Conductivity of the Si(111)7x7 dangling-bond state

Conductivity of the metallic dangling-bond state of adatoms on Si(111)7x7 clean surface was determined through passivation of the only electrical channel by similar to 0.1 monolayer Na adsorption. Through systematic measurements of electron transport and photoemission spectroscopy during the Na deposition, Si(111)7x7 was found to exhibit a metal-to-insulator transition. The decrease in conductivity through the transition, which is attributed to the conductivity of the dangling-bond state, was 2-4 mu Omega(-1) square(-1). The value is smaller than the two-dimensional Ioffe-Regel limit and the mean-free path is too short to apply the Boltzmann picture.