CaCu3Ti4O12 thin film capacitors: Evidence of the presence of a Schottky type barrier at the bottom electrode

This study aims to distinguish between the contributions of bottom and top electrodes to the dielectric properties of CaCu₃Ti₄O₁₂ (CCTO) based parallel plate thin film capacitors. For this purpose, Au, Pt, and La_0.9Sr_1.1NiO₄ as electrode materials were compared. Epitaxial and polycrystalline CCTO films were pulsed laser deposited. The nature of electrodes played a major role in altering the dielectric characteristics of the thin films. Existence of one or two Schottky barriers at either or both of the CCTO/electrode interfaces was observed. A careful comparison of the electrical characteristics allowed us to discriminate between the interfaces hosting the Schottky barrier without assuming the conduction type. In return, this knowledge of the Schottky barrier location allowed us to unambiguously establish the carrier's nature. Results point toward n-type carriers in CCTO thin films, in contradiction with previous reports.