Using (secondary) photoelectron emission microscopy, we studied the fu
lly formed 80 Angstrom Pt/n-GaP(001) interface with a lateral resoluti
on better than 2 mu m. We probed the chemically etched and sulfur pass
ivated 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 el
ectrons carry chemical information of buried interfaces. The use of tu
nable 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 la
teral changes in photoyield efficiency and chemical composition. The r
esults were confirmed by x-ray photoemission spectromicroscopy measure
ments performed using A1 K alpha radiation. (C) 1996 American Institut
e of Physics.