Preferentially oriented Fe-doped CaCu3Ti4O12 films with high dielectric constant and low dielectric loss deposited on LaAlO3 and NdGaO3 substrates

Abstract

The colossal dielectric constant of calcium copper titanate (CCTO) thin films is generally accompanied by high dielectric losses which limit its potential for electronic miniaturization. Strategies for reducing the dielectric loss while keeping large dielectric constants are needed for various electrical applications of CCTO. This work aims to reduce the loss by means of doping preferentially oriented CCTO films with Fe3+ ions. Highly oriented undoped and Fe-doped calcium copper titanate (Fe-doped CCTO) thin films were fabricated by synthesizing CCTO on LaAlO3(100) and NdGaO3(100) substrates via a sol-gel spin casting method. The films with different Fe-doping concentrations (0, 1.6 and 2.6 wt%) were structurally and chemically characterized via energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. X-Ray Diffraction (XRD) patterns confirmed that our doped CCTO films had a cubic perovskite structure with well-defined preferential orientations of (h00) and (hh0) on LAO and NGO substrates, respectively. Preferentially oriented films having room temperature dielectric constants on the order of 1000 in conjunction with values of loss tangent smaller than 0.012 in the frequency range of 50 Hz-2 MHz were achieved. Temperature dependence of the dielectric constant and loss tangent revealed that Fe-doping decreased the dielectric loss via the lowering of the electrical conduction through CCTO grains.