Second-harmonic generation at the interface between Si(100) and thin SiO2 layers

Abstract

In materials that have bulk inversion symmetry, optical second harmonic generation (SHG) is sensitive to regions where the inversion symmetry is broken, i.e., a surface or interface. We measure SHG from the interface between Si(100) and thin layers of SiO2. Measurements on a series vicinal samples (0°–5° off axis) show that one- and threefold symmetries in the SHG signal increase with increasing off-axis angle. Comparison to x-ray scattering measurements of the interface roughness, for a set of on-axis samples, demonstrates the sensitivity of SHG to interface roughness.