Electron microscopy of nucleation and growth of indium and tin films

Abstract

The results of measurements of island density and grain size variations as a function of film thickness and substrate temperature of vapour-deposited indium and tin films are given. It was observed that the nucleation and growth characteristics of indium and tin films are different even when the substrate temperatures are in the same ratio of their melting points. These differences are ascribed to the differences in interfacial surface energy, nucleation barrier, and critical thickness. The saturation density of indium was found to be 2 × 10¹¹ cm⁻² at 85°C while that of tin was 4 × 10¹¹ cm⁻² at 130°c. Island density curves systematically illustrate the occurrence of primary, secondary, and tertiary nucleation. This feature is also apparent from transmission and scanning electron micrographs of films deposited at 130°c. The presence of broad peaks in island density curves and dips in average grain size curves is due to the formation and growth of secondary nucleated islands. The spherical shape of the islands in films deposited at 130°c strongly suggests that the films recrystallize from liquid drops after supercooling.