Mahaveer Kumar Jain

In the present work, we describe the effect of crystallization on humidity sensing properties of nanocrystalline TiO2 thin films prepared by sol-gel techniques. Here, we report an enhancement in the relative humidity (RH) sensitivity just after the crystallization at 375 °C, which is attributed to increased surface activity near crystallization and lower crystallite size. After crystallization, the RH sensitivity was found to decrease with increasing grain size. The complex impedance of the sensor, measured using impedance spectroscopy, fits well with an equivalent circuit consisting of inter-granular resistance and capacitance in parallel. It was found that with the change in RH, only resistance changes significantly, when compared with the capacitance. © 2007 Elsevier B.V. All rights reserved.

In the present work, we describe humidity sensing properties of nano-structured multilayered TiO2:ZrO2 ceramic thin films prepared by sol-gel processing. An enhancement in the sensitivity is observed for both TiO2/ZrO2 (TZ) and ZrO2/TiO2 (ZT) thin film samples that are annealed at 400 °C, due to simultaneous crystallization of ZrO2 and TiO2. The multilayered ZrO2:TiO2 thin film shows less drift and low hysteresis compared to pure TiO2. The experimental data are fitted to an equivalent circuit containing a resistance and a non-Debye capacitance in parallel. Typical response and recovery time of the sensor are 56 and 124 s, respectively. We demonstrate the possibility of a practical device without heating the humidity sensitive element for regeneration. © 2007 Elsevier B.V. All rights reserved.

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. © 2007 IOP Publishing Ltd.