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

Mesoporous silica thin films have been prepared using a self-assembling process employing cetyltrimethylammonium bromide (CTAB) as the organic template. The films were deposited by dip-coating on silicon and alumina substrates. Thermal treatment at 250 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.