THE CHARACTERIZATION OF THE GROWTH OF SUBMONOLAYER COVERAGES (1 200-TO-1 MONOLAYER) OF SI AND BE ON GAAS(001) - A REFLECTANCE ANISOTROPY SPECTROSCOPY AND REFLECTION HIGH-ENERGY ELECTRON-DIFFRACTION STUDY/

The techniques of reflectance anisotropy spectroscopy (RAS) and reflec tion high-energy electron diffraction (RHEED) have been employed, for the first time in concert, to characterize the growth of sub-monolayer coverages of both Si and Be deposited onto the GaAs(001)-c(4 X 4) sur face. The RHEED observations enabled the RAS spectra collected for a s eries of Si and Be coverages, in the range 0.005 to 1.000 monolayer (M L), to be interpreted in terms of changes in the sample surface struct ure. For the case of Si/GaAs(001) the following series of surface reco nstructions were observed with increasing Si coverage: c(4 X 4), c(4 X 4)/(1 X 2), (1 X 2), (1 X 2)/(3 X 1) and, (3 X 1). During the deposit ion of Be/GaAs(001), c(4 X 4), c(4 X 4)/(1 X 2), c(4 X 4)/(1 X 3), (1 X 2)/(1 X 3), (1 X 3), and (1 X 2) reconstructions were noted to evolv e. The fact that unique, but highly reproducible, RAS signatures were obtained for each of these surface phases demonstrates the applicabili ty of a combined RHEED/RAS system for monitoring sub-monolayer heteroe pitaxial growth with a surface sensitivity of the order of 1/200th of a monolayer.