VIBRATIONAL DYNAMICS OF THE IDEALLY H-TERMINATED SI(111) SURFACE

Picosecond sum-frequency generation measurements of the Si-H stretching vibration of an unreconstructed, ideally H-terminated Si(111) surface show that its lifetime is 0.8 +/- 0.1 ns. High resolution infrared reflection-absorption measurements reveal a marked temperature dependence of the linewidth, frequency and intensity of the Si-H stretching vibration. The width and frequency variations are completely accounted for by a weak coupling of this mode to a Si surface phonon centered at 210 +/- 25 cm-1. The loss in intensity, observed as the temperature is increased above 300 K, gives evidence for a strong coupling between the Si-H stretching and bending modes.