Development of NiCoCrFePd high-entropy alloy thin films for high-temperature NO₂ gas sensing

Abstract High-entropy alloy thin films (HEATFs) have garnered a lot of interest lately because of their superior chemical and physical characteristics as well as their potential applications in a wide range of advanced technology industries, including nano-electronics, medical, aerospace, gas sensors, and nuclear energy. Gas sensors fabricated using HEATFs are not only stable at elevated temperatures but also crucial for industrial safety and environmental monitoring under extreme conditions of high temperature and radiation. Among these, the detection of nitrogen dioxide (NO₂) is of significant importance due to its highly toxic and reactive nature. Here, the sensing response of the HEATF of NiCoCrFePd deposited using the pulsed laser deposition technique is presented. Grazing incidence x-ray diffraction (GIXRD), energy dispersive x-ray (EDX), x-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and x-ray reflectivity techniques are used to examine the composition, surface morphology, and structural characteristics of HEATFs. XRD along with SEM analysis confirmed the formation of single-phase face-centered cubic (FCC) with nanoscale granules. XPS investigation confirmed the presence of O at the surface. The NO₂ gas-sensing performance of the NiCoCrFePd HEATFs sensor is analyzed with 50–200 ppm at an elevated temperature of 130 °C. The observation of high sensitivity at high temperatures and a quick response time (66 sec) indicate that NiCoCrFePd HEATFs have great potential in the effective detection of NO₂ in high-temperature environments. Thus, this study will open new avenues for the development of HEATF-based reliable gas sensors under extreme conditions.