Giant Thermomechanical Bandgap Modulation in Quasi-2D Tellurium

Date

2024-01-01

Author

Hussain, Naveed
Ahmed, Shehzad
Tepe, Hüseyin U.
Ullah, Kaleem
Shehzad, Khurram
Wu, Hui
Shcherbakov, Maxim R.

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Lattice deformation via substrate-driven mechanical straining of 2D materials can profoundly modulate their bandgap by altering the electronic band structure. However, such bandgap modulation is typically short-lived and weak due to substrate slippage, which restores lattice symmetry and limits strain transfer. Here, it is shown that a non-volatile thermomechanical strain induced during hot-press synthesis results in giant modulation of the inherent bandgap in quasi-2D tellurium nanoflakes (TeNFs). By leveraging the thermal expansion coefficient (TEC) mismatch and maintaining a pressure-enforced non-slip condition between TeNFs and the substrate, a non-volatile and anisotropic compressive strain is attained with ε = −4.01% along zigzag lattice orientation and average biaxial strain of −3.46%. This results in a massive permanent bandgap modulation of 2.3 eV at a rate S (ΔEg) of up to 815 meV/% (TeNF/ITO), exceeding the highest reported values by 200%. Furthermore, TeNFs display long-term strain retention and exhibit robust band-to-band blue photoemission featuring an intrinsic quantum efficiency of 80%. The results show that non-volatile thermomechanical straining is an efficient substrate-based bandgap modulation technique scalable to other 2D semiconductors and van der Waals materials for on-demand nano-optoelectronic properties.

Subject Keywords

bandgap, engineering, hot pressing, non-volatile strain, optoelectronics, tellurium

URI

https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85198425098&origin=inward
https://hdl.handle.net/11511/110233

Collections

Department of Physics, Article