Strain-engineered electronic and thermoelectric properties of ZrX2 (X=S, Se) monolayers: A first-principles study

Abstract

Through comprehensive first-principles calculations coupled with Boltzmann transport theory, we systematically investigate the strain-dependent structural, mechanical, electronic, and thermoelectric properties of monolayer ZrX₂ (X = S, Se). Our mechanical analysis reveals both materials maintain exceptional stability under biaxial strains ranging from −10 % to +10 %, with ZrS₂ exhibiting superior mechanical robustness as evidenced by its higher Young's modulus (73.95 N/m) compared to ZrSe₂ (63.70 N/m). Detailed electronic structure calculations employing the TB-mBJ potential demonstrate these monolayers are indirect band gap semiconductors, with fundamental gaps of 1.8 eV for ZrS₂ and 1.16 eV for ZrSe₂. Notably, compressive strain induces dramatic electronic transitions, reducing the band gap progressively until ZrSe₂ undergoes a complete semiconductor-to-metal transition at −10 % strain. The thermoelectric transport properties show remarkable strain sensitivity. Applied biaxial strain enhances the power factor by an order of magnitude, reaching exceptional values of 2.4 × 10¹¹ W/mK²s for ZrSe₂ at −6 % strain. Comparative analysis reveals n-type doping consistently outperforms p-type configurations in thermoelectric efficiency across all strain conditions. These enhancements originate from strain-induced modifications to both electronic band structures and carrier scattering mechanisms. Our combined mechanical, electronic, and thermoelectric characterization provides fundamental insights into the strain-response of ZrX₂ monolayers, demonstrating their exceptional tunability for next-generation flexible electronics, strain sensors, and high-efficiency energy conversion devices. The comprehensive dataset presented here establishes a foundation for future experimental investigations and device applications of these promising 2D materials.