Development and electrical properties of wurtzite (Al,Ti)N materials for thin film thermistors

Nitride thin-film materials are deposited on resin substrates for application as flexible thin-film temperature sensors. Highly crystalline wurtzite (Al,Ti)N films deposited on polyimide substrates offer both negative temperature coefficient properties and flexibility. Thermistor constants (B values) are analyzed by measuring the temperature dependence of the electrical resistivity, Hall resistivity, and thermoelectric power. The B value is found to largely depend on the nitrogen content rather than on the titanium content in (Al,Ti)N, which suggests that electrical conduction through nitrogen atoms plays an important role in thermistor properties. The difference in electrical conduction mechanism between nitrides and oxides is also discussed on the basis of the analysis.