Effect of doping (Sn and In) on CdS thin films for ammonia sensing at room temperature

Abstract

The quantification and detection of Ammonia (NH3) are crucial due to their direct impact on human health and the environment, particularly when concentrations exceed 50 ppm in the atmosphere. To address this, thin films of pure CdS, Sn-doped CdS (CdS:Sn), In-doped CdS (CdS:In), and co-doped Sn and In (CdS:Sn:In) were prepared using the nebulized spray pyrolysis technique (NSP) for NH3 sensing studies. The X-ray diffraction (XRD) substantiated the single phase and polycrystallinity of the prepared films. Atomic Force Microscopy (AFM) reveals that CdS:In film attained higher RMS, average roughness, skewness (Rsk), and Rku values than the other prepared films. The estimated optical bandgap energy value is 2.44 eV for the CdS:In film. The photoluminescence (PL) studies reveal that the presence of defects. Emission bands observed around 523.35 nm, and 681 nm are attributed to band-to-band transition, and exciton recombination between sulphide vacancies (Vs2+) and the VB respectively. Essentially, the X-ray photoelectron spectroscopy (XPS) analysis reveals the existence of surface elements in various oxidation states. Surpassing the performance of other prepared films, CdS:In exhibited an exceptional response of 604.98 at 250 ppm, long-term stability and good repeatability, with rapid response and recovery times of 43.09 s and 5.6 s respectively.