High Oxidative Conditions Research Articles

Equilibrium Phase Diagrams for Analysis of the Oxidation of III-V Compound Semiconductors

ABSTRACTThe phases which result from the oxidation of III-V compound semiconductors can be predicted from a knowledge of the condensed phase portion of their equilibrium phase diagrams. Examples will be shown for arsenides, antimonides, and phosphides. Use of these diagrams explicitly presumes equilibrium growth conditions, and that assumption often fails. In such cases kinetic rather than thermodynamic factors dominate the determination of the observed phases. Examples of this phenomenon for anodic oxidation will be presented. Recent interest in high pressure oxidation conditions as a means of alleviating kinetic limitations will be discussed for InP. The phase diagrams can also be used to predict interfacial reactions under certain conditions and data for GaAs will serve to illustrate this point.

Composition of siderite and the environments of formation of vein-type deposits in Japan

Electron probe microanalysis data for several siderite specimens from Miocene epithermal vein-type deposits of Au-Ag type (Ohmori mine) and Pb-Zn type (Toyoha mine) in Japan reveal a remarkable contrast in zinc content. Siderite in the Ohmori deposit contains an appreciable amount of zinc, ranging from 0.8 to 5.8 in ZnO weight percent, whereas the zinc content in the Toyoha deposit is less than can be detected by present techniques.How the zinc content of siderite is affected by physicochemical variables such as temperature, oxygen fugacity, and pH has been evaluated theoretically. Applying the results to the analytical data obtained, it is concluded that Au-Ag mineralization took place under relatively high oxidation conditions in comparison with Pb-Zn mineralization. This view is strongly supported by the mode of distribution of iron in sphalerite in these types of mineralization.