Tailoring structural and optical properties of CdSe thin films deposited with nominal Tb³⁺ precursor concentrations (0–10 mol%) via chemical bath deposition

Abstract

Cadmium selenide (CdSe) thin films were deposited on glass substrates by chemical bath deposition using nominal Tb³ ⁺ precursor concentrations of 0 –10 mol% at 80 °C. The influence of increasing Tb precursor concentration on the structural, morphological, and optical properties of the deposited CdSe films was systematically investigated. X-ray diffraction analysis revealed a progressive evolution from a mixed hexagonal/cubic structure toward a predominantly cubic zinc-blende CdSe phase with increasing Tb³ ⁺ concentration. Raman and Fourier-transform infrared studies confirmed phonon softening and increased lattice disorder due to dopant-induced strain. Morphological analyses (scanning electron microscopy and atomic force microscopy) showed enhanced grain cluster growth and surface roughness at moderate doping levels, followed by slight deterioration at higher concentrations. Representative energy dispersive X-ray Spectroscopy and X-ray Photoelectron Spectroscopy analyses confirmed successful incorporation of Tb into the CdSe lattice, although the incorporated Tb concentration was considerably lower than the nominal precursor concentration employed during synthesis. Optical studies indicated a significant band gap reduction from 1.86 eV (undoped) to 1.31 eV upon doping, attributed to impurity levels and band tailoring. Photoluminescence spectra revealed dominant defect-related emissions in the blue region, with stable chromaticity coordinates across most doping levels. The results demonstrate that Tb³ ⁺ doping effectively tailors the structural and optical properties of CdSe thin films, making them promising candidates for tunable optoelectronic and light-emitting applications.