The effect of submonolayer coverages of Ga on the optical anisotropy of vicinal Si(001)

The effect of submonolayer (ML) coverages of gallium on vicinal Si(001) has been investigated using reflectance anisotropy spectroscopy (RAS). A feature at 1.8 eV is sensitive to different annealing conditions and has been associated with optical transitions of the Si(001)(2 × 2)-Ga structure involving Ga dimers. The Si(001)(2 × 2)-Ga structure is stable to annealing to 600°C. The 1.8 eV feature is still evident after deposition of 1.5 ML Ga at room temperature, indicating that some Ga dimers from the (2 × 2)-Ga structure are still present at these coverages.