Stability enhancement of the nitrogen-doped ITO thin films at high temperatures using two-step mixed atmosphere annealing technique

[Display omitted] •Two-step mixed atmosphere annealing technique was developed .•Stable crystal structures and chemical states of the ITON thin films can be formed.•Good TCR repeatability and high piezoresistive stability at 1200 °C were observed .•The influence mechanism of the annealing technique on the stability of ITON thin films were unveiled. Two-step mixed atmosphere annealing was developed to enhance the stability of the nitrogen-doped ITO (ITON) thin films at high temperatures. The ITON thin films were first annealed in nitrogen and then were subjected to the second-step annealing in the air (N2-air) and vacuum (N2-vacuum) environment at 1000 °C, respectively. Results show that stable microstructures and chemical states can be obtained by this two-step annealing method due to the formation of the stable metal oxynitrides and the repair of the oxygen deficiencies. Comparatively, the N2-air ITON thin film has more advantages in maintaining the property stability at high temperatures than that of the N2-vacuum ITON thin film. The N2-air ITON thin film has the lower TCR volatility rate (TVR) of 2.4% at 1200 °C and the smaller resistance drift rate (DR) of 0.004 /h at 1000 °C. Besides, a more stable gauge factor (GF) was also observed in the N2-air ITON TFSG during the piezoresistive cycle test at 1000 °C. These can be attributed to the more complete repair of the oxygen deficiencies when conducting the second-step annealing in the air.