Tunable electronic structures of two-dimensional ZnO bilayers with different stacking

Two-dimensional ZnO materials have recently attracted widespread research attention for their promising properties, chemical stability, and mechanical strength. These special properties make them not only imply a scientific interest but also indicate great technological applications in optoelectronics, photonics, and sensors. Herein, based on the first-principles calculations with the HSE06 potential, the atomic structures and electronic properties of ZnO bilayer with different stacking are investigated. The results demonstrate that AB-stacking is the most energetically favorable configuration among all those considered. The AB-stacking is mechanically and dynamically stable. The calculated band gap is 2.88 eV using the HSE06 potential and 1.45 eV using the PBE potential. Moreover, we found that it is possible to modulate the energy bandgap both by the type of bilayer stacking and by the effect of the biaxial strain and interfacial distance. The ability to tune the energy bandgap in ZnO bilayers by adjusting their geometric configuration or applying an external strain or changing the interfacial distance could inspire new applications in various technological fields.