Step structure of silicon surface hydrogenated in solution as revealed with angle-resolved polarized infrared spectroscopy

Surface vibrations due to H atoms chemisorbed on a vicinal Si(lll) surface with [(1) over bar (1) over bar 2] steps were studied by angle-resolved polarized infrared spectroscopy. We observed stretching and wagging of the Si-H bonds and scissoring of the SiH2 structures, the last of which was missed in the previous investigation. To determine the direction of the dynamic polarization of each vibration, the surface electrical held made by the infrared beam was rotated in the ((1) over bar 10) plane. The step-edge structure was deduced by adopting the three-layer model. It was revealed that this step edge was formed by a strained vertical dihydride and a strained monohydride complex and that the dihydride was rotated to the [111] axis at 21 degrees from its bulk-terminated position resulting in a large angle of 65 degrees to the optical surface. This fully explains the discrepancy with the previous results regarding the electron energy loss and infrared spectra. (C) 1998 Elsevier Science B.V. All rights reserved.