Fabrication of binary and ternary semiconductors as gas sensing devices: stoichiometric design and functional engineering studies

Abstract

Metal-oxide semiconductor (MOS) sensors play a key role in environmental monitoring, healthcare diagnostics, and industrial safety due to their robustness, scalability, and low fabrication cost. However, achieving reliable selectivity and stability under realistic conditions remains a major challenge, often limited by the interplay between material composition, defect chemistry, and synthesis-dependent microstructure. To address this issue, the present work investigates the Zn–Sn–O ternary system as a tunable materials platform for CO and acetone sensing, focusing on how synthesis route and stoichiometry influence structural and functional behavior. Three complementary fabrication methods were employed to produce Zn–Sn–O materials with controlled composition and morphology: physical vapor deposition by magnetron sputtering (PVD-RMS), ultrasonic spray pyrolysis (USP), and chemical co-precipitation (CP). Each method provided distinct thermodynamic and kinetic environments that governed phase formation, crystallinity, and grain morphology. The synthesized materials were systematically characterized through X-ray diffraction with Rietveld refinement, FTIR and Raman spectroscopy, XPS, and SEM/EDS to correlate synthesis conditions with crystal structure and surface features. Gas-sensing performance toward CO and acetone was evaluated using a custom-built dynamic sensing system under standardized temperature and concentration ranges, allowing direct comparison across thin-film and powder-based architectures. Among the tested samples, the SZ50-450-USP thin film exhibited the highest acetone sensing performance at 300 °C, with response and recovery times of 193 s and 207 s, respectively, and a maximum sensing response of 87 %. These results demonstrate that balanced Zn/Sn ratios and controlled microstructural evolution significantly enhance sensitivity and stability. Based on the structural and functional analyses, a sensing mechanism is proposed that links preferential crystallographic orientation, grain size, and oxygen-vacancy distribution to the adsorption–desorption dynamics of target gases. The comparative study highlights the importance of synthesis–structure–property relationships in optimizing gas-sensing performance and provides a reproducible framework for designing Zn–Sn–O-based semiconducting oxides for selective VOC detection, with potential applications in medical diagnostics via breath analysis.