Effects of the local environment on Si-H stretching frequencies for the mixed coverage X/H:Si(111) surface (X = F, Cl, Br, and I)

The vibrational spectra of the Si(111)-(1 × 1) surface covered with a mixture of halides and hydrogen are explored using computational techniques with experimental validation. We have investigated the relationship between the Si-H stretching mode and halide coverage for fluorine, chlorine, bromine, and iodine. Our investigation shows that the blue shift of the v(Si-H) mode is approximately linear with respect to the halide coverage. Our predictions using density functional calculations are validated using experimental results on a ∼30% fluorinated surface. The origin of the shift is proposed to be an inductive effect along with lone pair donation from the halogen to the silicon surface. Our results indicate it is possible to use the v(Si-H) mode as a probe to measure halide coverage. Our results agree with earlier studies on analogous systems.