Growth kinetics and morphologies of iron silicide layers

Abstract

The production of iron silicide layers by the vapour deposition of silicon on to iron has been studied over the temperature range 800 to 1200° C. Silicon was deposited from silicon tetrachloride by either a combination of hydrogen reduction and replacement reaction with the iron substrate or by the replacement reaction alone. In the combined process, at temperatures in the range 800 to 1100° C, the deposition occurs by at least 75% hydrogen reduction. At temperatures above 1100° C the rate of the replacement reaction increases more rapidly than that of the hydrogen reduction process, and so the replacement reaction accounts for more than 25% of the overall depostion. The growth morphologies of the layers have been studied as a function of deposition temperature by scanning electron microscopy. The morphologies obtained in the combined process are shown to agree with general predictions based on the effects of gas phase supersaturation on vapour growth morphologies. The deposits produced by replacement alone are shown to vary from having a vapour-etched crystalline morphology to having a flat porous morphology as the deposition temperature is increased.