AVS 47th International Symposium
    Surface Science Thursday Sessions
       Session SS2+VT-ThM

Paper SS2+VT-ThM10
Chlorosilane Adsorption on Clean Si Surfaces: STM and FT-IR Studies

Thursday, October 5, 2000, 11:20 am, Room 209

Session: Adsorption and Desorption Phenomena II
Presenter: M. Nishizawa, Joint Research Center for Atom Technology (JRCAT), Japan
Authors: M. Nishizawa, Joint Research Center for Atom Technology (JRCAT), Japan
T. Yasuda, Joint Research Center for Atom Technology (JRCAT), Japan
S. Yamasaki, Joint Research Center for Atom Technology (JRCAT), Japan
M. Shinohara, Research Institute of Electrical Communication (RIEC), Japan
Y. Kimura, Research Institute of Electrical Communication (RIEC), Japan
M. Niwano, Research Institute of Electrical Communication (RIEC), Japan
Correspondent: Click to Email
Understanding the interaction of silane and chlorosilane molecules, (SiH@sub n@Cl@sub 4-n@), with Si surfaces is the base for atomic-scale control of Si growth. A Si(111) surface exhibits the DAS structure which has 7 kinds of dangling bonds with different electron occupancy, while a Si(100) surface reconstructs to the asymmetric-dimer structure. We are interested in the interaction of chlorosilane with these qualitatively different surfaces. This paper discusses structures of SiH@sub 2@Cl@sub 2@-chemisorbed Si(111)-(7x7) and Si(100)-(2x1) surfaces. We have employed STM to identify reaction sites, and FT-IR to probe their local structure. In the STM topographs for adsorption on the Si(111)-(7x7) surface, reacted adatom sites appear darker than the unreacted ones. At a low coverage, we find that SiH@sub 2@Cl@sub 2@ molecules preferentially react with corner adatoms in the unfaulted half of the (7x7) unit cell to produce surface species - SiH@sub 2@Cl and -Cl. Komura et al. proposed a structural model in which the - SiH@sub 2@Cl group is adsorbed on the corner-hole atom.@footnote 1@ Our STM results agree with this model. On the other hand, FT-IR spectra measured for this surface showed two sharp peaks at 2108 cm@super -1@ and 2123 cm@super -1@. These peaks are tentatively assigned to the symmetric and asymmetric Si-H stretching vibrations of the surface - SiH@sub 2@Cl group. However, the observed peak positions of the Si-H stretching vibrations are much lower than those predicted from the semi-empirical formula by Locovsky.@footnote 2@ The reason for this discrepancy is under consideration. Results for the Si(100) surface will be reported at the presentation. This study, partly supported by NEDO, was performed at JRCAT under the joint research agreement between NAIR and ATP. @FootnoteText@ @footnote 1@ T. Komura et al., Appl Surf. Sci. 130 (1998) 23. @footnote 2@ G. Lucovsky, Solid State Commun. 29 (1979) 571.