Adsorption of Ga on stepped Si(001) probed by resonant optical second harmonic generation

Abstract Resonant optical second harmonic generation (SHG) recently has been shown 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 structural 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 detected, and that contributions to the SH intensity from terraces and steps can be distinguished. In particular, it is shown that Ga atoms interact with the steps at room temperature, behaviour undetected by scanning tunnelling microscopy.