Electrical properties of sputtered RuO 2 films

Abstract

RuO 2 films about 40–700 nm thick were prepared from a RuO 2 powder target by RF sputtering in an atmosphere of argon, and their crystal structure and their electrical properties were investigated. The crystallinity of the sputtered RuO 2 films was found to depend on the sputtering power density and the film thickness. At the power density of 3.1 W cm -2, the films with thickness greater than 110 nm showed X-ray diffraction peaks corresponding to RuO 2 (110) and (211) planes. The crystallinity of the sputtered films increased with an increase in the power density. The electrical resistivity of the RuO 2 films was higher than the bulk value by about one order of magnitude. The RuO 2 films with higher crystallinity tend to have lower resistivities. Temperature dependences of the resistivities were also measured. It was found that the RuO 2 films prepared at high power density showed positive TCR, while the specimens prepared at low power density showed negative TCR, and the specimen prepared at 2.3 W cm -2 showed a TCR of zero. These results can be explained by a model in which the sputtered RuO 2 film consists of microcrystalline RuO 2 grains dispersed in amorphous RuO 2 matrix. The amorphous RuO 2 is considered to have a negative TCR.