Structure Effect on the Response of ZnGa2O4 Gas Sensor for Nitric Oxide Applications

Abstract

We fabricated a gas sensor with a wide-bandgap ZnGa2O4 (ZGO) epilayer grown on a sapphire substrate by metalorganic chemical vapor deposition. The ZGO presented (111), (222) and (333) phases demonstrated by an X-ray diffraction system. The related material characteristics were also measured by scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. This ZGO gas sensor was used to detect nitric oxide (NO) in the parts-per-billion range. In this study, the structure effect on the response of the NO gas sensor was studied by altering the sensor dimensions. Two approaches were adopted to prove the dimension effect on the sensing mechanism. In the first approach, the sensing area of the sensors was kept constant while both channel length (L) and width (W) were varied with designed dimensions (L × W) of 60 × 200, 80 × 150, and 120 ×100 μm2. In the second, the dimensions of the sensing area were altered (60, 40, and 20 μm) with W kept constant. The performance of the sensors was studied with varying gas concentrations in the range of 500 ppb~10 ppm. The sensor with dimensions of 20 × 200 μm2 exhibited a high response of 11.647 in 10 ppm, and 1.05 in 10 ppb for NO gas. The sensor with a longer width and shorter channel length exhibited the best response. The sensing mechanism was provided to explain the above phenomena. Furthermore, the reaction between NO and the sensor surface was simulated by O exposure of the ZGO surface in air and calculated by first principles.

Growth and Characterization of Sputtered ZnO:ZnGa2O4 Dual-Phase Films on Sapphire Substrates for NO Gas-Sensing Applications

“…Therefore, the potential barrier at grain boundaries enhances, resulting in the increment of resistance even further. 46 In general, the loss of electrons in sensors will increase the width of the charge depletion region, increasing its resistance, indicating that oxidizing gas will increase the resistance of n-type gas sensors. In contrast, this gas sensor demonstrated dramatically reduced response time and recovery time due to smaller grain size and grain boundaries.…”

“…Since NO molecules have a higher electron affinity (2.28 eV) than oxygen molecules (1.46 eV), they interact with adsorbed oxygen ions on the ZnO:ZnGa 2 O 4 surface. Therefore, the potential barrier at grain boundaries enhances, resulting in the increment of resistance even further . In general, the loss of electrons in sensors will increase the width of the charge depletion region, increasing its resistance, indicating that oxidizing gas will increase the resistance of n-type gas sensors.…”

Ppb-Level Hydrogen Sulfide Gas Sensor Based on the Nanocomposite of MoS2 Octahedron/ZnO-Zn2SnO4 Nanoparticles

“…Several gas sensors based on SMOs such as zinc oxide (ZnO), zinc gallate (ZnGa 2 O 4 ), tin oxide (SnO 2 ), nickel cobaltite (NiCo 2 O 4 ), zinc stannate (Zn 2 SnO 4 ), copper oxide (CuO), etc., possess some good properties such as precision, low cost, small dimensions, long-term stability and environmental friendliness; because of these properties, SMOs could be considered the primary candidates for the detection of toxic gases as well in photo-catalysis, etc. [ 4 , 5 , 6 , 7 , 8 , 9 , 10 ]. Plenty of research has shown that some complex metal oxides have been widely used as gas sensors in the last decades.…”