Electrical and structural characterization of mesoporous silica thin films as humidity sensors

Mesoporous silica thin films have been prepared using a self-assembling process employing cetyltrimethylammonium bromide as the organic template. The films were deposited by dip-coating on silicon and alumina substrates. Thermal treatment at 250º and 450 °C was used to remove the organic template. Fourier transformed infra-red spectra demonstrated that calcination is complete at 450 °C. Electrical measurements under dry and wet conditions were performed for films deposited on alumina substrates with comb-type gold electrodes. The films showed an increase in current intensity as a function of relative humidity. No memory effects were observed after cyclic testing in dry-wet conditions. Electrical characterisation indicates that the mesophase is easily accessible by the external environment.