Deposition and Characterization of Ferroelectric Pb[(Mg1/3Nb2/3)xTi1-x]O3 Thin Films by RF Magnetron Sputtering

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Abstract
Ferroelectric Pb[(Mg1/3Nb2/3) x Ti1- x ]O3 (PMNT) thin films with a well-developed perovskite structure were prepared on Si(100) and Pt/Ti/ SiO2/Si(100) substrates by rf magnetron sputtering deposition at high substrate temperatures of 480–650° C. The effect of substrate materials was investigated by X-ray diffraction analysis. The substrates that were topped with a Pt/Ti electrode exhibited a significant effect on reducing the perovskite phase formation temperature of PMNT films; in addition, the TiO2 rutile phase was found to be formed at the interface between the PMNT film and Pt electrode. It was discovered that the TiO2 rutile phase would degrade the dielectric and ferroelectric properties of the PMNT films. The 0.5-µm-thick perovskite PMNT films of x=0.3–0.5 exhibited a high dielectric constant (k) of 1000–1300, and a dissipation factor less than 0.04 at 1 kHz. Moreover, the films showed satisfactory ferroelectric characteristics. The remanent polarization (P r) or coercive field (E c) ranged from 23.5 µ C/cm2 and 82.5 kV/cm, respectively, for 10 PMNT (x=0.1) to 10.2 µ C/cm2 and 49 kV/cm for 50 PMNT (x=0.5) thin films. Due to the formation of a relatively thick TiO2 interface layer at a high deposition temperature, the 70 PMNT (x=0.7) films did not show satisfactory dielectric or ferroelectric properties. However, by adding 3 mol% La on the PMNT to reduce the perovskite formation temperature, a 0.5-µm-thick Pb0.97La0.03Mg0.235Nb0.44Ti0.325O3 (PLMNT) film was prepared on the Pt/Ti/ SiO2/Si substrate, and results of P r=8.5 µ C/cm2, E c=46 kV/cm with k=1220 and tan δ<0.04 were obtained.