VIBRATIONAL DYNAMICS OF THE SI-H STRETCHING MODES OF THE SI(100)/H-2X1 SURFACE

The lifetime T1 of the symmetric Si-H stretching mode for the Si(100)/H:2x1 surface is significantly longer (T1>6 ns at 100 K) than for Si(111)/H:1X1. T1 is strongly sample dependent and temperature dependent. Samples with the longest lifetimes also show the smallest inhomogeneous width. The difficulty in reproducing the longer lifetimes at low temperature indicates that the measured T1 may not be intrinsic and may by due to defects. The deuterated surface has a lifetime of 250±30 ps with little variation from sample to sample and a weak temperature dependence. It is expected to be the intrinsic lifetime. On the hydrogenated surface, the energy transfer time between the symmetric and asymmetric mode is measured to be 90±15 ps at 100 K. From photon-echo measurement, the measured dephasing time at 100 K is 75±5 ps. We propose that the dephasing on that surface is induced by a low-energy silicon phonon (200-300 cm-1) as for the Si(111)/H:1x1 surface. We derive an expression relating the dephasing time and the energy transfer time for the general case of two coupled oscillators and discuss its application to this system. © 1995 American Institute of Physics.