Atomic force microscopy of work functions on the nanometer scale

The Kelvin probe force microscope, introduced some years ago, has opened up several avenues of investigation. In this letter, we demonstrate that the technique is capable of distinguishing constituents of a metal alloy throug h their work-function differences. The intermetallics in the alloy are clea rly resolved. We discuss the basic principles of the measurement technique and present our results on aluminum/copper surfaces. The limits of the tech nique are also discussed. (C) 1999 American Institute of Physics. [S0003-69 51(99)04117-0].