ADSORPTION OF CA ON STEPPED SI(001) PROBED BY RESONANT OPTICAL 2ND-HARMONIC GENERATION

Resonant optical second harmonic generation (SHG) recently has been sh own to be a powerful probe of Si surfaces and interfaces. In this work , a resonance in the region of 3.3 eV is exploited to reveal structura l information on the adsorption of Ga on vicinal Si(001) surfaces. It is shown that coverages of less than 0.01 monolayer of Ga can be detec ted, and that contributions to the SH intensity from terraces and step s can be distinguished. In particular, it is shown that Ga atoms inter act with the steps at room temperature, behaviour undetected by scanni ng tunnelling microscopy. (C) 1998 Elsevier Science S.A.