Microstructures and electric properties of highly (111)-oriented Nb-doped Pb(Zr_0.2,Ti_0.8)O₃ films with Pb _0.8La_0.1Ca_0.1Ti_0.975O₃ seed layer

A series of highly (111)-oriented tetragonal Nb-doped Pb(Zr _0.2Ti_0.8)O₃ (PNZT) films with Pb _0.8La_0.1Ca_0.1Ti0.975O₃ (PLCT) seed layers of variant thickness were deposited on the Pt(111)/Ti/SiO₂/Si substrates by sol-gel processing. It was found that the PLCT seed layer played a significant role on the microstructures and electrical properties of the PNZT films. The PNZT thin film with 5-nM-thick PLCT seed layer displayed enhanced electrical properties such as a large remnant polarization P_r (60 μC/cm²) and a low coercive field E_c (51 kV/cm) at room temperature. The enhancement of electrical properties can be attributed to the rough surface structures of the PLCT seed layer, which offered nucleation sites to reduce the crystallization activation energy of PNZT films and thus facilitated the polarization response. The PLCT seed layer also can act as a capacitive interface layer, reducing or compensating for the vacancy-type defects of PNZT film effectively, which results in the relatively low current density of PNZT film. These results indicate that the fabricated film is a good candidate for high-density memories application.