Scanning work function microscopy

When a sample is locally excited with a highly focused raster-scanned beam of keV electrons, the variations DeltaPhi of the work function across the surface can be monitored from the shift of the onset energy for secondary electron emission along a fixed energy scale. The performance of that "onset" technique of work function microscopy and its incorporation into scanning Auger microprobes is described. The potentialities of this extremely surface sensitive technique for structural and chemical microanalysis are demonstrated by different experimental examples comprising work function analysis of surface reactions, and sputter depth profiling with in-situ Auger and work function spectroscopy. Scanning work function microscopy for surface microanalysis is shown to supply a lateral resolution down to the 10 nm range with a detection limit below 10(-2) of a monolayer.