Phase change and electrical properties of thin films BaTiO/sub 3/ system made by RF/DC magnetron sputtering

Thin films of the BaTiO/sub 3/ system were prepared by radio frequency (RF)/DC magnetron sputtering method. We have investigated crystal structure, surface morphology and PTCR (positive-temperature coefficient of resistance) characteristics of the specimen depending on second heat-treatment temperatures. Second heat treatments of the specimen were performed in the temperature range of 400 to 1350/spl deg/C. X-ray diffraction patterns of BaTiO/sub 3/ thin films show that the specimen heat treated below 600/spl deg/C is an amorphous phase and the one heat treated above 1100/spl deg/C forms a crystal. In the specimen heat-treated at 1300/spl deg/C, the lattice constant ratio c/a is 1.188. A scanning electron microscope (SEM) image of BaTiO/sub 3/ thin films shows that the specimen heat treated in between 900 and 1100/spl deg/C shows grain growth. At 1100/spl deg/C, the specimen stops grain-growing and becomes a crystal. The resistivity-temperature characteristic of the specimen depends on the doping concentrations of Mn. A resistivity ratio between the value at room temperature and the one above Curie temperature is 10/sup 4/ for pure BaTiO/sub 3/ thin films and 10/sup 5/ for BaTiO/sub 3/:0.127 mol% MnO.