Preparation and electrical properties of 0.4Pb(Zn1/3Nb2/3)O-3-0.6Pb(Zr0.4Ti0.6)O-3 thin films by 2-step annealing method

Abstract

Films of (1-x)Pb(Zn1/3Nb2/3)O-3-xPb(Zr0.4Ti0.6) O-3 (x = 0.6, 40PZN-60PZT) were deposited on Pt/TiO2/ SiO2/Si substrate through spin coating. Using a combination of homogeneous precursor solution preparation and two-step pyrolysis process, we were able to obtain the 40PZN-60PZT thin films of perovskite phase virtually without pyrochlore phase precipitation after annealing above 650 degrees C. But since annealing done at the high temperatures for extended time can cause diffusion of Pt, TiO2 and Si, and precipitation of nonstoichiometric PbO, we adopted 2-step annealing method to circumvent these problems. The 2-step annealed films show dense microstructure than the 1-step films annealed at higher temperature. Furthermore, the root-mean-square surface roughness of 220 nm thick films which are annealed at 720 degrees C for 1 min and then annealed at 650 degrees C for 5 min was found to be 3.9 nm by atomic force microscopy as compared to the 12 nm surface roughness of the film annealed only at 720 degrees C for 5 min. The electrical properties of 2-step annealed films are virtually same and those of the 1-step annealed films annealed at high temperature. The film 2-step annealed at 720 degrees C for brief 1 min and with subsequent annealing at 650 degrees C for 5 min showed a saturated hysteresis loop at an applied voltage of 5 V with remanent polarization (P-r) and coercive voltage (V-c) of 25.3 mu C/cm(2) and 0.66 V respectively. The leakage current density was lower than 10(-5)A/cm(2) at an applied voltage of 5 V.