Reducing dielectric loss in CaCu3Ti4O12 thin films by high-pressure oxygen annealing

Abstract

The nature of dielectric loss in high dielectric constant CaCu₃Ti₄O₁₂ (CCTO) thin films was systematically studied by characterizing the films grown in high-pressure oxygen annealing processes. The films were grown on (001) LaAlO₃ substrates by a polymer assisted deposition (PAD) technique while the annealing processes were performed in various high oxygen pressure environments. Microstructural characterizations by X-ray diffraction and atomic force microscopy indicated that the phase and morphologies of the films were strongly impacted by the annealing oxygen pressures. It was found that the high oxygen pressure annealing can significantly reduce the dielectric loss, which may be attributed to the TiO₂ phase separation in CCTO, good quality of thin films grown by the PAD technique and fewer oxygen vacancies. The optimized room temperature low dielectric loss tangent of 0.002 at 10–100 kHz was achieved in the samples annealed with high pressure O₂ of about 5 atm, which is more than one order of magnitude lower than that from the normal pressure annealed samples.