A first-principles study of the SnO2 monolayer with hexagonal structure.

Abstract

We report the structural, electronic, magnetic, and elastic properties of a two-dimensional (2D) honeycomb stannic oxide (SnO2) monolayer based on comprehensive first-principles calculations. The free-standing and well-ordered 2D centered honeycomb SnO2 (T-SnO2) monolayer with D3d point-group symmetry has good dynamical stability, as well as thermal stability at 500 K. The T-SnO2 monolayer is a nonmagnetic wide-bandgap semiconductor with an indirect bandgap of 2.55/4.13 eV obtained by the generalized gradient approximation with the Perdew-Burke-Ernzerhof/Heyd-Scuseria-Ernzerhof hybrid functional, but it acquires a net magnetic moment upon creation of a Sn vacancy defect. The elastic constants obtained from the relaxed ion model show that the T-SnO2 monolayer is much softer than MoS2. The bandgap monotonically decreases with increasing strain from -8% to 15%. An indirect-to-direct bandgap transition occurs upon applying biaxial strain below -8%. Synthesis of the T-SnO2 monolayer is proposed. We identify the Zr(0001) surface as being suitable to grow and stabilize the T-SnO2 monolayer. The unique structure and electronic properties mean that the T-SnO2 monolayer has promising applications in nanoelectronics. We hope that the present study on the stable free-standing SnO2 monolayer will inspire researchers to further explore its importance both experimentally and theoretically.