SELECTIVE CHEMICAL-REACTION OF HBO2 MOLECULES ON THE SI(111)-7X7 SURFACE STUDIED BY SCANNING-TUNNELING-MICROSCOPY

In the chemical reaction of HBO2 molecules with Si(111)-7 X 7 surface, change in the charge density on the adatoms of the 7 X 7 units during the process was found to play an exceedingly important role. The mole cules preferentially reacted with the center adatoms in the unfaulted half units first. In the filled state STM images, the center adatoms s urrounding the reacted center adatoms became dark compared to these in the normal 7 X 7 units, which indicates existence of some charge tran sfer caused by the reacted center adatoms. Since HBO2 molecules tend t o react with the adatoms in less charge density, such charge redistrib ution is supposed to increase the chemical reactivity of the modified center adatoms. In fact, center adatoms in the faulted half units, whi ch were adjacent to the firstly reacted center adatoms, reacted subseq uently with the HBO2 molecules. According to this process, chain struc tures were formed by the reacted center adatoms, which may be related to the B network structure previously observed. (C) 1998 Elsevier Scie nce B.V. All rights reserved.