Polarized angle-resolved Raman spectra of the Si-H stretching vibrations on stepped H-terminated Si(111) surfaces confirm the constrained orientation of the step dihydride derived from ab initio cluster calculations. They further show that the step normal modes involve little concerted motion of the step atoms, indicating that step relaxation reduces the steric interaction much further than predicted.

• Received 2 August 1993

DOI:https://doi.org/10.1103/PhysRevLett.71.2280