AVS 45th International Symposium
    Surface Science Division Monday Sessions
       Session SS-MoP

Paper SS-MoP15
Selective Chemical Reaction of HBO@sub 2@ Molecules on the Si(111)-7x 7 Surface Studied by Scanning Tunneling Microscopy

Monday, November 2, 1998, 5:30 pm, Room Hall A

Session: Surface Science Division Poster Session
Presenter: K. Miyake, University of Tsukuba, and CREST, Japan
Authors: K. Miyake, University of Tsukuba, and CREST, Japan
K. Hata, University of Tsukuba, and CREST, Japan
R. Morita, Hokkaido University, and CREST, Japan
M. Yamashita, Hokkaido University, and CREST, Japan
H. Shigekawa, University of Tsukuba, and CREST, Japan
Correspondent: Click to Email
The formation process of boron (B) induced @sr@3x@sr@3 structure by HBO@sub 2@ irradiation was studied by scanning tunneling microscopy (STM). In the chemical reaction of HBO@sub 2@ molecules with Si(111)-7x7 surface, change in the charge density on the adatoms of the 7x7 units during the process play an exceedingly important role, which was analyzed by the bias dependence of STM images, i.e., the adatoms with less charge density become darker in the filled state STM image.@footnote 1,2@ The molecules preferentially reacted with the center adatoms in the unfaulted half units first. This result indicates that HBO@sub 2@ molecules tend to react with the adatoms in less charge density. The center adatoms surrounding the reacted center adatoms became darker compared to those in the normal 7x7 units in the filled state STM images, which indicates some charge redistribution occurred by the reacted center adatoms. Such charge redistribution is supposed to increase the chemical reactivity of the modified center adatoms because HBO@sub 2@ molecules prefer to react with adatoms in less charge density. In fact, center adatoms in the faulted half units, which were adjacent to the firstly reacted center adatoms, reacted subsequently with the HBO@sub 2@ molecules. According to this process, chain structures were formed by the reacted center adatoms. With further irradiation, B atoms were found to form an 1-dimensional network with the same @sr@3x@sr@3 phase, resulting in the formation of an ordered @sr@3x@sr@3 surface. Small off-phase @sr@3x@sr@3 domains remained only in the areas occupied by Si atoms. The remaining Si adatoms were replaced by B atoms with further deposition of HBO@sub 2@ molecules, and a completely ordered @sr@3x@sr@3 surface was formed. @FootnoteText@ @footnote 1@K. Miyake et al., Appl. Phys. Lett. 66, 3468 (1995). @footnote 2@K. Miyake et al., Surf. Sci. 357-358, 464 (1996).