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 f luctuations extracted from digitized FEM video-images instead of the c onventional probe-hole technique. ''Virtual probe-holes'' which corres pond to probed surface regions of nanometer size can be placed in chos en areas of the image and the integrated intensity in these windows ca n 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 cross correlation analyses of the local FEM brightness fluctuations have bee n performed. From a comparison of the experimentally obtained and theo retically calculated autocorrelation functions and from the crosscorre lation functions we determine the surface diffusion parameters for Li adatoms on the apex plane of the [1 0 0]-oriented Pt field emitter tip . (C) 1998 Elsevier Science B.V. All rights reserved.