Structure and Dielectric Properties of Heteroepitaxial PMNT Thin Films

Abstract

Thin films of PbMg_1/3 Nb_2/3O₃(PMN) and (1 − x)PbMg_1/3Nb_2/3O₃-xPbTiO₃ (PMNT) with x = 0.1 to 0.3 were epitaxially grown on (100) MgO and (100) SrTiO₃ (ST) substrates by magnetron sputtering. Typical film thickness was 300 to 900 nm. Pyrochlore free (001) PMN and (001) PMNT thin films were grown on the ST and MgO substrates at narrow temperature window of 500 ± 20°C. The cross-sectional TEM image showed that the sputtered PMN and PMNT thin films comprised high density and continuous structure. These sputtered films showed 3-dimensional epitaxy. The dielectric response of the sputtered thin films showed frequency dispersion similar to bulk relaxor-like behavior with a broad temperature anomaly. PMN-23PT (x = 0.23) thin films showed the temperature of maximum, Tm, at 80°C. The Tm coincided with that of corresponding bulk materials. However, the obtained maximum dielectric permittivity, ϵ_m, ϵ_m = 900 to 1000, was considerably smaller than that in the bulk. The relatively low dielectric permittivity was probably due to the presence of strained hetero-epitaxial layer having temperature independent dielectric properties.

Keywords:

• PMN
• PMNT thin films
• strained hetero-epitaxial thin films
• relaxor