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

Abstract

Abstract WSe2 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/TiOx contacts to the MBE-grown WSe2 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 WSe2 in the presence of a partial pressure of O2, which yields a TiOx overlayer, results in the formation of substoichiometric WSex (x < 2) as well as WOx. The thermal boundary conductance at Ti/WSe2 contacts is found to be reduced for greater WSe2 film thickness or when Au/TiOx interface is present at the contact. Electrical resistance of Au/Ti contacts is found to be higher than that of Au/TiOx 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/WSe2 interface chemistry and thermoelectric properties.