Surface-Induced Enhancement of Piezoelectricity in ZnO Nanowires

Piezoelectric nanowires are promising building blocks in various micro-electromechanical systems. Using first-principles calculations, we systematically investigate the influence of surface and volume changes on piezoelectric coefficients in 001-oriented ZnO nanowires and hollow nanowires. We find that the increased non-axial ion displacements under strain near the 100 surface cause a notable enhancement in piezoelectric coefficients for these nanowires. Furthermore, by introducing the obtained surface modifications, we break through the limitation of simulation size and obtain the piezoelectric coefficients at the experimental size. Our findings are of importance to expand simulations and guide experimental explorations.