Chlorination of hydrogen-terminated silicon „111... surfaces

Infrared absorption spectroscopy was used to investigate the chlorination of hydrogen-terminated Si 111 surfaces by three different methods: a exposure to a saturated solution of phosphorus pentachloride PCl5 in chlorobenzene; b exposure to chlorine gas, Cl2 g , and c exposure to Cl2 g under UV illumination. X-ray photoelectron spectroscopy and first principles model clusters calculations were used to explore the structure and dynamics of these surfaces. The infrared spectra exhibited sharp chlorine-related vibrations at 586 and 527 cm−1. The narrow full width at half maximum of these vibrations for all three preparation methods indicated that all functionalization schemes produced a nearly complete monolayer of Cl with little surface roughening or introduction of step edges. The 527 cm−1 mode was at a much higher frequency than might be expected for the bending vibration of Si monochloride. Theoretical calculations show, however, that this vibration involves the displacement of the top Si atom parallel to the surface, subject to a relatively stiff potential, shifting its frequency to a value fairly close to that of the Si–Cl stretching mode on a Si 111 surface. © 2005 American Vacuum Society. DOI: 10.1116/1.1861941