Gate Tunable MoS2-based Thermoelectric Devices

Two dimensional semiconductors and especially MoS2 have gained a lot of attention due to their unique properties. Finite bandgap, large Ion/Ioff ratio, good mobility, and nearly perfect subthreshold slope are among some of the features that make these materials attractive to researchers. While electrical transport has been studied extensively on single and multilayers of these Transition Metal Dichalcogenides (TMDs) [1,2], to the best of our knowledge, there has been no experimental study on their thermoelectric properties. Recently, it has been predicted that few layers of TMDs can provide extremely large power factor () and thus large ZT making them promising candidates as the future thermoelectric devices [3]. Here, for the first time, we explore gate-dependent thermoelectric properties of multilayer MoS2. As one of the important figures of merit for thermoelectric devices, we also calculate power factor which can then be used to find ZT. Multilayer MoS2 flakes ( ~ 8 nm) were prepared through standard scotch-tape exfoliation and then transferred onto the highly doped silicon substrate with 300 nm SiO2 layer on top (which can then be used as the back gate to tune the chemical potential inside the flake). E-beam lithography was then utilized to design the contact probes, heater, and also thermometers followed by deposition of Sc/Ni (30 nm/40 nm) as contacts (it has been previously demonstrated that Sc/Ni would provide ohmic contacts to MoS2 [4]). Fig. 1a shows room temperature transfer characteristic of the fabricated device where R1 and R2 are used as sourc