The structure and vibrational spectrum of the Si(111) - H/Cl surface

In this work, the vibrations of mixed coverage Si(111) - H/Cl surfaces are determined using quantum chemical calculations and Fourier transform infrared spectroscopy. The structure and symmetry considerations of the modes are used to assign the vibrational frequencies for varying coverages of both hydrogen and chlorine on the surface. Significant shifts in the Si - H and Si - Cl stretching frequencies are found as a function of coverage, while the bending modes are shifted very slightly. Our results suggest that Si - H stretching shifts can be used as a probe for chlorine coverage during the reaction of chlorine precursors with the hydrogen-terminated Si(111) surface. Finally, an analysis of coverage dependence suggests that a chemical inductive effect is the dominant origin of the resulting stretching frequency shifts, though a small contribution from the lone pairs interacting with the surface is also possible.