The Role of Transport Agents in MoS2 Single Crystals

We report resistivity, thermoelectric power, and thermal conductivity of MoS2 single crystals prepared by the chemical vapor transport (CVT) method using I-2, Br-2, and TeCl4 as transport agents. The material presents low-lying donor and acceptor levels, which dominate the in-plane charge transport. Intercalates into the van der Waals gap strongly influence the interplane resistivity. Thermoelectric power displays the characteristics of strong electron-phonon interaction. A detailed theoretical model of thermal conductivity reveals the presence of a high number of defects in the MoS2 structure. We show that these defects are inherent to CVT growth method, coming mostly from the transport agent molecules inclusion as identified by total reflection X-ray fluorescence analysis (TXRF) and in-beam activation analysis (IBAA).