Second-harmonic generation from thick thermal oxides on Si(111): the influence of multiple reflections

Recently a number of second-harmonic-generation (SHG) experiments on (thick) oxide films on Si were performed as studies of the possible presence of strain, crystalline SiO2, a static electric field, and roughness at the Si–SiO2 interface. Large enhancements of the SHG anisotropy have been observed for thick oxide films. We show here that the SHG for thick thermal oxide films on Si(111) as a function of oxide thickness and angle of incidence is dominated by linear optics, owing to multiple reflections in the oxide film.