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-sourc e molecular-beam epitaxy of Si on Si (001) surfaces have been used to establish a model for the dynamic changes in RA. The oscillatory behav ior of RA is firmly linked to the periodic variations in domain covera ge of the (2 x 1) + (1 x 2) reconstructed surface during growth under the monolayer by monolayer growth mode. The absence of changes in doma in coverage during growth interruption at 600 degrees C has also been demonstrated, which substantiates the prediction of Monte Carlo simula tions. By comparison of RA and RHEED response at high and low growth t emperatures, it has been shown that above 650 degrees C the absence of RA oscillations is linked to the change in growth mode from two-dimen sional nucleation to step flow, whereas their absence at temperatures below 550 degrees C is due to a change in the joint density of states caused by a change in the electronic configuration. The lack of oscill atory RA response during growth on misoriented surfaces is discussed i n terms of the averaging process in obtaining macroscopically observab le RA from anisotropic local polarizability.