Polytypism and Amorphousness in Silicon Whiskers

Abstract

New form silicon crystalline whiskers with polytypism have been grown by thermal decomposition of silane in an argon atmosphere at around 500°C on the gold plated surface of silicon crystal. Each whisker has a straight filamentary shape less than 1000 Å in diameter and several hundred microns in length for 40 minutes operation. It was found from the electron diffraction patterns that most of them can be deduced as having a 6H structure (hexagonal, a =3.84 Å and c =18.59 Å). Besides, the existence of some long-period structures was discovered on the diffraction patterns though they are not very common. A whisker grown at above 520°C has an outer crust of amorphous silicon. Raising the growth temperature converts these whiskers into fully amorphous ones. At above 800°C, normal whiskers with a diamond structure have been obtained. The structure of the amorphous whisker grown at intermediate temperature range can be accounted for by the mixture of diamond type and 6H type micro crystals.