Observation of Impurity-Driven Metal-Insulator Transitions in Quasi-1D Nanowires on a (Na, Li)-Added In/Si(111)-4 x 1 Surface

Abstract

We report that a small amount of foreign adsorbates, Na as well as Li, on a quasi-1 dimensional (1D) metallic In/Si(111)-4 x 1 surface induces a charge-density-wave (CDW)-type metal-insulator transition (MIT). From our intensity versus temperature curve of a characteristic low-energy electron diffraction spot we further find that the adsorbate-induced MIT is reversible upon crossing the transition temperature (T-c), which is found to be slightly higher than that of the clean surface. The behavior of the Fermi edge with temperature in our valence band photoemission spectrum for the Na(or Li)-added surface clearly reveals the insulating nature by the much reduced intensity when cooled below T-c. We discuss possible driving forces for the adsorbate-induced MIT.