Photoferroelectric Effects of Undoped and Extrinsic Ion-Doped PZT Thin Films

ABSTRACTDeposition by aqueous acetate solution (DAAS) technique was used to synthesize undoped and 5 wt% Cr-, Mn-, Eu-, or Pr-doped Pb(Zr0.53Ti0.47O3 [PZT] thin films. The dopant was incorporated into PZT either in the precursor coating solution or via thermal diffusion into undoped PZT. X-ray diffraction shows that ion-doped PZT thin films on Pt<l 1 l>/Ti/SiO2/Si<100> (in particular, the Mn- and Eu- doped samples) display better crystallinity and smaller lattice parameters than those on sapphire substrates. The enhancement of photoconductivity at visible wavelengths measured by excitation photocurrent spectroscopy (EPS) goes as Cr-doped∼Mn-doped > Eu-doped ∼ Pr-doped. Only Mn-doped PZT perovskites have the band gap energy red-shifted to 360 nm from 330 nm. The space charge (or photovoltaic) field was estimated to be < 8 v when about 100 v was applied to ion-doped PZT thin films with 260 or 320 nm light. By using laser irradiation at selected wavelengths and switching the polarity of applied bias voltage, the expected changes in resistance (Ry) and remanent polarization (±Pr) states were observed in the P-E hysteresis loops. The possible applications of extrinsic ion-doped PZT thin films in optical memory devices are discussed.