Two-dimensional (2D) nanostructured materials such as reduced graphene oxide (rGO) are highly promising for hydrogen (H2) sensing due to their narrow bandgap, number of active sites, and high surface area. Detection of hydrogen gas, a renewable and clean source of energy, in the atmosphere is of great importance in maintaining safety at all stages of hydrogen production, storage and use. In this work, a novel conductometric sensor has been developed based on hybrid 2D nanostructured rGO doped with Pd nanoparticles (Pd/rGO) to evaluate its sensing performance towards hydrogen with different concentrations (up to 1%). Various sensing parameters including sensitivity, response/recovery time, stability, and low detection limit have been investigated throughout the experiment. We also evaluate performance of the developed sensors at different operating temperatures (room temperature up to 120°C). Material properties of hybrid Pd/rGO film including surface morphologies, crystallinity, molecular vibration, functional groups, and oxidation states are sufficiently analysed by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX), profilometer, X-ray diffraction (XRD), and Raman spectroscopy. Furthermore, fundamental sensing mechanism governing the interactions between Pd/rGO and the hydrogen molecules are studied. It is anticipated that materials and techniques described in this work offers solutions to develop highly sensitive and portable hydrogen sensors with low power consumption and low fabrication and operation cost.
Pt/anodized TiO2/SiC based metal-oxide-semiconductor (MOS) devices were fabricated and characterized for their
sensitivity towards propene (C3H6). Titanium (Ti) thin films were deposited onto the SiC substrates using a filtered
cathodic vacuum arc (FCVA) method. Fluoride ions containing neutral electrolyte (0.5 wt% NH4F in ethylene glycol)
were used to anodize the Ti films. The anodized films were subsequently annealed at 600 °C for 4 hrs in an oxygen rich
environment to obtain TiO2. The current-voltage (I-V) characteristics of the Pt/TiO2/SiC devices were measured in
different concentrations of propene. Exposure to the analyte gas caused a change in the Schottky barrier height and hence
a lateral shift in the I-V characteristics. The effective change in the barrier height for 1% propene was calculated as
32.8 meV at 620°C. The dynamic response of the sensors was also investigated and a voltage shift of 157 mV was
measured at 620°C during exposure to 1% propene.
Zinc oxide (ZnO) is one of the most promising electronic and photonic materials to date. In this work, we present an
enhanced ZnO Schottky gas sensor deposited on SiC substrates in comparison to those reported previously in literature.
The performance of ZnO/SiC based Schottky thin film gas sensors produced a forward lateral voltage shift of 12.99mV
and 111.87mV in response to concentrations of hydrogen gas at 0.06% and 1% in air at optimum temperature of 330 ºC.
The maximum change in barrier height was calculated as 37.9 meV for 1% H2 sensing operation at the optimum