Sub-monolayer coverages of Be grown on GaAs(001)-c(4 × 4) and (2 × 4)-β by molecular beam epitaxy studied by reflectance anisotropy spectroscopy and reflection high-energy electron diffraction

The techniques of reflectance anisotropy spectroscopy (RAS) also termed reflectance difference spectroscopy (RDS) and reflection high-energy electron diffraction (RHEED) have been employed to characterise the growth of submonolayer coverages (0.005 to 1.000 monolayer (ML)) of Be deposited onto the GaAs(001)-c(4 × 4) and (2 × 4)-β surfaces. The following series of surface reconstructions evolved with increasing Be coverages from 0 to 1 ML: GaAs(001)-c(4 × 4) → c(4 × 4)(1 × 2) → c(4 × 4)(1 × 3) → (1 × 2)(1 × 3) → (1 × 3) → (1 × 2); and, GaAs(001)-(2 × 4)-β → (2 × 4)(1 × 3) → (2 × 1)(1 × 3) → (1 × 2). The fact that unique, but highly reproducible, RAS signatures were obtained for each of these surface phases demonstrates the applicability of a combined RAS/RHEED system for monitoring sub-monolayer heteroepitaxial growth with a surface sensitivity of the order of 1100th of a monolayer.