Study of the Ge(111)/GeO2 interface by optical second harmonic spectroscopy

The reflected optical second harmonic intensity from the Ge(111)/GeO2 interface has been measured in a dry nitrogen atmosphere as a function of the incident photon energy. The oxide layer was produced by thermally oxidizing a Ge(111) substrate in pure oxygen gas at 823 K. We have found that the SH intensity pattern as a function of the sample rotation angle around the surface normal changes drastically in the photon energy range near ℏω=1.17 eV in the p-polarized input and p-polarized output configuration. At this resonance, the anisotropic SH response from the interface has a dominant contribution to the SH intensity.