Ferroelectrical properties of W-doped lead zirconate titanate

Abstract

Effects of the dopant W on the ferroelectric properties of Pb(Zr0.3Ti0.7)O3 (PZT) have been studied. The PZT and PZT doped with W (PZTW) thin films were deposited on LaNiO3 bottom electrodes by pulsed laser deposition at an oxygen partial pressure of 300mTorr. X-ray diffraction of PZTW films revealed pure perovskite structure with increased (110) orientation, compared to that of PZT films with high (l00) orientation. Both secondary ion mass spectrometry and x-ray photoelectron spectra tests confirmed the existence of W ions in the PZTW films. Although the PZTW film showed decreased remnant polarization, the saturation polarization is increased and the coercive field was greatly lowered. Moreover, the PZTW film demonstrated an improved fatigue behavior than PZT film. The W dopants are believed to contribute to the improvement of the ferroelectric behavior of PZT thin films. Ab initio calculation indicated that the formation energy of the oxygen vacancies in PZT lattice under Pb-deficient conditions can be greatly increased by doping W, leading to a suppression of oxygen vacancy concentration. Furthermore, the W 5d states share the conduction band minimum with Ti 3d states, which helps reduce the occupation of Ti 3d states by the electrons released from oxygen vacancies. Therefore, the PZTW is less susceptible to fatigue.