Ferroelectricity in solution-processed V-doped ZnO thin films

Abstract

A major hindrance in developing ferroelectric (FE) devices based on non-centrosymmetric and eco-friendly wurtzite ZnO is its non-switchable polarization. Doping with smaller ionic radii cations induces switchable polarization in ZnO; however, the remnant polarization achieved through doping is very low (2Pr < 2 μC/cm2), limiting its functionalities. Here we report V-doped ZnO thin films exhibiting 2Pr value as high as 12 μC/cm2 via a simple solution process. We achieved such a high polarization by controlling the crystallite size, morphology, and valence state of vanadium– which were optimized through variation of V-doping concentration and post-deposition annealing temperature. We found that the FE and dielectric properties of the V–ZnO films were directly linked to the crystalline size, morphology, and valence state of V. We also tested the applicability of V–ZnO as a coating layer on mesh type air filters and achieved a particulate matter filtering efficiency of up to 8%. Our study opens up the possibility of utilizing ferroelectric V–ZnO in particulate matter filtering devices.