Nanoscale Probing of High Photovoltages at 109° Domain Walls

We report the direct observation of nanoscale photovoltaic current-voltage properties associated with directional steps of the electrostatic potential at 109° domain walls in ferroelectric BiFeO3 thin films with highly ordered ferroelectric stripe domains. The unidirectional photovoltaic effect along the net-in-plane polarization direction is shown to exhibit anomalies at the micro- and nanoscale due to local differences in mesoscopic domain structure. Very high initial photovoltages for small electrode spacings are observed using a conductive AFM tip as one of the electrodes in photovoltaic I-V measurements.