Grain size control by means of solid phase crystallization of amorphous silicon

The grain size of thermally crystallized a-Si films is controlled by the rates of nucleation, r_N, and growth, r_G, according to the standard Avrami theory. Despite this evidence, most papers devoted to improving the crystallized grain size analyze their results with a qualitative reference to this theory. In this paper, we will show that it is possible to identify the standard set of rN and rrj values for a-Si and that experiments reveal that deviations from these values always result in a smaller grain size. It is also shown that no substantial improvement with non-conventional heat treatments can be expected. Finally, it is argued that a larger grain size is expected from a-Si films containing, in their as-grown state, a controlled density of embedded nanocrystals.