Step structure on HrSi formed in hot water as revealed with angle-resolved polarized infrared spectroscopy

Stretching, scissoring, and wagging due to H atoms chemisorbed on Si surfaces were observed on several vicinal 111. surfaces by infrared spectroscopy in nitrogen atmosphere while surface electric fields were controlled. By analyzing the response to the electrical field, orientation of the dynamic polarization, Pdyn, for each vibration mode was determined. These vibration modes were associated with specific bulk-terminated chemisorption sites for H atoms on these surfaces. The H-terminated vicinal 111.surfaces with 112:steps were characterized by H atoms forming monohydrides on the 111. terrace and monohydride chains at the 112:step-edges. The anisotropy of the Pdyns showed that these step edges were atomically straight along 110:and had the translational symmetry of Si crystal. On the surface with 112:steps, we detected scissoring of the SiH2 structures, which was missing in the previous investigation, as well as stretching and wagging of the Si–H bonds. By rotating the surface electrical field in the 110.plane we obtained angle-resolved absorption spectra. By analyzing the absorption features we determined the direction of the dynamic polarization of each vibration. The step-edge structure was deduced by adopting the three-layer model with an experimentally determined screening factor. 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 110:axis at 218 from its bulk-terminated position resulting in a large angle of 658 to the optical surface. q1998 Elsevier Science B.V. All rights reserved.