Chukwudike Ukeje¹, Bruno Rente¹, Mark Vaughan¹, Ignacio Llamas², Zabdiel Brito², Jung Mu Kim³, Peter Petrov^1
1Imperial College London, London, United Kingdom
²Centre Tecnológico de Telecommunication de Catalunya (CTTC), Catalunya, Spain
³Jeonbuk National University, South Korea
Hydrogen detection remains essential for applications in clean energy and safety monitoring, where sensor performance heavily depends on the microstructural properties of the active material. Palladium (Pd) thin films are extensively studied for hydrogen sensing because of their high solubility and selective hydrogen absorption. In this study, we systematically examine how substrate temperature during electron beam deposition affects the growth, structure, and sensing response of Pd thin film sensors utilized for hydrogen detection. Palladium thin films were deposited at different substrate temperatures, and their grain size, morphology, and electrical resistivity were analysed. Results indicate that deposition temperature notably alters grain size and film density, which influence hydrogen absorption kinetics. These microstructural changes directly affect sensing performance, including sensitivity, hysteresis behaviour, and response/recovery times of the characterized sensor. At lower deposition temperatures, nanocrystalline features were observed, enhancing sensor sensitivity. Conversely, higher deposition temperatures led to an increase in grain size, resulting in faster response and recovery times but with decreased sensitivity compared to deposition at ambient conditions. These findings highlight the importance of controlling deposition temperature to optimize thin film palladium hydrogen sensors and offer valuable guidance for tailoring sensor properties to demanding application environments.