Research Of The CaCu₃Ti₄O₁₂ Thin Films With Nonlinear Current-voltage Characteristic

CaCu₃Ti₄O₁₂（CCTO）has extraordinarily high dielectric constant and strong stability over a wide temperature range from 100 to 400 K, and also has remarkably nonlinear current-voltage characteristic. So CCTO is considered as a very promising material for application in microelectronics, especially in capacitive components and varistors.In this work, CCTO precursor solution was prepared by sol-gel method at room temperature, then the prepared CCTO solution was span on the Pt/Ti/SiO₂/Si substrate, After baking at 350 oC for 5 minutes on the heating plate,the samples were annealed in furnace finally. Varying the times of spin-coating and annealing temperatures, property and morphology of different samples were then characterized using X-ray diffractometer, field emission scanning electron microscope and semiconductor parameter analyzer in order to obtain the optimal condition for preparing the thin films.For the purpose of reducing the cost, and considering the compatibility with very large-scale integrated circuits, the experiments of preparing CCTO thin films on silicon substrate were also taken. Because oxygen atoms of CCTO would be captured by Si substrate in the annealing process, the CCTO can not crystallize. Therefore, ZnO layers were first deposited on Si substrate to obtain Si/ZnO/CCTO samples, then the microstructure and I-V property of composite films were determined.For the Pt/Ti/SiO₂/Si substrate, the thesis put forward two testing modes of I-V property. And the threshold voltages（VT） of each sample obtained by two modes exhibited nearly twofold relationship. Furthermore, the value of VT measured in the sample of CCTO/Pt was much lower than that of CCTO/ZnO/Si, which is related to the conducting path of current. And the experimental results can be interpreted by a simplified series varistor model. At last, a Double Schottky Barrier model was employed to explained the nonlinearity of CCTO thin films in detail. The testing results indicated that the CCTO thin films have outstanding nonlinear I-V property.