Monohydride formation on vicinal Si(001) investigated by reflectance anisotropy spectroscopy

We report reflectance anisotropy spectroscopy (RAS) results for the controlled dosing of atomic hydrogen onto a clean 3 degrees offcut Si(001)-(1 x 2) sample, cut so as to expose a single domain under ultra-high vacuum (UHV) conditions. Upon dosing approximately 0.8 monolayers of atomic hydrogen onto this surface at room temperature, followed by annealing, large changes in the RAS lineshape are observed. These are attributed to terrace disorder, step roughening and to the formation of the monohydride Si(001)-(1 x 2)-H phase, respectively, with increased annealing temperature. However, a (1 x 2) LEED pattern is observed throughout H adsorption and after annealing. We compare the RAS spectrum for the monohydride phase with microscopic calculations of the optical response and interesting agreement is found in the region of 3.2 eV.