XPS investigation of preferential sputtering of S from MoS and 2 determination of MoS stoichiometry from Mo and S peak x positions

The preferential sputtering of S from bulk MoS2 standard samples exposed to 3 keV Arq ion bombardment has been studied by XPS. The MoS stoichiometry decreases from MoS to MoS with a concomitant reduction in the Mo 3d x 2 1.12 5r2 binding energy from 229.25 to 228.35 eV. The altered layer extends to a depth of 3.8 nm and is proposed to consist of a single amorphous MoS phase in which Mo has a varying number of nearest neighbour S atoms. Using peak positions alone x it is possible to determine the MoS stoichiometry to an accuracy of x"0.1 from a plot of MoS stoichiometry against Mo x x 3d5r2–S 2p3r2 . binding energy. The results are of strong current interest for coating analysis applications as MoS2 is a compound capable of providing low friction properties when incorporated into hard coatings. q1999 Elsevier Science B.V. All rights reserved