Dynamic changes in reflectance anisotropy from the Si(001) surface during gas-source molecular-beam epitaxy

Comparisons of simultaneous reflection anisotropy (RA) and reflection high-energy electron diffraction (RHEED) measurements during gas-source molecular-beam epitaxy of Si on Si (001) surfaces have been used to establish a model for the dynamic changes in RA. The oscillatory behavior of RA is firmly linked to the periodic variations in domain coverage of the (2×1) + (1×2) reconstructed surface during growth under the monolayer by monolayer growth mode. The absence of changes in domain coverage during growth interruption at 600°C has also been demonstrated, which substantiates the prediction of Monte Carlo simulations. By comparison of RA and RHEED response at high and low growth temperatures, it has been shown that above 650°C the absence of RA oscillations is linked to the change in growth mode from two-dimensional nucleation to step flow, whereas their absence at temperatures below 550 °C is due to a change in the joint density of states caused by a change in the electronic configuration. The lack of oscillatory RA response during growth on misoriented surfaces is discussed in terms of the averaging process in obtaining macroscopically observable RA from anisotropic local polarizability.