Work

Anion-engineered CsInTiS₄₋ₓOₓ (x = 0.8) quantum dots for enhanced nonlinear photonics and optoelectronics

Year: 2026

Type: article

Abstract: Computational modelling of anion-substituted quantum dots reveals that controlled oxygen incorporation into CsInTiS₄ nanostructures induces profound modifications in electronic structure and optical response. Therefore, in our study, we examined 20% anion-site oxygen incorporation into CsInTiS 4 (i.e., CsInTiS 3.2 O 0.8 QDs) using methods based on density functional theory and dielectric function optical modelling. Our results regarding structural relaxation and simulated X-ray diffraction indicate that sulfur’s substitution with oxygen induces lattice contraction and structural reorganization. This is accompanied by a change in the lattice symmetry from polar $\:{P}_{21}$ to centrosymmetric P 2/m in the optimized geometry. CsInTiS₃.₂O₀.₈ exhibits a pronounced bandgap contraction from $\:2.22$ $\:\text{e}\text{V}$ in CsInTiS₄ to $\:0.69\:\text{e}\text{V}$ , whilst the optical carrier concentration-to-effective mass ratio increases by $\:74\%$ to $\:1.08\: \times \:\:{10^{52}}\:k{g^{ - 1}}\:{m^{ - 3}}$ . Furthermore, it reveals a Wemple–DiDomenico dispersion energy of $\:45.27\:\text{e}\text{V}$ , an oscillator strength of $\:455\:{\text{e}\text{V}}^{2}$ , a static refractive index of $\:2.35$ , and a high-frequency dielectric constant of $\:5.51$ . Moreover, carrier dynamics characterised by an ultrafast relaxation time of $\:1.22\: \times \:\:{10^{ - 16}}s$ point to dominant scattering pathways intrinsic to the mixed-anion framework. These findings suggest that oxygen anion substitution plays a viable role in band structure engineering and light–matter interactions in a CsInTiS₄ parent lattice. Thus, the predicted narrow band gap, enhanced light–matter interaction, and oscillator strength make CsInTiS₃.₂O₀.₈ a strong candidate for infrared photodetection, tunable plasmonics, and third-order nonlinear photonics.

Source: Scientific Reports

DOI: 10.1038/s41598-026-59279-z

Authors: M. S. El-Bana, Abdullah Alsulami, M. A. M. El-Mansy

Institution: Qassim University

Language: English

Topic: Quantum Dots Synthesis And Properties

Subfield: Materials Chemistry

Field: Materials Science

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $2,690

Funder: Qassim University