[13p-1A-1~15] Trend of Functional Atomic Thin Film Application

[13p-1A-3] Thermoelectric properties of transition metal dichalcogenide monolayers

〇Kaito Kanahashi¹, Jiang Pu¹, Nguyen Thanh Cuoug², Lain-Jong Li³, Susumu Okada⁴, Hiromichi Ohta⁵, Taishi Takenobu^1,6 (1.Waseda Univ, 2.NIMS, 3.KAUST, 4.Tsukuba Univ., 5.Hokkaido Univ., 6.Waseda ZAIKEN)

Keywords:transition metal dichalcogenide,thermoelectric property

Monolayer transition metal dichalcogenides (TMDCs) have attracted a lot of research interests due to their two-dimensional layer structure. Recently, in single-crystal monolayer MoS₂, extremely high Seebeck coefficient (> 100 mV/K) was reported, suggesting high thermoelectric efficiency due to the low dimensional system. As a next step, it is necessary to investigate thermoelectric properties of other TMDC monolayers to search better thermoelectric materials. Particularly, for future applications, the large-area polycrystalline samples should be tested. Moreover, because Seebeck coefficient correlates with carrier density strongly, we should control the carrier density of samples to maximize Seebeck coefficient. Therefore, in this research, we clarify the carrier density dependence of Seebeck effect in CVD-grown large-area WSe₂, WS₂ and MoS₂ monolayers. For carrier-density control, we fabricated electric double layer transistors (EDLTs) using ion gel, which is the mixture of ionic liquid and organic polymer. Finally, we successfully accumulated hole and/or electron carriers (> 10¹³ cm^-2) and obtained relatively high Seebeck coefficient (~100 mV/K) for all in monolayer TMDC films.