Nano‐Patterned CuO Nanowire Nanogap Hydrogen Gas Sensor with Voids

Abstract Hydrogen (H ₂ ) is increasingly employed in industrial applications, such as developing hydrogen fuel cells for vehicles and power plants. However, H ₂ explodes at a concentration limit of 4%, necessitating the development of ultrasensitive hydrogen sensors capable of early‐stage detection of hydrogen leaks. In this study, nano‐patterned polycrystalline cupric oxide (CuO) nanowire array nanogap gas sensors with voids are fabricated using electron‐beam lithography and ex situ oxidization by annealing, which could detect 5 ppb H ₂ and show response and recovery times of less than 10 s without a baseline shift. Combining a pre‐H ₂ annealing process in Ar/H ₂ for Cu nanowires and a low‐rate oxidation process enhances the crystallinity of CuO nanowires, facilitating the preparation of polycrystalline CuO nanowires with voids, which is a significantly practical approach for the improvements of gas sensing properties. Response and recovery times of <10 s can be obtained for a gap separation of ≈30 nm. These improvements are discussed based on a high electric field of ≈1.3 MV cm ⁻¹ . The relationship between the normalized response and H ₂ concentration is discussed based on the power law. This paper presents highly reliable and fast H ₂ sensors without a baseline shift to meet the demands of the hydrogen industry.