Microstructures and electrical properties of CaCu₃Ti ₄O₁₂ thin films on Pt/TiO₂/SiO₂/Si substrates by pulsed laser deposition

We investigated microstructures, compositional distributions, and electrical properties of dielectric CaCu₃Ti₄O₁₂ (CCTO) thin films deposited on Pt/TiO₂/SiO₂/Si substrates from 700 to 800 °C by pulsed laser deposition. With increasing the deposition temperature from 700 to 750 °C, the dielectric constants (ε_r) of CCTO films were greatly enhanced from ∼300 to ∼2000 at 10 kHz, respectively. However, the ε_r values of CCTO films were gradually decreased above 750 °C, which was surely attributable to the formation of a TiO₂-rich dead layer at the interface between CCTO and Pt electrode. Compositional analyses by Auger electron spectroscopy, energy dispersive spectroscopy, and electron energy loss spectroscopy revealed that the TiO₂-rich dead layer became thicker because of severe Cu diffusion from CCTO films to Pt electrode. The leakage current behaviors of CCTO films are in good agreement with Poole-Frenkel conduction mechanism, where both the TiO₂-rich dead layer and rutile TiO₂ nanocrystalline particles are considered to play a role of charge trapping centers.