Electron localization and the nonmetal-to-metal transition at ultrathin alkali-metal/Si(111) interfaces

The K/Si(111)7 × 7 and K/Si(111)(√3 × √3)R30°-B interfaces are nonmetallic at room temperature saturation coverage. In contrast, the Cs/Si(111)7 × 7 interface metallizes below saturation coverage. Possible mechanisms of electron localization in pre-metallized films will be discussed. We conclude that electron correlation effects are important in determining the electronic properties of these interfaces.