Effects of temperature and Ti-nonstoichiometry on electric properties of CaCu₃Ti₄O₁₂ thin films

In this work the nonlinear current–voltage characteristics of CaCu₃Ti_4+xO_12+2x (X = 0, ±0.1, ±0.2, ±0.3) films prepared by sol–gel method are studied. X-ray diffraction results show that samples are all in good crystalline structures. Second phases existing in Ti non-stoichiometric CCTO films will have influence on the barrier height of interface and the breakdown voltage. Non-linear current–voltage properties are measured by a semiconductor parameter analyzer and show that the variation of Ti content in CCTO films will increase the breakdown voltages under room temperature. The temperature dependence of current–voltage curves and the relationship between voltage and current show the non-stoichiometric films are much sensitive to temperature variation. And the breakdown voltages of CCTO films decrease with the rising temperature. Considering Cu oxide layer may exist at the surface of film and segregates the semiconductor from metal electrode, the metal–insulator–semiconductor structure combined by Au/CCTO/Pt is used to explain the carrier transport mechanism of films under applied voltage. Thermionic emission may be the major factor for carrier transport at the beginning of applied voltage.