Optical Properties of CdPbSe Thin Films: Effects of Deposition Process and Alloy Composition

Abstract This study investigates the role of lead (Pb) ions in the synthesis of cadmium-lead-selenium (CdPbSe) alloyed thin films within an alkaline environment. The research focuses on how the deposition process and alloy composition influence the optical properties of the resulting thin films. The findings reveal that Pb is not merely an impurity in CdPbSe but plays a crucial role in determining their optical characteristics. Notably, a Pb concentration of 0.03 mol was found to enhance optical transitions in the infrared region, highlighting the potential of alloying as a strategy to engineer quantum dots with tailored properties for optoelectronic applications and beyond.Alloyed quantum dots offer a versatile platform for designing advanced nanomaterials, enabling precise control over their optical and electronic properties. By exploring the relationship between alloy composition, deposition parameters, and optical behavior, this work opens new possibilities for advancing this innovative technology.Deposition time is a critical factor influencing the energy gap of quantum dots. It was observed that longer deposition durations are associated with a reduction in the energy gap, potentially indicating an increase in nanoparticle size. This observation aligns with principles of semiconductor physics, where larger particles typically exhibit smaller energy gaps due to quantum confinement effects. However, contrary to the expected trend of decreasing energy gaps with increasing particle size, an unexpected rise in lead ion concentration was observed as deposition time increased. This finding challenges the assumption that nanoparticle size alone dictates the energy gap, suggesting that ion incorporation dynamics during deposition may significantly affect optical properties.Furthermore, electron microscopy images failed to provide clear evidence of nanoparticle growth, raising questions about the reliability of visual methods for assessing size changes at the nanoscale. This suggests that the mechanisms governing growth or structural transformations may be more complex than previously understood.To determine the bandgap energy without relying on assumptions about the semiconductor's structure, we employed the Derivation of the Ineffective Method (DITM), which offers a more robust alternative to the Tauc model.Overall, the analysis underscores the importance of metal ion concentration, particularly lead in regulating the energy bandgap of quantum dots. This shifts the focus from solely considering size-dependent properties to examining the chemical composition and ion dynamics throughout the deposition process, providing a more comprehensive understanding of quantum dot behavior.