AVS 46th International Symposium
    Surface Science Division Wednesday Sessions
       Session SS-WeP

Paper SS-WeP16
Dissociative Reaction of HBO@sub 2@ Molecules on Si(111)-7x7 Surface Studied by Scanning Tunneling Microscopy

Wednesday, October 27, 1999, 5:30 pm, Room 4C

Session: Poster Session
Presenter: K. Miyake, University of Tsukuba, Japan
Authors: K. Miyake, University of Tsukuba, Japan
T. Kaikoh, University of Tsukuba, Japan
Y.J. Li, University of Tsukuba, Japan
H. Shigekawa, University of Tsukuba, Japan
Correspondent: Click to Email
Boron (B) has been attracting considerable attention as a promising c andidate for the formation of atomic-layer doped structure. Atomic-layer dop ing process on Si substrate consists of two parts; adsorption of a monolayer fraction of dopant atoms on Si surface and subsequent Si growth. Therefore, precise control of B atoms on Si surface is essentially important. Recently, HBO@sub 2@ molecules were found as a most appropriate boron source because o f its higher vapor pressure compared to the metal boron cases. However, how HBO@sub 2@ molecules react with the Si surface still remains as an open ques tion. In order to clarify this point, we characterized the chemical reaction process of HBO@sub 2@ molecules on Si(111)-7x7 surface in detail. We succeed ed in confirming two different states of HBO@sub 2@ molecules on the surface . When the substrate temperature during HBO@sub 2@ irradiation was kept at 3 00°C, the adsorbed HBO@sub 2@ molecules remained on the surface witho ut dissociation. On the other hand, when the substrate temperature was kept at 600°C, HBO@sub 2@ molecules were dissociated, and the oxygen- and boron-related adatoms were produced at corner and center adatom sites in 7x7 units, respectively. Taking the difference in the electronegativity between the oxygen and boron atoms into consideration, oxygen and boron atoms in HBO @sub 2@ molecules are expected to react with adatoms and rest atoms, respect ively. Then, as a result of the dissociation of HBO@sub 2@ molecules, oxygen and boron atoms may adsorb at the corner and center adatom sites, respective ly. In order to confirm this reaction process, the sample formed by HBO@sub 2@ irradiation at 300°C was annealed at 600°C for 1min. As exp ected, non-reacted HBO@sub 2@ molecules disappeared and the oxygen- and boro n-related adatoms were observed after annealing. These results indicate high controllability of chemical reaction process of HBO@sub 2@ molecules on Si(1 11)-7x7, and high potential exists in this system. @FootnoteText@ http://dora.ims.tsukuba.ac.jp