Atomically-resolved, local surface photovoltage imaging through scanning tunneling microscopy (STM) was used to determine the energy, occupancy, and precise location of surface states created by single alkali metal adatoms and single missing atom defects on GaAs(110) and Si(100)2x1 surfaces. We took advantage of the fact that the electric field produced by the STM tip penetrates the surface except where there is a local Fermi-level pinning: It turns out that a single two-electron surface state can screen the tip-induced electric field very efficiently and pin the Fermi level within a sub-nanometer radius.
D. Gorelik, S. Aloni, & G. Haase, Surf. Sci. 432, pages 265-278 (1999). Local Fermi level pinning at a single adatom (Cs) or vacancy (As) on a GaAs(110) surface
S. Aloni, I. Nevo & G. Haase, Phys. Rev. B. 60, pages 2165-2168 (1999). Single Cs adatoms at Si(001)2x1 surfaces: A local surface photovoltage imaging study.
Dept. of Chemical Physics, The Weizmann Institute of Science
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