Clarification of Size Effects in Polycrystalline BaTiO₃Thin Films by Means of the Specific Heat Measurements: Grain Size or Film Thickness?

Abstract

Specific heat of polycrystalline BaTiO3 thin films on the fused quartz substrate was measured by ac-hot probe method. Phase transition temperature and excess entropy were determined as a function of film thicknesses and grain sizes. The variation of the latter was obtained in the limits 30–150 nm by changing of the temperature of the substrate during sputtering while thickness of films 20–1100 nm was controlled by the time of sputtering. It was found that the relation between the thickness and grain size is important for the size effects in polycrystalline films.