Dynamic reflectance anisotropy and reflectance measurements of the deposition of Si on GaAs(001)-c(4X4)

Dynamic reflectance anisotropy and reflectance data recorded using a photon energy of 1.96 eV is presented for the deposition of atomic Si on singular GaAs(001)-c(4 x 4) surfaces under molecular beam epitaxy conditions at 400, 450 and 500 degrees C. Changes in reflectance anisotropy were detected at the 0.1% of a monolayer level underlining the sensitivity of the method. Dynamic changes were found in the reflectance anisotropy response upon the interruption of dosing providing a caveat that static reflectance difference spectroscopy does not provide true dynamical information on the surface processes and that temporal information on surface migration is available. Evidence for dramatic changes in reflectance was found during deposition, these changes being particularly pronounced at higher temperatures and are an indicator of surface roughening processes. Subsequent growth of GaAs returns the surface to GaAs like behaviour after similar to 15 monolayers and provides real time evidence for Si segregation at the surface.