Capacitive humidity sensing properties of freestanding bendable porous SiO2/Si thin films.

The fabrication of freestanding bendable films without polymer substrates is demonstrated as a capacitive humidity-sensing material. The bendable and porous SiO2/Si films are simply prepared by electrochemical-assisted stripping, metal-assisted chemical etching, followed by oxidation procedures. The capacitive humidity-sensing properties of the fabricated porous SiO2/Si film are characterized as a function of the relative humidity and frequency. The remarkable sensing performance is demonstrated in the wide RH range from 13.8 to 79.0%. The sensing behavior of the porous SiO2/Si film is studied by electrochemical impedance spectroscopy analysis. Additionally, the reliability of the porous SiO2/Si sensing material is confirmed by cyclic and long-term sensing tests.