Ambipolar Seebeck\nCoefficient in MoS<sub>2</sub>/MoS<sub>2</sub>–MoO<sub>2</sub> Graded Composites by Junction Reciprocation

We fabricated radially transformed growth of MoS<sub>2</sub> to\nMoS<sub>2</sub>–MoO<sub>2</sub> by the two-zone chemical vapor\ntransport (CVT) technique. The idea to apply heat, i.e., hot junction\n(<i>T</i><sub><i>H</i></sub>), on both the edges\nof the film has a distinct ambipolar Seebeck coefficient (<i>S</i>) of −20 μVK<sup>–1</sup> with MoS<sub>2</sub> as hot junction, and 69.5 μVK<sup>–1</sup> with\nMoS<sub>2</sub>–MoO<sub>2</sub> as hot junction. The positive <i>S</i> at MoS<sub>2</sub>–MoO<sub>2</sub> indicates fast\nhole injection at a lower degree of interface Fermi-level pinning\nand large asymmetry at the junctions through low energy carrier scattering\nin the multiple potential barriers at the interfaces of each region.\nThe decreased Θ<sub><i>D</i></sub> around 5 K than\nMoS<sub>2</sub> reveals the lattice softening due to reduced strength\nof chemical bonding at MoS<sub>2</sub>–MoO<sub>2</sub>. The\nreport propounds the potential utilization of multiple potential barriers\nfor thin film graded composites in thermoelectric applications.