AVS 45th International Symposium
    Surface Science Division Monday Sessions
       Session SS1-MoM

Paper SS1-MoM8
Analysis of High-Index Si(001) Surfaces by Reflectance-Difference Spectroscopy

Monday, November 2, 1998, 10:40 am, Room 308

Session: Issues in Surface Electronic Structure
Presenter: L. Mantese, University of Texas, Austin
Authors: L. Mantese, University of Texas, Austin
Q. Xue, Tohoku University, Japan
D.E. Aspnes, North Carolina State University
Correspondent: Click to Email
High-index Si surfaces are of interest as potential substrates for electronic device applications. The growth properties of these surfaces are expected to be superior to those of the commonly used (001) and (111) orientations. It is believed that higher concentrations of surface steps may lead to higher nucleation densities. In addition, these surfaces provide new opportunities for meeting the requirements demanded by increasingly complex structures. Here, we consider the surface-induced optical anisotropies (SIOA) of three high-index Si surfaces: (113), (114) and (115) representing offcut angles of 25.2, 19.5, and 15.8 degrees from (001) toward [110], respectively. The SIOA of these surfaces were measured first in their air-oxidized conditions, second as-cleaned by heating, and third following Ge deposition. In some instances previous results on lower index Si(001) surfaces offcut 6 and 10 degrees toward [110] are available for comparison. The air-oxidized surfaces show sharp derivative-type structures near the critical point energies of bulk Si, consistent the lower index Si(001) surfaces. We have previously interpreted these structures in terms of photon-induced localization of the excited electronic states, which results from final-state correlation effects ordinarily discarded in conventional descriptions of optical absorption in solids. Spectra of clean reconstructed surfaces show a broad feature near 3 eV and a small step-related structure near the (E@sub 0@',E@sub 1@) transition of bulk Si. Atomic H exposure decreases the amplitude of the broad 3 eV feature suggesting it to be a dangling-bond-related state. In contrast, H exposure of Ge-deposited Si surfaces sharpens and enhances features below 3 eV while structures near the critical point energies of bulk Si remain. The optical response of Si(114) is consistent with its STM analysis, which indicates that this is the highest-index surface to demonstrate a terrace-plus-step morphology.