Structual Changes of Arsenic Silicate Glasses with Heat Treatments

Abstract

Silicate glass containing arsenic as a diffusant into silicon was studied. The glass was deposited on a heated silicon substrate in the atmosphere of mixture of tetra-ethyl ortho-silicate vapor, arsenic trichloride vapor and oxygen gas between 500–700°C. The structure of the glass and its changes with heat treatments in the atmosphere of oxygen, hydrogen, nitrogen gas and in vacuum were studied by infra-red spectroscopy, electron diffraction analysis and so on. Density, mole percentage of As2O3 and refractive index were also measured. By the heat treatment in hydrogen gas, As2O3 in glass is easily reduced to As and after its treatment, As is oxidized again to As2O3 by the heat treatment in oxygen gas. During a long time heat treatment in oxygen gas, the surface of the glass is crystallized. The damage of the glass by the heat treatment in oxygen gas may be explained by the low softening point and large thermal expansion coefficient of this glass.