Condensed phase diagrams for the metal-W-S systems and their relevance for contacts to WS2

Motivated by interest in contacts to the layered semiconductor WS2, this study investigates condensed phase equilibria in M-W-S systems (M = transition or post-transition metal) and relates the findings to earlier work on M-Mo-W systems. Thermodynamic data were collected or estimated for the binary phases bearing M, W, and/or S; and a literature search for existing ternary phases was performed. Condensed phase M-W-S isothermal phase diagrams were calculated where sufficient data was available. These phase diagrams reflected three general forms. The early transition metals and group 13 post-transition metals were mostly reactive with WS2, with the resulting diagrams being either metal sulfide dominant or ternary/solid solution dominant. The late transition metals were all WS2 dominant, where the metal is in equilibrium with WS2. These findings are similar to those from our earlier study on the M-Mo-S phase diagrams and can be used to guide studies on contacts to WS2. (C) 2016 Elsevier B.V. All rights reserved.