Work function microscopy as a tool for materials analysis

In this work, we describe the upgrading of a multitechnique surface analysis apparatus to perform work function microscopy. The onset method was used to measure de work function. A focused electron or ion beam may be used to produce secondary electrons. An external electronic circuit is used to compensate the sample potential and to detect the work function shift. This electronic unit has been specially built for this purpose. The AES (Auger Electron Spectroscopy) electron gun or the SIMS (Secondary Ion Mass Spectrometry) ion gun is used as primary beam. A hemispherical energy analyzer is used to select an energy window for the detected secondary electrons. Simultaneously with the work function image, a standard electron image can be acquired. A sample with 4 different metals was used to test this technique. The work function images showed a very good contrast allowing the identification of every metal. The results also let commenting on the state of cleanness of the surface.