STUDY ON SURFACE AND INTERFACE STRUCTURES OF NANOCRYSTALLINE SILICON BY SCANNING-TUNNELING-MICROSCOPY

The scanning tunneling microscope has been employed to study the morph ology, atomic surface structures, and grain interface of hydrogenated nanocrystalline silicon (nc-Si:H) before and after hydrofluoric acid ( HF) etching. It was found: (1) The nc-Si:H films were composed of many different sizes of grains and these grains were composed of many fine r grains. (2) There were line structures on the surface of the fine gr ains and loop structures at the grain boundaries without HF treatment. After etching, two more structures were observed: loop structures on the surface of fine grains and spider bonding structures besides the i nterface of fine grains. (3) The loop structures found at the grain bo undaries was larger and more irregular than those on the grain surface s. Line structures were similar to crystal silicon, but the distance b etween lines was enlarged. Considering the experimental results, a dis cussion was made about the formation mechanism of these atomic structu res. (C) 1997 American Vacuum Society. [S0734-211X(97)12904-3].