Strain effect on band structure and surface reactivity of ZnO monolayer

Using first-principles calculations, we systemically investigate the strain effect on band structure and surface reactivity of ZnO monolayer (ML). The change of lattice size with the strain affects the charge distribution from O atoms to Zn atoms. The bandgap of ZnO ML changes nonlinearly under the uniaxial strain and linear continuously under the biaxial strain. After adsorbing CO, the ZnO ML roughly maintains the planar structure with the tensile strain while becomes corrugated with the compressive strain. The interaction between the active Zn and the C atom results in charge transmission from the Zn to the O atom and the fluctuation of the ZnO ML. ZnO ML has the most surface adsorption of CO under a biaxial compressive strain, armchair direction the second and zigzag the third. The inequivalence of the strain directions can be explained by the effective mass of the atoms. The surface adsorption and catalytic activity of CO enhance with the increasing strain applied on the ZnO ML. These findings are expected to play a guiding role in the future design of ZnO-based 2D nano-electronics. Graphical abstract PDOS of active Zn centers in ZnO ML with biaxial strains. The strains are marked on the right side. The black dashed line marks the Fermi level. The red dashed arrows mark the trend of the DOS