Surface State Stark Shift in a Scanning Tunneling Microscope

Abstract

We report a quantitative low-temperature Scanning Tunneling Spectroscopy (STS)study on the Ag(111) surface state over an unprecedented range of currents (50 pA to 6 $\mu$A)through which we can tune the electric field in the tunnel junction of the microscope. We show that in STS a sizeable Stark effect causes a shift of the surface state binding energy $E_0$.Data taken are reproduced by a one-dimensional potential model calculation, and are found to yield a Stark-free energy $E_0$ in agreement with recent state-of-the-art Photoemission Spectroscopy measurements.

Accepted in Phys. Rev. Lett., 4 pages, 4 figures, revised version