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) wi thout hydrofluoric acid etching under atmospheric conditions. Images f rom submicrometer scale down to atomic scale have been represented. On a large scale, the nc-Si:H films are found to be consisted of microcr ystallites separated by different interfacial regions from STM results . The mean size of microcrystallites is about 3-5 nm, which is in agre ement with high-resolution electron microscopy studies. In addition, n ear-atomic resolution STM images provide some information on the inter facial region, which seems to be crucial for the atomic structure and many properties of nanocrystalline materials. The results show that th e arrangements of the atoms on nanocrystallites are well ordered, whil e atoms in the interfacial regions are randomly distributed. The mecha nism for imaging nc-Si:H is discussed.