Photo‐Induced Enhancement in Ferroelectric Polarization and Abnormal Photo‐Conductivity in Polycrystalline Pt‐Sandwiched BiFeO3 Thin Film Capacitor

Polycrystalline BiFeO3 (BFO) thin film is directly deposited on Pt(111)/Ti/SiO2/Si(001) substrate at 550 °C by radio frequency (rf) magnetron sputtering. Metal Pt is used as top electrode to construct the symmetric Pt/BFO/Pt capacitor. The Pt/BFO/Pt capacitor exhibits photo‐induced enhancement in both remanent and switchable polarization when the capacitor is illuminated, which can be explained by the reorientation of ferroelectric polarization because of the trapping of photo‐induced carriers. The steady current density both in dark and in violet shows a diode‐like characteristic which is mainly dominated by the top Pt/BFO interface. In addition, an abnormal observation of the decrease regarding the illuminated current density with illumination time is acquired, indicating a difference from the conventional Si‐based p–n junction. The achieved results provide the evidence for the application of BFO‐based photo‐electric devices. Pt/BiFeO3/Pt capacitor exhibits photo‐induced enhancement in both remanent and switchable polarization when the capacitor is illuminated. The steady current density both in dark and in violet shows a diode‐like characteristic. An abnormal observation of the decrease regarding the illuminated current density with illumination time is acquired, indicating a difference from the conventional Si‐based p–n junction.