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arXiv · 2302.06797

Giant Thermomechanical Bandgap Engineering in Quasi-two-dimensional Tellurium

Naveed Hussain·Shehzad Ahmed·Hüseyin U. Tep·Kaleem Ullah·Khurram Shahzad·Hui Wu·Maxim R. Shcherbakov
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Abstract

Mechanical straining-induced bandgap modulation in two-dimensional (2D) materials has been confined to volatile and narrow modulation due to substrate slippage and poor strain transfer. We report the thermomechanical modulation of the inherent bandgap in quasi-2D tellurium nanoflakes (TeNFs) via non-volatile strain induction during hot-press synthesis. We leveraged the coefficient of thermal expansion (CTE) mismatch between TeNFs and growth substrates by maintaining a high-pressure enforced non-slip condition during thermal relaxation (623 to 300K) to achieve the optimal biaxial compressive strain of -4.6 percent in TeNFs/sapphire. This resulted in an enormous bandgap modulation of 2.3 eV, at a rate of up to ~600 meV/%, which is two-fold larger than reported modulation rate. Strained TeNFs display robust band-to-band radiative excitonic blue photoemission with an intrinsic quantum efficiency (IQE) of c.a. 79.9%, making it promising for energy efficient blue LEDs and nanolasers. Computational studies reveal that biaxial compressive strain inhibits exciton-exciton annihilation by evading van-Hove singularities, hence promoting radiative-recombination. Bandgap modulation by such nonvolatile straining is scalable to other 2D semiconductors for on-demand nano(opto)-electronics.

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Naveed Hussain, Shehzad Ahmed, Hüseyin U. Tep, Kaleem Ullah, Khurram Shahzad, Hui Wu, Maxim R. Shcherbakov. 2023-02-14. Giant Thermomechanical Bandgap Engineering in Quasi-two-dimensional Tellurium. https://arxiv.org/abs/2302.06797

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