Growth of titanium dioxide thin films via a metallurgical route and characterizations for chemical gas sensors

Polycrystalline Al-doped rutile TiO2 were grown on quartz substrates by a novel metallurgical route and characterized by X-ray diffraction, and scanning electron microscopy and transmission electron microscopy. The role of Al is to generate non-stoichiometry and oxygen vacancies to make the rutile TiO2 matrix more conducting. Ti/(TiO2:Al) junctions were found to give linear current–voltage (I–V) characteristics after annealing at 400 °C for 30 min, showing good ohmic behaviour. Palladium Schottky contacts were fabricated on (TiO2:Al) and characterized by I–V measurements. The effect of operating temperature on junction parameters was studied. The sensor response of Pd/(TiO2:Al) junction was studied at 400 °C in presence of H2 gas with varying concentrations from 500 to 2000 ppm. The sensitivity, response time and reversibility were investigated from the transient response characteristics of the sensor at 400 °C. The sensitivity was found to be a function of applied bias across the junction.