Formation of nanocrystallites governed by the initial stress in the ultrathin hydrogenated amorphous silicon films

Abstract

Spectroscopic ellipsometry identified E1 transitions at a lower energy than that for c-Si (3.38 eV). These transitions are generated from the Si paracrystallites or disordered crystallites in the ultrathin silicon films (2–10 nm) deposited by thermal chemical vapor deposition. During the growth of the film, paracrystallites expand gradually; disorder in the paracrystallites increases. Finally, a completely disordered Si network, i.e., the amorphous network, is generated. The presence of disorder crystallites in the ultrathin Si films acts as a constraint for the crystallization of the ultrathin films by rapid thermal annealing.