Ultrathin tellurium dioxide: emerging direct bandgap semiconductor with high-mobility transport anisotropy

Abstract

An effectively large bandgap and a high carrier mobility of two dimensional (2D) crystals are crucial in emerging materials for nanoelectronics. A previously unexplored two-dimensional material, monolayer TeO₂, is proposed to have high stability, a wide direct gap and high carrier mobility, based on first-principles calculations. Our results show that 2D TeO₂ is both thermally and dynamically stable. In addition, it is easily exfoliated from its bulk counterpart, a natural layered mineral tellurite. Importantly, 2D TeO₂ always exhibits a direct bandgap when thinning from bulk (3.32 eV) to monolayer (3.70 eV), an energy range not covered by previously reported 2D materials. Furthermore, monolayer TeO₂ is exceptional in high transport anisotropy, possessing not only high electron mobility (of the order of 1000 cm² V⁻¹ s⁻¹) but also exceptionally high hole mobility (up to 9100 cm² V⁻¹ s⁻¹). All these findings make 2D TeO₂ a promising candidate for both power electronics and short-wavelength optoelectronic applications.