Preparation and electrical properties of 0.4Pb(Zn1/3Nb2/3)O3-0.6Pb(Zr0.4Ti0.6)O3 thin films by 2-step annealing method

Abstract

Films of (1−x)Pb(Zn 1/3 Nb 2/3 )O 3 -xPb(Zr 0.4 Ti 0.6 ) O 3 (x = 0.6, 40PZN-60PZT) were deposited on Pt/TiO 2 / SiO 2 /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 • C. But since annealing done at the high temperatures for extended time can cause diffusion of Pt, TiO 2 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 • C for 1 min and then annealed at 650 • 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 • 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 • C for brief 1 min and with subsequent annealing at 650 • 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 μC/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.