Flexoelectric healing of intrinsically more conductive nanochannels in NdNiO3 thin films

Rare-earth nickelates have received great attention owing to the extreme sensitivity of their metal-insulator transition (MIT) and particularly the local defect state under external perturbation. Accordingly, it is critical to effectively control their local defect state to tailor the MIT. However, although macroscopic MIT behavior has been extensively studied, the relationship between the local defect state related to polar discontinuity and MIT has been rarely investigated. Herein, we demonstrate the presence of intrinsic conductive nanochannels due to the Ni deficiency induced by the polar discontinuity and the flexoelectric healing of such nanochannels in NdNiO3 thin films using atomic force microscopy (AFM). The results indicate that the intrinsic conductive nanochannels are likely related to the Ni vacancy. Intriguingly, these conductive nanochannels are effectively removed by the application of mechanical force with the AFM tip, i.e., flexoelectric healing. Our findings suggest that mechanical stimuli can be one of the effective ways for modulating the intrinsic defect state and the corresponding properties at the nanoscale.