SCANNING TUNNELING MICROSCOPY OF 1-PERCENT-HF-TREATED SI(111) SURFACES

Scanning tunneling microscopy (STM) has been carried out on an as-prepared Si(111) surface by the 1%-HF treatment. On the flat parts with neither adsorbates nor atomic steps, there exist atomic dots with the well-ordered threefold symmetry and the separation of 2.2 angstrom, which originate from the H atoms in the Si(111):SiH3 phase. On the flat parts near the adsorbates, the images are deviated from the well-ordered threefold symmetry and classified into three patterns: the irregular arrangements of atomic dots indicating the presence of the domain boundary, U-shaped dots consisting of three atomic dots, groups of one bright dot and two faint dots with the corrugation difference of 0.5 angstrom. The latter two patterns are 3.8 angstrom in period and exhibit the threefold symmetry, whose features are in accordance with those of Si(111): 1 x 1. These images change continuously from one to another. These results may be explained by extending the Si(111): SiH 3 model.