AVS 45th International Symposium
    Selected Energy Epitaxy Topical Conference Thursday Sessions
       Session SE-ThM

Invited Paper SE-ThM10
Site-Selective Reaction of Br@sub 2@ with the Second Layer Ga Atoms on the As-rich GaAs(001)-2x4 Surface

Thursday, November 5, 1998, 11:20 am, Room 327

Session: In Situ Characterization and Real-Time Diagnostics of Surface Growth Processes
Presenter: A.C. Kummel, University of California, San Diego
Authors: Y. Liu, University of California, San Diego
A.J. Komrowski, University of California, San Diego
A.C. Kummel, University of California, San Diego
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The top layer of the GaAs(001)-2x4 surface consists of rows of As-As dimers while the second layer has exposed Ga atoms between the arsenic rows. Using scanning tunneling microscopy (STM), we have observed that in the initial adsorption stage monoenergetic Br@sub 2@ molecules (0.89 eV) react exclusively with the second layer Ga atoms exposed in trenches or at defects on the As-rich GaAs(001)-2x4 surface. This gallium-selective chemisorption indicates that bromine molecules preferentially react with exposed atoms which have the least filled dangling bonds regardless of their layer. Both abstractive and dissociative chemisorption of Br@sub 2@ molecules are observed to be surface-site selective. The abstractive chemisorption of Br@sub 2@ molecules formed isolated gallium monobromides at As atomic vacancies, As-As dimer vacancies, and in trenches. However, the dissociative adsorption of Br@sub 2@ molecules forms paired gallium monobromdies at As-As dimer vacancies and in trenches. Dissociative adsorption of a Br@sub 2@ molecules in a trench is orientation-specific and results in two GaBr species on the opposites sides of the trench.