Showing papers on "Oxide published in 1981"

Oxidation kinetics of TiN thin films

Abstract: We have investigated the oxidation kinetics of TiN thin films in dry O2 in view of a possible application of TiN as material for gate electrodes and interconnections in large‐scale integrated circuits. We found that in the temperature range of 500 to 650 °C the oxidation is thermally activated with an activation energy of 2.05±0.05 eV. Thereby the diffusion of oxygen through the oxide is the rate‐limiting process. Analysis with x rays indicates that dry oxidation transforms TiN to the rutile form of TiO2. Films of TiO2 formed in such a manner are found to be semi‐insulating with resistivities in the order of 106 Ω cm and at higher applied electric fields the injection of space‐charge–limited currents is observed.

The effects of water on oxide and interface trapped charge generation in thermal SiO2 films

Abstract: Water was diffused into very dry thermal SiO2 films under conditions such that the penetration of water related electron trapping centers was of the order of the oxide thickness. In both dry oxides and water diffused oxides, production of negative bulk oxide charge Qot and positive interface charge Qit by an avalanche‐injected electron flux was observed. The efficiencies of both processes were enhanced by water indiffusion. Analysis of the kinetics of charge generation indicated that production of trapped electron centers (Qot ) was required for subsequent production of interface states and charge (Qit ). Models for both processes are discussed. We suggest that inelastic collisions of conduction electrons with the trapped electron centers releases mobile hydrogen atoms or excitons. The mobile species migrate to the Si–SiO2 interface and form states and fixed charge.

Oxidation Kinetics of Hot‐Pressed and Sintered α‐SiC

Abstract: The oxidation kinetics of sintered α- and hot-pressed SiC were investigated over the temperature range 1200° to 1500°C. Oxide thicknesses were measured by ellipsometry, interferometry, and profilometry. The two materials behaved similarly, exhibiting parabolic behavior for short times (up to 100 min) followed by decreasing rates for longer times. The oxidation rates for the sintered material were lower than for the hot-pressed material at all temperatures studied. Apparent activation energies varied with temperature, from 134 to 389 kJ/mol for the sintered alpha material and from 155 to 498 kJ/mol for the hot-pressed variety. Platinum-marker experiments indicated that new oxide is formed at the silicon carbide/ oxide interface. It is proposed that the diffusion of oxidant through the growing oxide film is the rate-controlling process. The details of the oxidation kinetics were complicated by the partial crystallization of the oxide film at higher temperatures, leading to complex paths for transport of oxidant through the film so that the apparent activation energies are difficult to interpret.

Adsorption From Aqueous Solutions

Abstract: The Power Exchange Function: A General Model for Metal Adsorption onto Geological Materials.- The TiO2/Aqueous Electrolyte System - Applications of Colloidal Models and Model Colloids.- Effects of Strong Binding of Anionic Adsorbates on Adsorption of Trace Metals on Amorphous Iron Oxyhydroxide.- Specific Adsorption of Co(II) and [Co(III)EDTA]- Complexes on Hydrous Oxide Surfaces.- The Adsorption of Alkaline-Earth Metal Ions at the Rutile/Aqueous Solution Interface.- The Adsorption of Oleate from Aqueous Solution onto Hematite.- Adsorption of Polyacrylamide and Sulfonated Polyacrylamide on Na-Kaolinite.- Interaction of Pesticides with Chitosan.- Interaction of Zinc Ions with Hydroxylapatite.- Sorption of Actinides from Aqueous Solutions Under Environmental Conditions.- Surface Chemistry and Adsorption Properties of Milled Chrysotile Asbestos Fibres.- X-Ray Photoelectron Spectroscopic (XPS) Studies on the Chemical Nature of Metal Ions Adsorbed on Clays and Minerals.

Chemisorption and oxide formation on metals: Oxygen–nickel reaction

Abstract: The reaction of oxygen with atomically clean nickel surfaces is reviewed. The reaction consists of three stages—chemisorption, oxide nucleation and lateral growth to coalescence, and thickening of coalesced oxide. Chemisorption is dissociative and nonreconstructive in general. However, a reconstructed chemisorbed phase is detected on Ni (110). NiO nucleates and grows laterally as islands displacing the chemisorbed phase, and finally coalescing to passivate the nickel surface. The conditions and rates at which the coalesced oxide thickens have not been well defined.

Coloured materials and photoluminescence centres in anodic film on aluminium

Abstract: Anodic oxide films formed on aluminium in lower aliphatic carboxylic acids exhibit self-colouring of yellow through brown, and characteristic properties such as photoluminescence (PL), electroluminescence (EL), and electron spin resonance (ESR). These phenomena are closely associated with the carboxylate species incorporated in the oxide during anodization1. Although the presence of incorporated carboxylate species in some cases2,3 and their distribution in oxalic acid film have been established4, there have been little data available on the state of incorporated impurities in the oxide. We have studied the distributions of coloured material and PL centres in the oxide and report here that most of the coloured material is located in the outer region of the cell walls of an oxalic acid film, but that the PL centres are in the middle region and have different properties from those of the outer region. These results suggest that the incorporated impurities which are present in the various states in oxide have to be converted during anodization.

Chemical composition and formation of thermal and anodic oxide/III–V compound semiconductor interfaces

Abstract: The literature on the chemical composition and growth of thermal and anodic oxides of the Ga and In III–V compounds is reviewed and discussed. Emphasis is placed on the questions ’’what is the chemical composition of the oxide/III–V interface’’ and ’’how and why did it get that way’’. It is apparent that much is known about these interfaces but knowledge of a number of important growth, thermodynamic, and structural parameters is lacking.

Modification of tunneling barriers on Nb by a few monolayers of Al

Abstract: We report that the normal-state tunneling behavior of Nb\char22{}oxide\char22{}Ag junctions is radically changed when very thin Al is deposited over the Nb before oxidation. From measurements of the oxidation rate, the conductance at high bias, the zero-bias anomaly, and observations of molecular excitations, we show that behavior generally associated with tunneling through niobium oxide disappears when the Al thickness is about two monolayers.

Ruthenium‐Based Mixed Oxides as Electrocatalysts for Oxygen Evolution in Acid Electrolytes

Abstract: Ruthenium oxide, prepared by the thermal decomposition method, has the highest known initial electrocatalytic activity for oxygen evolution in acid electrolyte. However, this material is not stable in the electrolyte and at the same time exhibits a significant increase of oxygen overpotential with time, probably due to a chemical transformation of the oxide from a lower to a higher valence state. Efforts were made to stabilize ruthenium by preparing mixed oxides with Ir and/or Ta using the thermal decomposition method. The electrocatalytic activities for oxygen evolution on these oxides in were determined using the potentiostatic method. The surface areas of these oxides were estimated using cyclic voltammetry. Dual Tafel slopes (approximately 30 and 40 mV) were found on most of these oxides. The ternary oxide exhibited a single Tafel slope of 30 mV, had the lowest overpotential, and showed minimum variation of overpotential with time.

Formation of sidewall oxide layers by reactive oxygen ion etching to define submicron features

Abstract: This invention involves the defining of a submicron feature (21 or 93) in a structure, typically an insulated gate field effect transistor structure (30, 40, or 110). This feature is defined by a sidewall oxide protective masking layer (21 or 71) formed by reactive oxygen ion etching of the structure being built at a time when an exposed surface thereof in the vicinity of the sidewall contains atoms of a material--for example, silicon or aluminum--which combine with the oxygen ions to form the sidewall oxide layer.

Carbon-reinforced metal-matrix composites

Abstract: A carbon fiber reinforced metal matrix composite is produced by metal oxide coating the surface of the fibers by passing the fibers through an organometallic solution followed by pyrolysis or hydrolysis of the organometallic compounds. The metal oxide coated fibers so produced are readily wettable without degradation when immersed in a molten bath of the metal matrix material.

The Growth of Oxidation Stacking Faults and the Point Defect Generation at Si ‐ SiO Interface during Thermal Oxidation of Silicon

Abstract: A general relation for the growth and retrogrowth of oxidation‐induced stacking faults (OSF) has been developed with three key observations from OSF experiments: (i) the growth rate of OSF is independent of their size and density, (ii) the ambient, pressure, and time dependences are explained by an oxidation rate dependence of the supersaturation of silicon self‐interstitials in silicon which induces the fault growth, and (iii) the shrinkage of the faults in inert or oxidizing ambients is controlled by the same mechanism with activation energy of ~4.8 eV. To explain the oxidation rate dependence of interstitial supersaturation, a two‐step oxidation model is proposed. In the first step, the lattice silicon atoms near the interface oxidize to form, but leave a substantial number of silicon atoms as interstitials near the interface. In the second step, these excess silicon atoms flow interstitially mostly into the oxide where they react with oxygen atoms until the oxidation is essentially complete, while a small fraction flows into the bulk silicon. The balance of the reactions in the two steps determines the silicon interstitial supersaturation in silicon which controls the growth rate of OSF. The correlation between the OSF and other oxidation‐induced phenomena, e.g., oxidation‐enhanced diffusion (OED), and oxide fixed charge, , formation is also discussed based on the model. The correlation supports the postulate that these phenomena are caused by oxidation via the same point defect mechanism.