Dielectric and leakage current properties of sol–gel derived calcium copper titanate (CCTO) thin films and CCTO/ZrO2 multilayers

Dielectric properties and I–V characteristics of sol–gel prepared calcium copper titanate (CCTO) thin films and CCTO/ZrO2 multilayers on Pt/Ti/SiO2/Si substrates are investigated. The CCTO thin films show temperature and frequency independent dielectric constant near room temperature, characteristic of bulk CCTO; however the room temperature dielectric constant of the thin films is much lower (∼1200 at 100 kHz) than bulk CCTO (∼104). In the CCTO/ZrO2 multilayers, the dielectric constant is further reduced but the dielectric loss and leakage current are also much lower; moreover in the multilayers the dielectric constant remains frequency independent over a larger temperature range near the room temperature. An activated relaxation process is present in the temperature range 100–250 K with an activation energy of about 0.14 eV in all the films. The probable conduction mechanisms have been suggested on the basis of leakage current data. Various observations lead to the conclusion that the ZrO2 layers act as a very effective barrier for the diffusion of oxygen in the multilayers.