Measurements of absolute bandgap deformation-potentials of optically-bright bilayer WSe$_2$

Indrajeet Dhananjay Prasad; Sumitra Shit; Yunus Waheed; Jithin Thoppil Surendran; Kenji Watanabe; Takashi Taniguchi; Santosh Kumar

doi:10.1063/5.0321694

paper

Measurements of absolute bandgap deformation-potentials of optically-bright bilayer WSe $_{2}$

arXiv:2412.00453 · doi:10.1063/5.0321694

Abstract

Bilayers of transition-metal dichalcogenides show many exciting features, including long-lived interlayer excitons and wide bandgap tunability using strain. Not many investigations on experimental determinations of deformation potentials relating changes in optoelectronic properties of bilayer WSe $_{2}$ with the strain are present in the literature. Our experimental study focuses on three widely investigated high-symmetry points, K $_{c}$ , K $_{v}$ , and Q $_{c}$ , where subscript c (v) refers to the conduction (valence) band, in the Brillouin zone of bilayer WSe $_{2}$ . Using local biaxial strains produced by nanoparticle stressors, a theoretical model, and by performing the spatially- and spectrally-resolved photoluminescence measurements, we determine absolute deformation potential of -5.10 $\pm$ 0.24 eV for Q $_{c}$ -K $_{v}$ indirect bandgap and -8.50 $\pm$ 0.92 eV for K $_{c}$ -K $_{v}$ direct bandgap of bilayer WSe $_{2}$ . We also show that $\approx$ 0.9% biaxial tensile strain is required to convert an indirect bandgap bilayer WSe $_{2}$ into a direct bandgap semiconductor. Moreover, we also show that a relatively small amount of localized strain $\approx$ 0.4% is required to make a bilayer WSe $_{2}$ as optically bright as an unstrained monolayer WSe $_{2}$ . The bandgap deformation potentials measured here will drive advances in flexible electronics, sensors, and optoelectronic- and quantum photonic- devices through precise strain engineering.

Measurements of absolute bandgap deformation-potentials of optically-bright bilayer WSe2​

Abstract

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Measurements of absolute bandgap deformation-potentials of optically-bright bilayer WSe $_{2}$