The effect of metal electrodes and deposition angle on linearity of sculptured TiO₂ humidity microsensors

In this work, the sensitivity and linearity properties of capacitive based titanium dioxide (TiO₂) humidity microsensors with different materials used as electrodes have been investigated. The TiO₂ thin films were grown on either Ti or TiN microinterdigitated structure as contact electrodes utilizing glancing angle deposition (GLAD) electron beam evaporator. The crystallinity and surface morphology of the prepared thin films were characterized by field emission scanning electron microscope (FE-SEM). The anatase phase structure of TiO₂ thin films and the porous-like nanocrystalline TiO₂ films sculptured by GLAD has been observed. The sensitivity of TiO₂/Ti-electrode and TiO₂/TiN electrode humidity sensors have been measured by current–voltage and capacitance–voltage. The capacitive sensors with Ti electrodes show better sensitivity and linearity than the sensors with TiN electrodes. The results show that the sensitivity of 1.17 × 10^–11 F/%RH and linearity of 0.97 were achieved for our sensor with Ti microinterdigitated electrodes and porous-like nanocrystalline TiO₂ films grown at 70° glancing angle.