Surface diffusion measurements from digitized FEM images: analysis of local brightness fluctuations

An extension of the field-emission current fluctuation method to study surface diffusion on the surface of a field emitter tip is proposed. The present approach is based on an analysis of the local brightness fluctuations extracted from digitized FEM video-images instead of the conventional probe-hole technique. “Virtual probe-holes” which correspond to probed surface regions of nanometer size can be placed in chosen areas of the image and the integrated intensity in these windows can be monitored with the time resolution of video frames (40 ms in our case). For the Li/Pt[1 0 0]tip system, the autocorrelation and crosscorrelation analyses of the local FEM brightness fluctuations have been performed. From a comparison of the experimentally obtained and theoretically calculated autocorrelation functions and from the crosscorrelation functions we determine the surface diffusion parameters for Li adatoms on the apex plane of the [1 0 0]-oriented Pt field emitter tip.