Modification of the density of crystallites in silicon nano-crystalline thin films by substrate profiling

Abstract

In this paper we describe the production of nanocrystallites of silicon embedded in an amorphous silicon matrix by Hot Wire CVD. Prior modification of the substrate results in a procedure for increasing the volume fraction and density of the nano-crystallites relative to the other phases. A macroscopic process, random linear grooving, applied to the substrates has been shown to have a significant affect on the structure of the thin film nano-crystalline silicon subsequently grown on these profiled substrates. This has been found to occur for samples produced under different temperature regimes resulting in crystalline fractions in the range of 10% to 80%. Analysis of the RAMAN spectra for these samples shows a reduction in the amorphous fraction while the fractions of both the crystalline material and the intermediate phase increase. Electron micrographs show increased crystallite size. The films on the modified substrates appear to be denser than the films on the smooth substrates.