Field‐Dependent Electrical and Thermal Transport in Polycrystalline WSe2

WungYeon Kim; HyunJeong Kim; Toby Hallam; Niall McEvoy; Riley Gatensby; Hannah C. Nerl; Katie O'Neill; Rita Siris; Gyu‐Tae Kim; Georg S. Duesberg

Index: 10.1002/admi.201701161

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Abstract

Owing to their desirable electrical and thermoelectric properties, transition metal dichalcogenides (TMDs) have attracted significant attention. It is important to develop an easy synthetic method and a simple device fabrication process for TMDs. In this study, WSe2 films were synthesized on a large scale by thermally assisted conversion (TAC) of W films on SiO2/Si substrates at 600 °C. The TAC process yields homogeneous polycrystalline films of controlled thickness over large areas which have the advantage that they can be adapted for mass production for applications in electronics and thermoelectrics. In this regard, pre‐patterning of the deposited metal films allows for devices to be easily fabricated without any etch process. UV‐lithography‐defined W structures have been deposited and after conversion to WSe2 their electrical and thermoelectric properties have been studied. Using e‐beam lithography, a field effect transistor (FET) with a WSe2 channel was fabricated. This showed p‐type behavior and reasonable field effect mobility value. The thermoelectric properties of WSe2 thin films were analyzed by additionally integrating micro heating elements to the WSe2 FET. The maximum Seebeck coefficient and power factor (S2·σ) values were calculated to be ≈61 mV·K−1 (Vg = 45 V) and ≈1.3 nW·K−2·cm−1, respectively.