EVIDENCE OF METALLIC NATURE OF THE SURFACE BANDS OF AU/SI(557)

Abstract

We have studied temperature dependence of the two proximal bands, S1 and S2, from the one-dimensional (1D) Au/Si(557) system using angle-resolved photoemission spectroscopy with synchrotron photons. The intriguing feature of these bands reported earlier, metallic S1 and insulating S2 at room temperature [J. R. Ahn, H. W. Yeom, H. S. Yoon, and I. W. Lyo, Phys. Rev. Lett. 91, 196403 (2003)], has neither been reproduced nor understood properly yet. Our band images, however, unambiguously reveal that both bands behave nearly identically with temperature and remain metallic for 83 K <= T <= 300 K as seen by the well-defined Fermi-Dirac edges. We thus exclude the presence of a Peierls-type metal-insulator transition claimed earlier and discuss possible causes for the difference. The metallic nature of these bands is further illustrated by the presence of a satellite peak in the Au 4f(7/2) core level reflecting the 1D plasmon excitation.