LAUSR

Abstract In this research work, titanium oxide (TiO2) thin films were grown on p-type (100) silicon substrate by thermal oxidation of RF sputtered titanium thin films in air ambient at various temperatures ranging from 500 °C to 950 °C. The XRD pattern revealed the evolution of a mixture of anatase and rutile phases at thermal oxidation temperature of 500 °C. At higher temperature (>500 °C), well oriented crystalline rutile phase was obtained for all the thermally oxidized TiO2 films. The average crystallite size of the oxidized films at 500 °C and 950 °C is estimated as 9 nm and 43 nm, respectively. The root mean square (RMS) surface roughness is found to be increased with the rise in oxidation temperature. The microstructural studies by Raman spectroscopy have also revealed a mixture of anatase and rutile peak at 500 °C. The morphological studies have revealed the enhancement in grain size with the increase in oxidation temperature with the appearance of distinct grain boundaries. The chlorpyrifos sensing behavior of the oxidized samples were carried out at room temperature. Chlorpyrifos is a neurotoxic organophosphate compound, which is most widely used as a pesticide in agricultural farm. Current-time (I-t) measurement of thermally oxidized Ti films was performed in order to detect the chlorpyrifos. A significant enhancement in the conductivity was observed with the introduction of chlorpyrifos vapors. From the current-time curve, the response and recovery time during chlorpyrifos sensing was evaluated to be around ~43 s and ~3.9 s, respectively.