AVS 51st International Symposium
    Surface Science Wednesday Sessions
       Session SS2-WeM

Paper SS2-WeM6
Vacancy Induced Nano-Wire Structure of Ga@sub 2@Se@sub 3@ on Si(100)

Wednesday, November 17, 2004, 10:00 am, Room 210C

Session: Semiconductor Surface and Interface Structure
Presenter: T. Ohta, University of Washington
Authors: T. Ohta, University of Washington
D.A. Schmidt, University of Washington
C.Y. Lu, University of Washington
Q. Yu, University of Washington
M.A. Olmstead, University of Washington
F.S. Ohuchi, University of Washington
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We report formation of nano-wire structure of gallium-selenide (Ga@sub 2@Se@sub 3@) grown on arsenic terminated silicon (Si) (100). Ga@sub 2@Se@sub 3@ crystallizes into a defected zinc-blende structure with every third of the Ga site vacant. Vacancies are necessary to maintain charge neutrality in the crystal, and are responsible for its highly anisotropic electrical and optical properties by ordering into line geometry. Scanning tunneling microscopy (STM) revealed that wire structure is two-unit-cell-wide with the separation between wires of about three-unit cell, and its direction is influenced by alternating symmetry of the initial substrate. We will discuss its atomic structure, evolution of its initial growth and the interface structure between Ga@sub 2@Se@sub 3@ and Si, based on our recent investigation using STM and core-level photoemission spectroscopy (PES). It is shown that the formation of the wire structure is strongly related to the ordering of structural vacancies, and we will present its growth model. This formation mechanism is unique to the prevalence of structural vacancies incorporated in Ga@sub 2@Se@sub 3@, unlike other nano-structure formation mechanisms driven by defects or strain, such as for InAs nanodots on GaAs or SiGe clusters on Si. This work is supported by NSF Grant DMR 0102427 and M. J. Murdock Charitable Trust. T. O. further acknowledges support from University Initiative Fund of the University of Washington, and D. A. S., UW-PNNL Joint Institute for Nanoscience research award.