An investigation was made of the (111)-(7 x 7) surface by using a low-temperature non-contact atomic force microscope. Two types of atomic force microscope image, with and without an additional structure between the corner and center adatoms, were obtained. The distance between the corner adatom and the additional structure was 0.7nm. This was not consistent with that (0.43nm) between the corner adatom and the rest atom. It was suggested that the additional structure which was observed was an artefact. A model was proposed in order to explain these results. It was based upon an atomic arrangement of a Si tip apex with an asymmetrical ad-dimer, and the (111)-(7 x 7) surface.

Artefact and Fact of Si(111)-7x7 Surface Images Observed with a Low-Temperature Non-Contact Atomic Force Microscope. N.Suehira, Y.Sugawara, S.Morita: Japanese Journal of Applied Physics - 2, 2001, 40[3B], L292-4