Capacitive response of nanoporous HMDSO film coated interdigited electrodes towards VOCs molecules

In this paper, nano-porous thin films capacitive-type sensors have been fabricated for the detection of volatile organic compounds (VOCs) using the micro sized interdigitated electrodes (IDEs). The sensitive layers were elaborated from hexamethyldisiloxane (HMDSO) using plasma enhanced chemical vapor deposition (PECVD) technique. The choice of HMDSO polymer as sensitive layer is based on its low dielectric constant compared to analytes ones. The sensing performances of plasma polymers were strongly correlated to their chemical and physical properties, which depend directly on the plasma polymerization conditions including monomer pressure. The sensor sensitivity was at its highest value of 0.32, 0.24 and 0.20 pF/ppm towards methanol, ethanol and acetone, respectively, for the device fabricated with the smallest gap (36 µm) and higher monomer pressure (50 Pa). Chemical and morphological structures of the elaborated thin sensitive layers have been investigated by Fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM) and scanning electron microscope (SEM), respectively.