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

Abstract 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, TiO x , 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 WSe x ( x < 2) as well as WO x . 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.