polycrystalline layers were deposited on graphite substrates from a vapor phase consisting of hydrogen, titanium- and carbon tetrachloride, in the temperature range 1200 °–1600 °C. The correlation between the carbon content of the vapor phase and the solid phase (TiC; TiC + C) was investigated; the influence of the graphite substrate on this relationship was examined. The morphology and properties of the deposition products are described. Octahedral single crystals of titanium carbide, TiC1.00, especially were deposited. Deposition of other phases such as dititanium carbide, Ti2C, titanium dicarbide, TiC2, or any modification of titanium or carbon as a single phase could not be detected. The latter observation contradicts any mechanism by which a pyrolytic carbon deposition is assumed as a first reaction step in the deposition of titanium carbide.

Self‐Healing Breakdown Measurements of Pyrolytic Aluminum Oxide Films on Silicon

Abstract: Self‐healing breakdown techniques are employed to study dielectric breakdown in pyrolytic aluminum oxide films on silicon substrates. The Al2O3 is prepared by chemical vapor deposition at low temperature (300–600°C) using Al isopropoxide as source material. Both weak‐spot breakdown and intrinsic breakdown in the absence of weak spots using Au–Al2O3–Si test capacitors are investigated. Intrinsic breakdown field strengths of 7.5×106 V/cm for Si+ on p‐type substrates and 6.9×106 V/cm for Si − on n‐type are observed and found to be independent of Al2O3 thickness and temperature. Weak‐spot breakdown is found to be associated with contamination of the silicon surface.

Chemical vapor deposition of magnetic garnets for bubble-domain devices

Abstract: Stable magnetic bubbles have been formed and propagated in films of mixed terbium erbium iron garnet, grown by chemical vapor deposition on substrates of samarium gallium garnet and mixed samarium gadolinium gallium garnet. Smooth films were obtained with growth rates of 2-5 μm/h. A 20-μm period Y-bar circuit was deposited on a film of approximate composition Tb 2.5 Er 0.5 Fe 5 O 12 on a Sm 3 Ga 5 O 12

Formation of tungsten and molybdenum carbides

Abstract: THE INVENTION IS FOR METHODS FOR THE FORMATION OF TUNGSTEN AND MOLYBDENUM CARBIDES OR MIXTURES THEREOF, THE METHOD COMPRISING EFFECTIG A VAPOUR PHASE CHEMICAL INTERACTION BETWEEN (1) A METL HEXAFLUORIDE WHEREIN THE METAL IS SELECTED FROM THE GROUPS CONSISTING OF TUNGSTEN, MOLYBDENUM AND MIXTURES THEREOF, (2) A REACTABLE HYDROCARBON AND (3) HYDROGEN, SAID INTERACTION BEING EFFECTED AT REACTION TEMPERATURES BETWEEN 400*C AND 1000*C AND WITH A CARBON TO HYDROGEN RATIO IN THE MIXTURE SUFFICIENTLY LOW AS ENSURE SUBSTANTIALLY NO CARBON IS DEPOSITED AS THE REQUIRED CARBIDE IS FORMED THE METHOD IS GENERALLY EFFECTED AT REACTION TEMPERATURES BETWEEN 500*C AND 900*C IT IS PREFERRED THAT THE REACTION MIXTURE CONSISTS OF TUNGSTEN HEXAFLUORIDE, BENZENE, TOLUENE OR XYLENE AND HYDROGEN THE HYDROCARBON HOWEVER MAY BE ANY ONE OF A WIDE RANGE OF HYDROCARBONS THAT ARE VAPORISABLE AT THE REACTION TEMPERATURES AND WHICH WILL UNDERGO REACTION WITH THE OTHER COMPONENTS TO PRODUCE THE REQUIRED CARBIDE BY THE METHOD OF THE INVENTION THE CARBIDE, ESPECIALLY TUNGSTEN CARBIDE, CAN BE APPLIED TO A WIDE VARIETY OF SUBSTRATES SUCH AS THE WORKING SURFACE OF A STEEL TOOL OR BEARING OR ON CARBON OR BORON FIBRES

Reflector assembly for reflecting the vapors of high temperature volatile materials

Abstract: A vapor reflector assembly disposed in a vapor deposition chamber comprises a thin, fluorinated resin film coated onto a support body and means to heat said film to an elevated temperature.

Semiconductor device having a composite film as a passivating film

Abstract: A semiconductor device having a composite film as a passivating film formed on the surface of the device in the order of films of silicon oxide formed by thermal oxidation, phosphorous glass, silicon oxide formed by chemical vapor deposition and silicon nitride, whereby cracks, which occurs in the film when the phosphorous glass film is in contact with the silicon nitride film, can be eliminated.

Growth and Some Magnetic Properties of GdIG Films

Abstract: The growth and magnetic properties of GdIG films grown by chemical vapor deposition on YIG and GdGaG substrates is described. Various aspects of the deposition technique including the design of a concentric tube reactor, hydrodynamics of the gas flow, substrates, and deposition parameters are discussed in detail. GdIG films have been grown at rates as high as 16 μ/h. They are epitaxial and are of the same orientation as the substrate. The films are strained because of mismatch between the film and substrate. A Faraday effect hysteresigraph has been used to measure the coercive force and the compensation temperature. The remanence has been measured as a function of temperature from −40° to 60°C and has been correlated with strains in the film. Diffusion has been observed between the film and substrate. This can be minimized by increased growth rates and by preheating substrates.

Chemical vapor deposition of steel with tantalum and columbium

Abstract: A process for cladding of steels and the resulting product. A consistent and acceptable bond is obtained by providing a containment coating to prevent diffusion of the ingredients of the substrate into the cladding material. A desirable containment coating is one in which one of the constituents is provided by the substrate to provide a composite which is more stable than similar compounds of the cladding coat such as tantalum or columbium. This permits a chemical vapor deposition of the cladding without adverse reaction with surface ingredients. A further step in the process is available in the localizing of flow of gas in the deposition to bring them together just prior to contact with the shape to be coated.

Behavior of Hydrogen on Nickel

Abstract: Hydrogen adsorption behavior on polycrystalline nickel surfaces, using electron impact desorption flash filament with gas phase and ion spectrometer and vapor deposition

Thermal emissivity and solar absorptivity of aluminum coated with double layers of aluminum oxide and silicon oxide.

Abstract: Thermal emissivity and solar absorptivity of Al coated with surface layers of aluminum oxide and silicon oxide, describing fabrication techniques and performance measurements

Growth of Uniaxial Magnetic Garnet Films by a Simplified Method of Chemical Vapor Deposition

Abstract: Epitaxial films of gallium‐substituted yttrium iron garnet displaying magnetic domains have been grown on gadolinium gallium garnet and mixed gadolinium dysprosium gallium garnet substrates. The films grown on Dy: GGG were crack‐free. A chemical‐vapor‐deposition (CVD) system using metal source materials and a simplified geometry was developed. Investigations were made of several different types of growth which occurred and of the efficiency of HCl transport. Results of these studies, as well as magnetic properties of the films and a description of the CVD system and growth conditions, are presented.

Process for vapor deposition on glassy-carbon substrate

Abstract: Glassy-carbon monofilament containing additional sulfur in combined form, has ''''high-temperature creep'''' properties useful in the deposition of boron, boron carbide, silicon carbide, and pyrolytic graphite thereupon

Secondary electron multipliers with single layer cermet coatings

Abstract: Secondary electron multiplier devices having one or more secondary electron emission multiplier elements each consisting essentially of a single-layer cermet coating on a supporting substrate. The coating may be formed by various techniques including flash evaporation, vacuum sputtering, and chemical vapor deposition. Secondary emission ratios of two, three and more are attained with first cross-over voltages in the range from 20 to 40 volts. In applications where optimum temperature stability is required, gold/metal oxide cermets are employed.

Monitoring of vapor density in vapor deposition furnance by emission spectroscopy

Abstract: The rate of vapor deposition in a vacuum furnace heated by electron bombardment is monitored or controlled. The vapor is ionized, preferably by the same electron bombardment as produces it. The ionized vapor radiates light which is detected at one or more locations within the furnace, preferably by a photomultiplier optically coupled by a light pipe to the interior of the furnace. The light detector produces a signal indicative of the intensity of the light detected and, hence, of the vapor density. Optical filters may be used to pass light of frequency characteristic of particular elements, so that the relative intensity of the particular elements in the vapor may be selectively detected. The signals may be recorded or used to control the heating and, hence, vapor density, as by controlling the electron emission from an electron gun.

Method of producing doped tungsten powders by chemical deposition

Abstract: Method of preparing doped tungsten powders for use in the fabrication of tungsten filament wire by simultaneous chemical vapor deposition of tungsten and dopant. There is also provided the product produced by this process which has a very homogeneous distribution of dopant within individual particles of powder.

Growth of ternary compounds utilizing solid, liquid and vapor phases

Abstract: This disclosure provides a process for obtaining a ternary compound with a particular composition or with continuous range of compositions utilizing steps of a chemical vapor deposition procedure which cannot normally be obtained directly by chemical vapor deposition itself. Through the chemical vapor deposition procedure, a first layer of GaP is deposited epitaxially onto a crystalline substrate; thereafter a layer of InP is deposited on the first GaP layer; and finally another GaP layer is deposited on the InP layer. The layers have especially good metallurgical contact with each other and are essentially free of imperfections at the interfaces. In accordance with the solid-liquid-solid procedure of the prior art, the sandwich structure obtained via the noted chemical vapor deposition procedure is established at a given temperature above the melting point of the InP layer but below the melting point of the GaP layers and equilibrium of the ensemble is established thereat. Thereafter, the temperature of one of the interfaces between the GaP layers and the InP liquid zone is cooled and the resultant GaxIn1 xP layer growth is initiated. Conveniently, a temperature gradient is imposed on the sandwhich structure ensemble and the growth of the GaxIn1 xP layer continues until the GaP layer at the higher temperature is consumed, or the growth thereof is otherwise terminated.

Structure and Topography of Monocrystalline Nickel Thin Films Grown by Vapor Deposition

Abstract: Monocrystalline nickel thin films were grown by vapor deposition onto heated rocksalt substrates. The (100)‐, (110)‐, and (111)‐oriented nickel films were prepared by deposition onto (100)‐, (110)‐, and (111)‐oriented rocksalt substrates, respectively. The structures of the films were examined by x‐ray diffraction and electron diffraction and microscopy. These thin films (less than 1000 A thick) were well oriented and continuous and contained relatively high densities (108−1011/cm2) of stacking faults, twins, and dislocations. Ledges parallel to the 〈001〉 were found on (100)‐oriented films and {111} facets along 〈110〉 were found on (110)‐ oriented films. The (111)‐oriented films were quite rough with pits, mounds, and other ledges. These films were satisfactory for investigations on the initial stages of oxidation and catalysis.

Magnetic oxide films

Abstract: Magnetic oxide films including europium oxide, yttrium and gadolinium iron garnets, orthoferrites, and ferrites are reviewed from a point of view which stresses the common aspects of oxide film growth and the resulting structural and magnetic properties. The growth techniques of each material are described. They include chemical vapor deposition, sputtering, chemical solution, liquid epitaxy, and evaporation. Problems such as non-stoichiometry, strain, cracking, and substrate-film interaction are discussed for each material. The substrate is found to exert a strong influence on the film quality and generally a better match between film and substrate results in improved films. The magnetic characteristics of the films including the magnetization, coercive force, Faraday rotation, and ferromagnetic resonance linewidth are discussed. In terms of these properties, the films are compared with the corresponding bulk materials. The means of improving magnetic oxide films are considered, and an assessment is made of the possibility of producing thin films whose structural and magnetic properties are comparable with those of bulk material.

Method for providing metallic carbide coatings on graphite

Abstract: Metallic or nonmetallic carbide coatings of substantially uniform thickness are provided on internal surfaces of elongated bores within a graphite substrate by vapor deposition. The coating process is achieved by the thermal decomposition of a selected halide and the inter-reaction with a hydrocarbon gas at temperatures of 900 to 1200 deg C. at atmospheric pressure. A temperature gradient along the length of the bore is used to control the coating deposition rate for providing a carbide coating of substantially uniform thickness. (Official Gazette)

Method for producing refractory metal members by vapor deposition,and resulting product

Abstract: Method of preparing tungsten, molybdenum or zirconium members such as can be used in light sources wherein a metallic member has vapor-deposited thereon additional metal by a chemical vapor deposition process. For the process of fabrication of tungsten filament wire, the required dopants can also be chemically vapor deposited in the desired concentration. There is also provided the product produced by this process. The method of chemical vapor deposition of members is particularly adapted to continuous production techniques wherein after deposition, the member is mechanically reduced to its original cross-section area and wherein a portion of the mechanically reduced material has deposited thereon additional material to provide a continuous chemical vapor deposition method preparation.

Process for chemical vapor deposition of zirconium carbide

Abstract: Deposition of zirconium carbide on a substrate is advantageously effected by reacting zirconium and methyl iodide under heating. The deposition of zirconium carbide is useful for coating of a rocket nozzle surface, coating of granular fuels for gas cooled nuclear reactor and the like.