Using (secondary) photoelectron emission microscopy, we studied the fully formed 80 Angstrom Pt/n-GaP(001) interface with a lateral resolution better than 2 mu m. We probed the chemically etched and sulfur passivated GaP(001) surface by ultraviolet and soft x rays. The radiation source was either a deuterium lamp or the radiation from ELETTRA's U12.5 undulator. Due to their escape depth, the photoemitted secondary electrons carry chemical information of buried interfaces. The use of tunable synchrotron radiation enabled us to obtain chemical contrast by digital subtraction of the microimages taken at photon energies above and below each core-level absorption edge. The microimages revealed lateral changes in photoyield efficiency and chemical composition. The results were confirmed by x-ray photoemission spectromicroscopy measurements performed using A1 K alpha radiation. (C) 1996 American Institute of Physics.