Development of a high-performance chemiresistive H₂S sensor based on sandwich type SnO2: CuO film realized using hybrid PVD approach

This study presents the development of a high-performance chemiresistive hydrogen sulphide (H₂S) gas sensor realized using a hybrid physical vapor deposition (PVD) technique. In particular, the sensor fabrication process integrates two complementary PVD methods; namely Direct Current (DC) sputtering for tin (Sn) deposition and thermal evaporation for copper (Cu) deposition, forming a heterostructured sensing layer that exhibited enhanced gas adsorption and charge transfer properties. The developed sensor exhibited a sensor response (SR) of 22,000 (Ra/Rg) towards 500 ppm of H2S with a rapid response and recovery times of 1 and 6 min, respectively. The sensor performance was evaluated against the 4-S sensor selection or Ramgir criteria to check its feasibility for commercial deployment. Identical response kinetics observed over multiple cycles or repeated high-concentration H₂S exposure (500 ppm) further establishes the excellent repeatability and reproducibility thereby assuring reliability of the developed sensors. Further, the long-term operational stability measurements assessed over a period of six months indicated that the sensor consistently maintained a SR of 2200 towards 10 ppm H2S with negligible degradation. Selectivity studies revealed that the sensor exhibited a significantly higher response toward H₂S compared to other interfering gases, including methane (CH₄), chlorine (Cl₂), ammonia (NH₃), and ethylene (C₂H₄). The synergistic combination of Sn and Cu, deposited via the dual PVD approach, significantly enhances the sensor’s sensitivity, selectivity, and durability. The fulfilment of the 4-S sensor selection criteria makes the sensor a promising candidate for realizing a device suitable for industrial and environmental H₂S monitoring applications.