Effect of substrate temperatures on BaCo.1Bi.9O3 NTC thermistor thin films

BaCo.1Bi.9O3 thin films were successfully prepared by reactive RF magnetron sputtering at different substrate temperature. Crystalline structures, surface morphologies and electrical properties were analyzed by XRD, AFM and resistivity-temperature spectrum. Co ion diffused into the lattice of BaBiO3 to form a solid solution with monoclinic perovskite structure. The root-mean-square value of surface roughness was ~ 4.2 nm for the BCB film deposited at 200 ℃. All thin films exhibited good negative temperature coefficient (NTC) thermistor characteristics. The values of B25/85, a25 and ρ25 of BaCo.1Bi.9O3 thin films were in the range of 2538-2730 K, −3.07 to −2.86% K−1 and 345.6-34634.4 Ω cm, respectively. The optimal NTC characteristic (B25/85 = 2730 K) with ρ25 of 345.6 Ω cm was presented in the BaCo.1Bi.9O3 thin films grown at 200 ℃ for 4 h. Grains and grain boundaries of BaCo.1Bi.9O3 films also showed typical NTC thermistor behavior.