Gas Sensing Studies of Multifunctional Metal Oxide: Undoped/doped TiO2 Nanomaterial and Thin Films

At Bhabha Atomic Research Centre, Sensing studies were carried out at room temperature, 100°C, 150°C, 200°C and 300°C. Sensing response at150°C is over 200% at 10 ppm which is encouraging from application point of view. Fabrication of a sensor array based on TiO2 and doped- TiO2 thin films was demonstrated. TiO2 thin films were deposited on LaAl2O3 substrates by pulse laser deposition. The as-grown films were characterized by XRD. The sensor array based on TiO2 thin film can be used for identifying H2S gas both qualitatively and quantitatively by a proper control over the process parameters, namely: operating temperature and surface modifications. The maximum sensor response (S=204) at optimal temperature (150°C) was obtained for pure TiO2 epitaxial thin film . A concentration profile at 150°C was recorded for generation of data bank.
The Nb-doping in TiO2 improves the conductivity of TiO2, mainly in high temperature range where the material is mostly sensitive to gaseous species.

Further from the present work it is clear that TiO2 thin films can be operated as a H2S sensor in ppm level in the range of 1- 50 ppm. The sensor based on TiO2 found to be faster response and recovery time.
It is well established that sensor response and selectivity of metal-oxide sensors can be improved by using different strategies, such as, doping with penta-valent or tri-valent material and making composites of metal-oxides. In particular, for ppm level H2S detection it has been demonstrated that selectivity can be greatly enhanced if the sensing element consists of random p-n junctions. single chemiresistive sensor is usually tailored to detect a single gas.

By: Nagmani

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