Influence of controlled preheating on the physical properties of nanoscale cadmium oxide thin films

Abstract Herein, we report a comprehensive analysis of dependence of pre-heating temperature on CdO thin films deposited on glass substrates via sol-gel spin coating method. This study investigates the impact of pre-heating temperatures on the physical properties of CdO thin films. XRD confirmed a polycrystalline structure with good crystallinity. SEM showed smooth and uniform surface, while AFM revealed increased surface roughness due to enhanced coalescence. Optical studies showed that the films remained transparent, with a slight decrease in band gap from 2.57 eV to 2.46 eV. PL indicated the presence of defects like oxygen vacancies, which contribute to electrical conductivity. XPS spectroscopy analysis showed that the Cd3d core spectra split into Cd3d 5/2 and Cd3d 3/2 . Hall effect results confirmed n-type conductivity with low resistivity of 10⁻ 3 Ω-cm. Although the 150 °C film shows a higher figure of merit, the 200 °C sample offers the most optimized combination of optical transmittance and electrical conductivity, making it the superior choice overall. Thus, our findings indicate that choice of proper pre-heating temperature is optimal for the growth of CdO thin film making it an ideal candidate for device applications.