XPS STUDIES OF THE STABILITY OF A MIXED ZIRCONIUM-OXIDE AND SULFIDE THIN-FILM

A 25 Angstrom film formed by depositing zirconium (similar to 2 Angstr om min(-1)) onto gold foil in the presence of H2S (similar to 5 X 10(- 8) mbar) and H2O (similar to 1 X 10(-9) mbar) has been studied by XPS. This film has an outer region composed of a mixed zirconium oxide/sul phide, while below there is metallic zirconium plus Zr/Au alloy in con tact with gold. This film appears stable on heating to 400 degrees C u nder UHV insofar as the sulphide part does not change, although the ox ide part increases apparently as a result of some reaction of metallic zirconium with ambient water. By contrast, when this preheated film a t room temperature was treated with a hydrogen plasma, the sulphide co mponent was completely removed and the whole film was converted to the ZrO2-like form with enhanced formation of OH groups. The hydrogen pla sma treatment is therefore capable of desulphurising the mixed zirconi um oxide/sulphide film.