Surface vibrations in the T4 and H3 Pb phases on Si(111)

We present here a combined experimental Raman spectroscopy and ab initio theoretical study of the vibrational modes of the (√{3 }×√{3 } ) reconstructed SIC phase of Pb on Si(111) and discuss their relation to the atomic surface structure. The Raman response of the surface localized vibrational modes, in particular, is identified in the low-frequency spectral range (down to 15 cm^-1 ). We demonstrate that Raman spectroscopy is a very powerful approach to test atomic structures of surfaces and a valuable complement to standard surface analytics. While the calculated spectra of H3 and T4 are too similar to allow a discrimination of these phases, the good overall agreement to the measured Raman spectra enables a classification of the observed vibrational modes.