About the preferential sputtering of chalcogen from transition metal dichalcogenide compounds and the determination of compound stoichiometry from XPS peak positions

We use the fact that for 2 keV Ar‡ ion bombardment the sputtering yield of the chalcogen X is higher than that of the transition metal M in transition metal dichalcogenide compounds MX2 (M ˆ W, Mo; X ˆ Te, Se, S) to obtain variations of stoichiometry in these materials. While the binding energy of the chalcogen is independent of the MXx stoichiometry (2 x 0:7), we ®nd a correlation between the stoichiometry decrease and the reduction of the M binding energy, which can be used to estimate the compound composition. For binding energies of BEM and BEX in a MXx compound we ®nd a linear dependence of (BEM ÿ BEX) on x. However, a simple correlation does not exist between the chemical shift of the metal and the electronegativity difference D(wX ÿ wM) between chalcogen and metal. # 2001 Elsevier Science B.V. All rights reserved.