AVS 47th International Symposium
    Surface Science Thursday Sessions
       Session SS3-ThM

Paper SS3-ThM9
Reflectance Difference Spectroscopy of Mixed Arsenic-Rich Phases of Gallium Arsenide (001)

Thursday, October 5, 2000, 11:00 am, Room 210

Session: Surface and Interface Structure II
Presenter: D.C. Law, University of California, Los Angeles
Authors: D.C. Law, University of California, Los Angeles
M.J. Begarney, University of California, Los Angeles
L. Li, University of Wisconsin, Milwaukee
C.H. Li, University of California, Los Angeles
Q. Fu, University of California, Los Angeles
R.F. Hicks, University of California, Los Angeles
Correspondent: Click to Email
The relationship between the reflectance difference spectra and the atomic structure of arsenic-rich reconstructions of GaAs (001) has been investigated. Scanning tunneling micrographs reveal that a complex roughening process occurs as the surface structure changes with decreasing arsenic coverage from 1.75 to 0.75 monolayers (ML). With the loss of 0.1 ML of As, small pits, one bilayer in depth and having the same c(4x4) reconstruction as the top layer, form in the terraces. At the same time, gallium atoms are liberated to the surface, disrupting the c(4x4) ordering. With further arsenic loss, (2x4) domains nucleate and grow on top of the c(4x4). This underlying layer gradually decomposes into a metastable (2xn) phase, and finally into the (2x4). In the reflectance difference spectra, negative peaks at 2.25 and 2.8 eV correlate with the c(4x4)-like arsenic dimers. However, the intensity of the latter feature strongly depends on the presence of adsorbates, such as alkyl groups and gallium adatoms. A positive peak at 3.25 eV appears to be related to the (2xn) structure. Finally, the intensity of the positive peak at 2.9 eV is shown to be proportional to the density of (2x4)-type dimers.