MICROSTRUCTURE OF NANOSIZE HYDROGENATED CRYSTALLINE SILICON STUDIED BY SCANNING-TUNNELING-MICROSCOPY

The morphology of nanosize hydrogenated crystalline silicon (nc-Si:H) films have been investigated by scanning tunneling microscopy (STM) without hydrofluoric acid etching under atmospheric conditions. Images from submicrometer scale down to atomic scale have been represented. On a large scale, the nc-Si:H films are found to be consisted of microcrystallites separated by different interfacial regions from STM results. The mean size of microcrystallites is about 3-5 nm, which is in agreement with high-resolution electron microscopy studies. In addition, near-atomic resolution STM images provide some information on the interfacial region, which seems to be crucial for the atomic structure and many properties of nanocrystalline materials. The results show that the arrangements of the atoms on nanocrystallites are well ordered, while atoms in the interfacial regions are randomly distributed. The mechanism for imaging nc-Si:H is discussed.