The role of size effects on the crystallization of amorphous Ge in contact with Bi nanocrystals

The kinetics of metal-induced crystallization of amorphous Ge in contact with Bi nanocrystals (NCs) have been studied by in situ transmission electron microscope annealing. Series of nanostructured films consisting of layers of Bi NCs in an amorphous Ge matrix have been grown by pulsed laser deposition. The a-Ge crystallization temperature depends strongly on both the size and shape of the NCs and the separation between the NCs in the film-normal direction. The size of the NCs controls the crystal nucleation process through the amount of metal surface in contact with the semiconductor, the shape of the NCs determines the initial Ge crystallization in the direction perpendicular to the film plane, and the separation between the NCs in the film-normal direction controls the overall pattern of the Ge crystal growth process.