Bulk and interface contributions to the optical second‐harmonic response of native‐oxide‐covered vicinal Si(111)

The optical second-harmonic response of native-oxide-covered vicinal Si(111), offcut by 3° towards [ 112], is compared with previous work at the same wavelength on similar samples, but offcut by 5° in the opposite, [112], direction. Sample rotation plots for sS, pS, sP and pP polarisation combinations are reported using 130 fs laser pulses of 765 nm wavelength, where mN indicates m-polarised input and N-polarised SH output. The two offcuts have different step geometries, but the same terrace structure at the Si/SiO 2 interface. In addition, the bulk quadrupolar contributions from the two offcuts are related by simple geometric factors. By using these constraints, simultaneous fitting of eight rotation plots allows the bulk and interface contributions to be estimated. These results offer the possibility of more detailed investigation of bond hyperpolarisability models, which have been applied recently to the vicinal Si/SiO 2 interface.