Growth Mechanisms of Silicon Crystallites Grown on Top of a Metal‐Coated Graphite Substrate

Abstract

Microscopic in situ observations and a posteriori surface topography by means of optical and scanning electron microscopy have been carried out in order to study the growth of large‐grain polycrystalline silicon films from the gas phase onto a graphite substrate coated with a liquid layer of tin or aluminum. In the present study, only the initial stages of the process, where crystal growth is governed by vapor‐liquid‐solid mechanisms, are considered. For the growth of the crystallites in the polycrystalline layers, which occur in two morphological forms, viz., needles and platelets, two different mechanisms could be identified: (i) a twin plane reentrant edge (TPRE) mechanism, leading to a fast lengthwise growth of needles and a fast sidewise growth of platelets; and (ii) a nucleation mechanism, accounting for a slow thickness growth of the needles and a slow expansion of the platelike crystals. On the upper surfaces of some needles and platelets a capricious surface pattern (always in conjunction with the occurrence of some solidified metal droplets) could be identified, which could be interpreted in terms of a two‐dimensional VLS growth mechanism.