Bias dependence of STM profiles around the quantum point contact

We report atomic-scale quantum point contacts (QPCs) formed parallel to the substrate surface. The QPCs are formed in domain boundary of a multidomain Bi{0 1 2} film on a Si(1 1 1)-β√3 × √3-Bi substrate, thus direct observation of the QPCs with a scanning tunneling microscope (STM) is possible. Bias dependence of STM images indicates that a localized electronic state exists near the Fermi level around the QPC. Presumably, the localized state originates from the electronic confinement in a cylindrical potential well along the conduction channel through the QPC.