Interface chemistry and thermoelectric characterization of Ti and TiOxcontacts to MBE-grown WSe2

WSe(2)has demonstrated potential for applications in thermoelectric energy conversion. Optimization of such devices requires control over interfacial thermal and electrical transport properties. Ti, TiOx, and Ti/TiO(x)contacts to the MBE-grown WSe(2)are characterized by XPS and transport measurements. The deposition of Ti is found to result in W-Se bond scission yielding metallic W and Ti-Se chemical states. The deposition of Ti on WSe(2)in the presence of a partial pressure of O-2, which yields a TiO(x)overlayer, results in the formation of substoichiometric WSex(x< 2) as well as WOx. The thermal boundary conductance at Ti/WSe(2)contacts is found to be reduced for greater WSe(2)film thickness or when Au/TiO(x)interface is present at the contact. Electrical resistance of Au/Ti contacts is found to be higher than that of Au/TiO(x)contacts with no significant difference in the Seebeck coefficient between the two types of contact structures. This report documents the first experimental study of Ti/WSe(2)interface chemistry and thermoelectric properties.