Phase Transition Shift in Lead-Excess PZT Films Under UV Illumination

Abstract

Self-polarized PZT are ferroelectrics with a preferred polarization orientation at room temperature and becomes a paraelectric at high temperatures of about 460 • C. The ferroelectric-paraelectric phase transition temperature depends on stoichiometry of the PZT material and therefore on preparation technology. In this work, we present an ellipsometric study of lead excess Pb 1+x Zr 0.235 Ti 0.765 O 3 (PZT) films exhibiting a strong self-polarization in the temperature range of 20 to 500 • C under UV illumination. We obtained a shift of the ferroelectric-paraelectric phase transition temperature to lower values and an increase of the optical gap E 03 . The temperature dependences of the optical gap E 03 , the refractive index and the absorption coefficient at fixed wavelengths were determined.

UV-INDUCED CHANGES OF THE POLARIZATION PROFILE OF Pb(Zr,Ti)O3 THIN FILMS

“…By using a proper combination of photoactive light illumination and external electric field energetically unstable domain configurations were created, for instance head-to-head and tail-to-tail configurations [1,7]. As far as both domain configuration and internal electric fields affect the ferroelectric-paraelectric phase transition [8], a shift of the ferroelectricparaelectric phase transition temperature to lower values and an increase of the optical gap E 03 (obtained from isoabsorption curves at an absorption coefficient of α = 1000 cm −1 ) was detected under UV illumination in self-polarized PZT thin films [9]. After the UV lamp was switched off, all parameters including optical gap and the temperature of the phase transitions relaxed back to their initial values.…”