AVS 46th International Symposium
    Surface Science Division Tuesday Sessions
       Session SS-TuP

Paper SS-TuP12
Vacancy Mediated Growth of Ga@sub 2@Se@sub 3@ Thin Films

Tuesday, October 26, 1999, 5:30 pm, Room 4C

Session: Poster Session
Presenter: Z. Qian, University of Washington
Authors: Z. Qian, University of Washington
Z. Dai, University of Washington
F.S. Ohuchi, University of Washington
K. Ueno, University of Tokyo, Japan
A. Koma, University of Tokyo, Japan
S. Meng, University of Washington
M.A. Olmstead, University of Washington
Correspondent: Click to Email
Ga@sub 2@Se@sub 3@ thin films were grown on GaAs(100) and Si(111) substrates by molecular beam epitaxy (MBE). In spite of large differences in lattice and symmetry found in GaAs(100) and Si(111), reflection high energy electron diffraction (RHEED) showed that the Ga@sub 2@Se@sub 3@ thin films were epitaxially grown on both surfaces. Electronic structures were determined by ultraviolet photoelectron spectroscopy (UPS) and electron energy loss spectroscopy (EELS). For the Ga@sub 2@Se@sub 3@ thin films growth on GaAs(100) substrate, transmission electron microscopy (TEM) revealed that vacancies were distributed on one set of the [111] crystal planes of @alpha@-Ga@sub 2@Se@sub 3@ structure by forming a @sr@3x@sr@3 configuration, resulting in the formation of vacancy ordered @beta@-Ga@sub 2@Se@sub 3@ structure. In this structure, modulation periodicity along [110] crystal directions was three times larger than that of @alpha@-Ga@sub 2@Se@sub 3@, and the crystal structure was consistent to the model proposed by Lübbers and Leute for bulk material (J. Solid State Chem., 43 (1982) 339). Very different nature of the growth habit was observed on the Si(111). High population of planer defects observed in the thin film was regarded as the result of Ga vacancy ordering in the crystal structure of Ga@sub 2@Se@sub 3@. We claim that the vacancies play an important role in determining the thin film structure in addition to lattice and symmetry matching conditions in the heteroepitaxy.