IMPURITY-MEDIATED ONE-DIMENSIONAL CRYSTALLIZATION OF THIN AMORPHOUS-GE FILMS ON SI(111)

We have observed peculiar low temperature crystallization dynamics of thin amorphous Ge films deposited on Si (111):7X7 substrates. The one-dimensional geometry and low temperature kinetics of this crystallization indicate an impurity mediated mechanism similar to that suggested by Nygren, McCallum, Thornton, Williams, and Olson [Mater. Res. Soc. Symp. Proc. 100, 403 (1988)]. Interaction is observed between the buried surface structure and the crystallizing Ge film, in some cases resulting in Ge which grows epitaxially not on the bulk Si, but on the 7X7 reconstruction, effectively a two-dimensional substrate.