AVS 46th International Symposium
    Surface Science Division Tuesday Sessions
       Session SS1+EM-TuM

Paper SS1+EM-TuM9
Photoelectron Diffraction of GaSe Bilayer Grown on Si(111)

Tuesday, October 26, 1999, 11:00 am, Room 606

Session: Nitrides and Compound Semiconductors
Presenter: S. Meng, University of Washington
Authors: S. Meng, University of Washington
B.R. Schroeder, University of Washington
A. Bostwick, University of Washington
E. Rotenberg, Lawrence Berkeley National Laboratory
F.S. Ohuchi, University of Washington
M.A. Olmstead, University of Washington
Correspondent: Click to Email
Initial nucleation of GaSe on Si(111)7x7 results in formation of a pseudomorphic bilayer, which passivates the substrate dangling bonds and serves as the interface for further film growth. Component-resolved photoelectron diffraction (PED) and low-energy electron diffraction show this bilayer is oriented in a single domain, with the Ga-Se bond aligned with the substrate Si-Si bond. Combining scanned-angle and scanned-energy PED with theoretical calculations reveals the Ga and Se atomic positions. Ga sits directly atop surface Si, and the resultant interface bonding leaves Se lone-pair states on the surface. This makes the Si(111):GaSe surface highly resistant to contamination, and even additional GaSe does not stick for T@sub substrate@@>=@550°C. The measured PED patterns of Ga and Se 3d states show strong forward focusing along Ga-Se bond as well as diffraction rings from in-plane Se-Se scattering. The Ga-Se bond angle is between that for layered GaSe and cubic Ga@sub 2@Se@sub 3@. PED also shows strong (>20%) angular variation of the Ga3d spin-orbit branching ratio, while the Se 3d branching ratio is constant within 5%. This is likely associated with differences in photoionization matrix element and propogation of 3/2 and 5/2 states for the different local environments. * Supported by NSF DMR9801302.