An efficient BTX sensor based on p-type nanoporous titania thin films

Abstract

Sensing performance of sol–gel synthesised p-titania based sensors towards detection of low concentrations (⩽1 ppm) of benzene, toluene and xylene (BTX) at low temperature range (50°–175 °C) is presented in this article. The sensing layer was grown by dip coating method using oxidized silicon wafer as the substrate. X ray diffraction (XRD) analysis confirmed the growth of anatase phase of TiO2 with 〈1 0 1〉 preferential orientation. Nanoporous nature of the film was observed from Field Emission Scanning Electron Microscope (FESEM). Through Hall measurement, p-type conductivity of the TiO2 layer was authenticated. Sensing performance of the sensing layer to BTX was investigated in resistive mode with two lateral titanium electrodes. At low concentration range (0.1–1 ppm) of individual vapor of BTX, the sensing performance of the sensor was investigated found to be very promising. The results indicated that the optimum operating temperature for BTX sensing is moderately low (75 °C), with appreciably fast response and recovery time. At the lowest concentration (0.1 ppm) the corresponding response/recovery time was found to be ∼24 s/12 s, ∼14 s/20 s and ∼20 s/14 s for benzene, toluene and xylene respectively, at 75 °C. The influence of relative humidity (20% and 75%) on the sensing parameters of the developed sensor device has also been investigated. Possible sensing mechanism of detection of these aromatic hydrocarbons on p-type nanoporous titania surface is also discussed elaborately.