AVS 49th International Symposium
    Surface Science Thursday Sessions
       Session SS+EL-ThM

Paper SS+EL-ThM1
Strain Control of the Ge(105) Surface via Hydrogen Adsorption

Thursday, November 7, 2002, 8:20 am, Room C-110

Session: Structure of Semiconductor Surfaces & Interfaces
Presenter: Y. Fujikawa, Tohoku University, Japan
Authors: Y. Fujikawa, Tohoku University, Japan
M. Kawashima, Tohoku University, Japan
T. Nagao, Tohoku University, Japan
T. Sakurai, Tohoku University, Japan
M.G. Lagally, University of Wisconsin-Madison
Correspondent: Click to Email
Controlling the size and shape of Ge quantum dots formed on the Si(001) substrate is of great technological importance for their potential application in future semiconductor devices. Surfactant effects on this system are regarded as a promising method to achieve the controlled growth of quantum dots. Among them, hydrogen adsorption, which has been studied intensively, is known to suppress the formation of Ge "huts", pyramidal nanocrystals bounded by four Ge{105} facets.@footnote 1@ We have investigated hydrogen adsorption on a Ge(105) surface formed on a Si(105) substrate using STM to elucidate the role of surface strain on the stability of Ge(105) under hydrogen-adsorption conditions. The STM images of Ge(105) surfaces with adsorbed hydrogen atoms are understood based on the newly-established atomic structure of Ge(105).@footnote 2@ We observe the stability of hydrogen-covered Ge(105) for different amounts of Ge initially deposited on the Si(105) surface. We find that hydrogen adsorption on Ge(105) surfaces formed from deposited amounts of Ge less than 1.5 ML makes the surface remarkably unstable and results in the formation of local defects. This fact indicates that hydrogen adsorption on Ge(105) increases the surface strain by arresting the strain-relief mechanism that would ordinarily occur on clean Ge(105) with the formation of sp@super 2@-hybridized dimers. Thus, the formation of Ge(105) will be unfavorable and suppressed in the presence of adsorbed hydrogen. This work is supported by NSF. @FootnoteText@ @footnote 1@ Kahng et al., Phys. Rev. Lett. 80, 4931 (1998). @footnote 2@ Fujikawa et al., Phys. Rev. Lett. 88, 176101 (2001).