SCANNING TUNNELING MICROSCOPE OBSERVATIONS OF SI(111)3X1-AG AND 6X1-AG STRUCTURES

Using scanning tunneling microscopy, we have studied the Si(111)3 x 1- Ag and 6 x 1-Ag structures. The 3 x 1-Ag structure has been observed t o consist of a bright row and two small protrusions. The bright row po ints in the [1BAR10] directions, and the protrusions incline about 10- degrees from the [112BAR] directions, resulting to point in the diagon al directions of the 3 x 1 unit meshes. We found that the 6 x 1-Ag str ucture consists of alternative arrangements of two kinds of 3 x 1-Ag s tructures of which the protrusions incline about + 10-degrees and - 10 -degrees from the [112BAR] directions, respectively. Possible structur al models for the 3 x 1-Ag and 6 x 1-Ag are proposed, based on the pre sent STM results.