Influence of Multi-Layered CdO Thin Films on Their Ability to Detect Toxic Gases

Abstract

This research investigates the influence of a number of coated layers on the gas-sensing properties of cadmium oxide (CdO) thin films prepared using the spin coating technique on glass substrates. Structural examinations, including X-ray diffraction (XRD), revealed a consistent cubic polycrystalline nature. Atomic Force Microscopy (AFM) elevated roughness and grain sizes with increased layering. Scanning Electron Microscopy (SEM) showcased a cauliflower-like morphology on the films. The optical band gap also narrowed marginally from 2.65 eV (2-layer) to 2.53 eV (5-layer). Hall effect studies confirmed n-type conductivity, with enhanced mobility. Gas sensing assessments identified the 5-layer CdO film, termed CD-4, as highly responsive to H₂S, achieving 72% sensitivity at 200°C and a swift 14-second response. This work elucidates CdO film gas-sensing dynamics, emphasizing layer optimization's significance.