High temperature stability of indium tin oxide thin films

Abstract A robust high temperature strain gage based on indium-tin-oxide (ITO) has been used to measure static and dynamic strains at temperatures up to 1400 °C. These thin film, ceramic strain gages have several advantages over metal strain gages including a large gage factor and increased chemical and electrical stability at very high temperatures. Electron spectroscopy for chemical analysis (ESCA) of ITO films deposited onto high purity alumina substrates and subjected to temperatures up to 1400 °C indicated that the ITO films had undergone an interfacial reaction with the substrate. In addition, the interfacial reaction appears to have been responsible for high temperature stabilization through the formation of an ITO/Al2O3 solid solution. When similar ITO films were deposited onto alumina with a platinum diffusion barrier, there was no evidence of an interfacial reaction. Thermodynamic calculations indicated that bulk ITO may not be stable in air ambients at temperatures above 1300 °C but the alumina substrates stabilized the ITO to temperatures well beyond this value.