Secondary Grain Growth in Thin Films

Abstract

AbstractNormal grain growth in thin films leads to columnar grains with sizes roughly equal to the film thickness. In subsequent grain growth, a minor fraction of the grains continue to grow at appreciable rates, leading initially to a bimodal grain size distribution and ultimately to a monomodal distribution of grains with sizes much larger than the film thickness. Those grains which continue to grow, secondary grains, often have uniform or restricted texture, suggesting that in such cases surface energy minimization plays an important role in driving their preferential growth. Surface-energy-driven secondary grain growth can, in principle, lead to single crystal films. Turnbull and co-workers were among the first to apply rate theory to the analysis of grain boundary motion, grain growth, and recrystallization. These models have been adapted to describe surface-energy-driven secondary grain growth in thin films. Recent experiments on secondary grain growth in thin metallic and semiconductor films are reviewed. It has been shown that film thickness, film composition and surface topography have pronounced effects on growth rates, final grain sizes and orientations.