Simultaneous current-, force-, and work-function measurement with atomic resolution

The local work function of a surface determines the spatial decay of the charge density at the Fermi level normal to the surface. Here, we present a method that enables simultaneous measurements of local work-function and tip-sample forces. A combined dynamic scanning tunneling microscope and atomic force microscope is used to measure the tunneling current between an oscillating tip and the sample in real time as a function of the cantilever's deflection. Atomically resolved work-function measurements on a silicon (111)-(7 x 7) surface are presented and related to concurrently recorded tunneling current and force measurements. (C) 2005 American Institute of Physics.