Photoelectric evaluation of polarization and internal field in PZT thin films

Photoelectric phenomena were investigated in sol-gel derived lead zirconate -titanate (PZT) films. Two major illumination techniques were employed in o rder to assess both the ferroelectric polarization and internal field in th e films. Using semitransparent top electrodes and short UV pulses, the fast polarization-dependent photocurrent was observed and attributed to bulk ph otovoltaic effect. This current can be used for non-destructive readout of polarization state in non-volatile ferroelectric memories. In the other reg ime, opaque electrodes were employed and a steady-state current (or voltage in the open circuit conditions) was investigated caused by the illuminatio n of the area adjacent to the top electrode This polarization-independent c urrent was ascribed to the internal field due to oxygen-deficient layer nea r the film's surface. It is shown that the observed photocurrent is sensiti ve to the wavelength of the light and can be used for the evaluation of ele ctron band bending and electrical inhomegeneities across the film's thickne ss.