Surface sulfide on (100) W: formation, stability, absolute concentration of sulfur

Sulfur chemisorption on (100) W surface (grain-oriented ribbon) has been studied by AES with spectra measurements immediately under annealing of the sample up to T = 2000 K. A ‘surface sulfide’: sulfur cover forming under annealing of H2S adlayer and stable up to T = 1300 K have been found out. Using an original method, including an application of absolutely calibrated carbon atoms flux and an adsorption of CS2 molecules on the substrate under study, an absolute concentration of sulfur atoms in ‘surface sulfide’ have been determined. It appeared to be NS∗ = 1 × 1015 cm−2. Sulfur thermodesorption from (100) W surface has been studied and the dependence of bonding energy versus cover has been determined: E has been found to vary from 5.1 eV at θ = 0.2 till 4.4 eV at θ = 1.