Thermionic transport across gold-graphene-WSe<sub>2</sub> van der Waals heterostructures.

Rosul, Md Golam; Lee, Doeon; Olson, David H; Liu, Naiming; Wang, Xiaoming; Hopkins, Patrick E; Lee, Kyusang; Zebarjadi, Mona · Sci Adv · 2019

basic_science · Level V

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Abstract

Solid-state thermionic devices based on van der Waals structures were proposed for nanoscale thermal to electrical energy conversion and integrated electronic cooling applications. We study thermionic cooling across gold-graphene-WSe<sub>2</sub>-graphene-gold structures computationally and experimentally. Graphene and WSe<sub>2</sub> layers were stacked, followed by deposition of gold contacts. The <i>I</i>-<i>V</i> curve of the structure suggests near-ohmic contact. A hybrid technique that combines thermoreflectance and cooling curve measurements is used to extract the device <i>ZT</i>. The measured Seebeck coefficient, thermal and electrical conductance, and <i>ZT</i> values at room temperatures are in agreement with the theoretical predictions using first-principles calculations combined with real-space Green's function formalism. This work lays the foundation for development of efficient thermionic devices.