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 (SnO) monolayer based on comprehensive first-principles calculations. The free-standing and well-ordered 2D centered honeycomb SnO (T-SnO) monolayer with D point-group symmetry has good dynamical stability, as well as thermal stability at 500 K. The T-SnO 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-SnO monolayer is much softer than MoS. 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-SnO monolayer is proposed. We identify the Zr(0001) surface as being suitable to grow and stabilize the T-SnO monolayer. The unique structure and electronic properties mean that the T-SnO monolayer has promising applications in nanoelectronics. We hope that the present study on the stable free-standing SnO monolayer will inspire researchers to further explore its importance both experimentally and theoretically.

Optical absorption in monolayer SnO2

“…Using a 32/33% of the Hartree-Fock mixing parameter as suggested by Ref. [30] for the hybrid calculations, we obtain an indirect (direct) bandgap of 4.34/4.42 (4.87/4.95 eV) in agreement with the data of Xiao et al [28]. It is well-known that the bandgap systematically increases as the mixing parameter is increased [31] due to the increase in the Hartree-Fock exchange contribution to the exchange-correlation energy.…”

“…The direct quasiparticle bandgap is 6.92, 6.50, 4.41, and 2.91 eV for sqGW, G 0 W 0 , HSE06, and PBE calculations, respectively. The PBE bandgap is consistent with previous ones from semilocal functionals [28,29]. The sqGW direct (indirect) quasiparticle bandgap is large than the G 0 W 0 counterpart by 420 (340 meV).…”

“…It is well-known that the bandgap systematically increases as the mixing parameter is increased [31] due to the increase in the Hartree-Fock exchange contribution to the exchange-correlation energy. We observe that the 6.19 eV quasiparticle bandgap obtained from our G 0 W 0 calculation is ∼ 0.26 eV larger than the results of Xiao et al [28]. There are several potential sources for such difference not limited to the energy cutoff, potential, basis set, Brillouin zone sampling, and most importantly, the choice of a prior self-consistent data used as the starting point in the G 0 W 0 calculation.…”

“…There are several potential sources for such difference not limited to the energy cutoff, potential, basis set, Brillouin zone sampling, and most importantly, the choice of a prior self-consistent data used as the starting point in the G 0 W 0 calculation. For example, the data of Xiao et al [28] seem not to have accounted for the Sn-d states in their basis set. As explained below, there is a strong antibonding Sn-d-O-p interactions especially around the valence band maximum (VBM).…”

Strong phonon anharmonicity and low thermal conductivity of monolayer tin oxides driven by lone-pair electrons

“…A T-phase structure was predicted as the ground-state structure of monolayer SnO 2 . 25 The magnetic properties of Co-doped and transition metal doped monolayer SnO 2 have been investigated. 26,27 Compared to the intense research on the synthesis and electronic properties of 2D tin oxides, their thermal properties receive less attention.…”