Collecting photoelectrons with a scanning tunneling microscope nanotip

The collection of photoelectrons excited with a synchrotron via a nanotip placed near the surface of a sample is studied. Simulating the electron trajectory, we found that photoelectrons escaping from the surface are too weak to be the only source of electrons contributing to a photocurrent detected with a scanning tunneling microscope tip, as reported recently. The tunneling of low-energy electrons generated with synchrotron irradiation is suggested as an additional channel contributing to the photocurrent at a small separation between tip and sample. An image based on x-ray absorption is expected to attain a resolution comparable to a topographical image. (C) 2008 American Institute of Physics.