Capacitive humidity-sensing properties of electron-beam-evaporated nanophased WO3 film on silicon nanoporous pillar array

A regularly arrayed WO3/Si nanostructure was prepared through evaporating nanophased WO3 film on silicon nanoporous pillar array (Si-NPA). X-ray diffraction measurements disclosed that the deposited WO3 film was of pure triclinic phase and the average grain size was estimated to be ∼26.4 nm. A capacitive humidity sensor with coplanar interdigital electrodes was fabricated based on WO3/Si-NPA. With the relative humidity (RH) being changed from 11% to 95%, a sensitivity over 16,000% was achieved at an optimal measuring frequency of 1000 Hz. The response and recovery times were determined to be ∼104 and ∼94 s, respectively, with the maximum humidity hysteresis being ∼5.3% at 65% RH. Our results indicate WO3/Si-NPA might be a promising sensing material for fabricating practical humidity sensors.