Temperature and thickness dependent permittivity of (Ba,Sr)TiO₃ thin films

The temperature and thickness dependence of permittivity of (Ba,Sr)TiO ₃ has been investigated. The films were deposited by liquid-source metalorganic chemical vapor deposition onto Pt/SiO₂/Si, with thicknesses ranging from 15 to 580 nm. The dielectric response was measured from 100 to 520 K. As film thickness decreased, the maximum dielectric constant decreased, the temperature at which the maximum dielectric constant occurred decreased, and the peak in the dielectric constant became more diffuse. A model incorporating a thickness independent interior and a nonferroelectric surface cannot account for these thickness dependencies. To appropriately model these observations a physical model containing thickness and temperature dependent interior and surface components is necessary.