AVS 53rd International Symposium
    Surface Science Tuesday Sessions
       Session SS1-TuA

Paper SS1-TuA7
Impact of Intrinsic Vacancy Ordering on Nanoscale Morphology and Structure: (Group-III)@subx@Se@suby@ on Si(111)

Tuesday, November 14, 2006, 4:00 pm, Room 2002

Session: Surface Structure and Morphology
Presenter: C.Y. LU, University of Washington
Authors: C.Y. LU, University of Washington
T.C. Lovejoy, University of Washington
M.A. Olmstead, University of Washington
F.S. Ohuchi, University of Washington
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Group III-Selenide semiconductors, where III=Al, Ga and In, are both structurally and chemically compatible with silicon, and have potential applications for spintronics and phase change memory devices. They crystallize a variety of bulk structures that incorporate intrinsic vacancies, including layered, defected zinc-blende, and defected wurtzite. Heteroepitaxy allows control of nanostructure morphology by inducing different arrangements of intrinsic vacancies. We report here an in-situ study using scanning tunneling microscopy and photoelectron spectroscopy to elucidate the role of intrinsic vacancies when Group III-Se films are grown on Si(111). Growth of Al@subx@Se@suby@ starts with a stable AlSe bilayer, followed by growth of Al@sub2@Se@sub3@, which forms triangle islands with edges aligned to <1-10> directions of Si(111), consistent with wurtzite Al@sub2@Se@sub3@ (helical vacancy structure). Ga@subx@Se@suby@ also starts with a stable interface bilayer (GaSe), but subsequent growth is layered Ga@sub2@Se@sub2@, with intrinsic vacancies in planes between the layers. For In@subx@Se@suby@, a stable InSe bilayer is not formed. Rather, it keeps the 7x7 substrate registry intact, eventually wetting the surface to form a flat morphology with ~10 nm ~hexagonal domains separated by misfit dislocations, consistent with crystalline @alpha@-In@sub2@Se@sub3@. This is despite the +4% lattice mismatch that might be expected to lead to 3-D island formation.