Crystal forms by solid-state recrystallization of amorphous Si films on SiO2

Abstract

The recrystallization behavior of amorphous silicon films formed by Si + ion bombardment onto polycrystalline silicon films has been studied. Two crystal forms have been identified by transmission electron microscopy and electron diffraction for the first time. Disk-shaped crystals are formed as a result of the presence of {111} twin planes parallel to the film surface. Threefold symmetric crystals are formed by the presence of the three {111} twin planes that are not parallel to the film surface. Their feature looks less dendritic due to restricted space of film thickness in which crystal branches may grow. These two crystal forms have 〈111〉 direction normal to the film surface. A model for the formation of these crystals is proprosed in the process of solid-state recrystallization.