Effect of composition ratio on the structural and optical properties of MnS@ZnS nanocomposites
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Effect of composition ratio on the structural and optical properties of MnS@ZnS nanocomposites Zein K. Heiba1 · Mohamed Bakr Mohamed1,2 · S. I. Ahmed1,3 · A. M. El‑naggar1,4 · AA. Albassam4 Received: 4 May 2020 / Accepted: 17 July 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Nanocomposites (1−x)MnS‒xZnS (x = 0, 0.25, 0.5, 0.75, 1) heterostructures were synthesized by a simple chemical procedure at low temperature (300 °C). The influence of the alloying ratio (x) on the phases developed was investigated utilizing the Rietveld X-ray diffraction (XRD) analysis and Fourier transform infrared (FTIR). Zinc sulfide crystallized in one phase having zincblende structure, while manganese sulfide was formed in three phases having cubic and hexagonal structures. The determined crystallite size for ZnS was in the range 3–4 nm, resembling quantum dots, while for the cubic MnS phase the size was bigger in the range 15–20 nm, and it is much bigger for MnS hexagonal phase, about 76 nm. A High-resolution transmission electron microscope (HRTEM) images confirmed the big difference in particle sizes of MnS and ZnS. The UV diffused reflectance was obviously affected by the ratio of MnS to ZnS in the matrix; the intermediate composites (0.25, 0.5, and 0.75) had bandgap energy less than those of pure MnS and ZnS. The refractive index value was influenced by the degree of crystallinity and density of the samples. Photoluminescence (PL) analysis revealed high dependence on the sample composition with ZnS and the intermediate composites samples had broader spectra compared to the MnS sample; the intermediate samples were blue shifted. Also, PL intensities of intermediate nanocomposites were less than those of MnS and ZnS samples.
1 Introduction Semiconductor nanomaterials doped with Mn ions have been widely studied due to their optical characteristics which nominate it to be used in several optoelectronic and bio-imaging applications [1]. MnS is a wide bandgap (3.2 eV) semiconductor material which has exchange-coupling between Mn–Mn pairs [2]. Manganese sulfide usually * Zein K. Heiba [email protected] * Mohamed Bakr Mohamed [email protected] 1
Physics Department, Faculty of Science, Ain Shams University, Cairo, Egypt
2
Physics Department, Faculty of Science, Taibah University, Al‑Madina al Munawarah, Saudi Arabia
3
Physics Department, Faculty of Science, Taif University, Taif 21974, Saudi Arabia
4
Research Chair of Exploitation of Renewable Energy Applications in Saudi Arabia, Physics and Astronomy Department, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia
exists as M nS2 (cubic), β-MnS (zinc blende), γ-MnS (wurtzite), and α-MnS (rock salt) polymorphs [3, 4]. Meanwhile, zinc sulfide (ZnS) has also a large direct bandgap around 3.8 eV, a small exciton Bohr radius of 2.5 nm with a large exciton binding energy (40 meV), and a high refractive index (n = 2.57) [5, 6]. Therefore, it can be used in different applications such as ultraviolet light-emi
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