Initial adsorption process of Si atoms on an Si(111)7x7 surface studied byscanning tunneling microscopy

Using variable-temperature scanning tunneling microscopy (VT-STM), the init ial stage of the Si absorption process on an Si(111)7 x 7 surface has been investigated at 80 to 500 K. At room temperature, tetramers were formed ove r the center dimers in the DAS model of the 7 x 7 structure. However, at lo w temperatures these tetramers were formed over the corner dimers. It is su ggested that the mode of Si absorption process changes depending on the tem perature. Many other absorbed Si atoms, which were not used for the tetrame r formation, were diffused over an absorption region. The size of the regio n is strongly related to the sample temperature. The diffusion of Si atoms on the surface was examined using a novel atom-tracking technique. (C) 2000 Elsevier Science B.V. All rights reserved.