A nanoporous thin-film miniature interdigitated capacitive impedance sensor for measuring humidity

This paper presents a development of a low-cost miniature humidity sensor with an interdigitated aluminium electrode connected in parallel on quartz substrate. Interdigitated capacitive device has been fabricated using the photolithography method. The aluminium electrode was covered with sensitive film of a nanoporous thin film of γ-Al2O3 made from novel sol–gel technique. Nanostructured thin film offers very high surface to volume ratio with distribution of micro pores for moisture detection. Pore morphologies of the film have been studied by field emission electron microscope and X-ray diffraction methods. Impedance measurement of the miniature capacitive humidity sensor toward relative humidity was investigated at room temperature by Agilent 4294A impedance analyzer (Agilent, Santa Clara, CA, USA). The device exhibits short response and recovery times and good repeatability.