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Preparation of Liquid-exfoliated Transition Metal Dichalcogenide Nanosheets with Controlled Size and Thickness: A State of the Art Protocol
Published on: December 20, 2016
Bandgap Tunability of Transition Metal Dichalcogenide Atomic Layers
Quinton Rice1, Bagher Tabibi1, Felix Jaetae Seo1
1Advanced Center for Laser Science and Spectroscopy, Hampton University, Hampton, Virginia, 23668, USA.
Abstract:
The temperature-dependent bandgap of transition metal dichalcogenides (TMDCs, MX2; M = Mo or W; X = S, Se, or Te) is analyzed using the O'Donnell and Chen relation with parameters including the average acoustic phonon energy (〈ħω〉) and the electron-phonon coupling strength (s). Wider (narrower) tunability of the bandgap results from the larger (smaller) electron-phonon coupling strength for a constant acoustic phonon energy. A 1.5 eV bandgap change was observed for weak electron-phonon coupling (s = 2) as well as with the strong electron-phonon coupling (s = 30). However, the weak electron-phonon coupling leads to a linear decrease in the bandgap energy as a function of temperature above ~85 K while the strong coupling exhibits similar behavior after ~60 K. Narrower (wider) tunability of the bandgap results from the larger (smaller) acoustic phonon energy for a constant electron-phonon coupling strength. The slope of negative entropy of exciton formation is large (small) at lower (higher) temperature. The management of the electron-phonon interaction as well as the average acoustic phonon energy indicates the ability to control the bandgap.
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