MEMS based hydrogen sensor with the highly porous Au-CNT film as a sensing material

Well dispersed gold nanoparticles were deposited on carbon nanotubes (CNTs) by direct current (DC) sputtering followed by dealloying method, forming highly porous thin films using nitric acid (HNO₃). The structure and morphology of the thin film were characterized using Fourier transmission-infrared spectroscopy (FT-IR), X-ray diffractometry (XRD), Raman spectroscopy, atomic force microscopy (AFM), and field emission scanning electron microscopy (FE-SEM). FE-SEM and AFM confirmed that gold nanoparticles were homogenously dispersed on the CNT matrix which is like a highly porous film. The XRD patterns revealed the existence of metallic gold particles on the disordered graphitic phases. FTIR and Raman spectroscopy confirmed the interaction between the gold nanoparticles and CNT matrix. A microelectromechanical systems based micro hydrogen gas sensor was developed from the highly porous thin film of Au-CNT. The micro heater and sensing electrode were fabricated to have a co-planar structure with a Pt layer. The designed micro platform showed low power consumption of 72 mW at a 2.5 V heater voltage and an operating temperature of 300 °C. The dimensions of the micro hydrogen gas sensor platform and sensing area were approximately 1.8 mm × 1.8 mm and 0.6 mm × 0.6 mm, respectively. The maximum gas sensitivity measured at 3.0 V was found to be 2.99%.