Ambipolar Seebeck Coefficient in MoS₂/MoS₂–MoO₂ Graded Composites by Junction Reciprocation

We fabricated radially transformed growth of MoS₂ to MoS₂-MoO₂ by the two-zone chemical vapor transport (CVT) technique. The idea to apply heat, i.e., hot junction (<i>T</i>_<i>H</i>), on both the edges of the film has a distinct ambipolar Seebeck coefficient (<i>S</i>) of -20 μVK^-1 with MoS₂ as hot junction, and 69.5 μVK^-1 with MoS₂-MoO₂ as hot junction. The positive <i>S</i> at MoS₂-MoO₂ indicates fast hole injection at a lower degree of interface Fermi-level pinning and large asymmetry at the junctions through low energy carrier scattering in the multiple potential barriers at the interfaces of each region. The decreased Θ_<i>D</i> around 5 K than MoS₂ reveals the lattice softening due to reduced strength of chemical bonding at MoS₂-MoO₂. The report propounds the potential utilization of multiple potential barriers for thin film graded composites in thermoelectric applications.