Piezoresistive failure behaviors and mechanisms of the ITO thin films at high temperatures

Abstract

ITO is drawing enormous attention in fabrication of thin film strain gauges (TFSGs) due to its excellent oxidation resistance, high melting point and great piezoresistivity. However, the operating temperature of ITO TFSGs is far lower than its melting point. In this work, 8.9 μm ITO thin films and TFSGs were prepared using magnetron sputtering to reveal their piezoresistive failure behaviors and mechanisms at various high temperatures. Results show that surface bulges and significant thickness reduction of the ITO thin films appear at 1275 °C due to their repaid sublimation. The Hall mobility of the ITO thin films decreases sharply due to the formation of the surface bulges and significant thickness reduction at 1275 °C. The piezoresistive failure behaviors of the ITO TFSGs mainly result in their significant resistance drift and the decline of the gauge factor (GF) at 1275 °C. The drift rate of the ITO TFSG at 1275 °C is nearly 7 times higher than that at 1250 °C. The GF of the ITO TFSGs drops from 4.67 to 1.77 when the testing temperature rises from 1250 °C to 1275 °C. These can be attributed to the sharp decrease of the Hall mobility of the ITO thin films.