Role of film thickness on the microstructure and electrical properties of Mn-Co-Ni-O thin film thermistors

Mn1.85Co0.3Ni0.85O4 (MCN) thin film thermistors with different film thickness (in the range of 400-750 nm) were prepared on Al2O3 substrates by sol-gel technique. The effects of film thickness on the microstructure and electrical properties of the prepared thin film thermistors were investigated by XRD, FESEM, resistance-temperature measurements and Hall measurements. The results showed that MCN thin film thermistors were of good crystallization and compact surface, and the carrier concentration was independent on the thickness. The resistance measured at room temperature was almost linearly decreasing with the increase of thickness. The sensitivity and activation energy increased slightly, then, the aging coefficient decreased sharply with the film thickness increasing.