Phase Transformations in Eutectic Gold-Silicon Alloys on Single-Crystal Silicon

Abstract

Phase transformations in eutectic gold‐silicon alloy thin films on single‐crystal silicon substrates have been studied as a function of the rate of cooling from the melt by utilizing metallography, resistivity measurements, and x‐ray and electron diffraction. Cooling at rates <103 °C/sec results in the eutectic structure, which becomes finer with increased rate of cooling. The silicon is found to nucleate and grow epitaxially from the substrate silicon with different shapes and orientations depending on the orientation of the substrate. At cooling rates >103 °C/sec the eutectic transformation is suppressed, and metastable structures are obtained. Isothermal annealing studies show that the reversion of the metastable structures on heating occurs via a series of both diffusionless and diffusion‐controlled transformations.