Space charge effects in the photocurrent spectrum of ferroelectric Pb(Zr, Ti)O-3 thin films

Ferroelectric Pb(Zr-0.53, TiO0.47)O-3 (PZT) thin films were prepared on (11 1)Pt/Ti/SiO2/Si substrates by a sol-gel method. The ferroelectricity and ph otocurrent properties were investigated by using D-E hysteresis loops and p hotocurrent measurement (PCM) system. The band gap energy of PZT films, whi ch could be extrapolated from the-absorption coefficient spectrum, was abou t 3.6 eV. Typical photocurrent spectrums for the PZT him showed a large ano maly near 3.8 eV, that was connected with the band-to-band transition. In a ddition, two weak anomalies were also presented around 3.5 eV and 3.0 eV. T hey were related to space charge states such as Pb3+ and O- centers, respec tively. After switching 10(9) cycles, the peak energy of the photocurrent d ue to Pb3+ center was decreased in proportion to the remanent polarization.