Effect of polyethylene glycol additive in sol on the humidity sensing properties of a TiO2 thin film

We describe the effect of polyethylene glycol ( PEG) addition to the precursor solution on the humidity sensing properties of a TiO2 thin film. Thin films of TiO2 were prepared by sol-gel and spin coating techniques. An increase in humidity sensitivity has been observed after the addition of PEG. This increase in sensitivity is due to smaller crystallites and pores created during the combustion of the polymer. The response and recovery time of the sensor were about 10 and 176 s, respectively. An equivalent circuit has been proposed and fitted well with the experimental data. We demonstrate that a controlled amount of polymer addition leads to the sensor being highly sensitive in the lower humidity (< 40% RH) region.