Optical response of green synthesized thin Cr2O3 films prepared via drop and spin coatings

Tsegay, M.G.; Gebretinsae, H.G.; Welegergs, G.G.; Azizi, Sh.; Seopela, M.P.; Henini, M.; Maaza, M.; Nuru, Z.Y.

Abstract

This study investigated the impact of optical bandgap energy on the optical constants of Cr2O3 thin films, which were prepared via green synthesis method and deposited using drop and spin-coatings at 600, 800, 1000, and 1200 rpm onto Cu substrates. The deposited Cr2O3 thin films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), and UV–VIS-NIR spectroscopy. XRD revealed that the prepared nanocoating surfaces are pure eskolaite Cr2O3 phase. The grain size of the prepared Cr2O3 films decreased from 15 nm to 12 nm for the drop and spin coatings, respectively. The morphology of the drop and spin coated samples showed nanorods, mesospherical, and quasi-spherical shaped nanoparticles, respectively, along with the presence of O and Cr. The bandgap energy increased from 2.35 eV to 2.50 eV, with increasing Spin Coater rotational speeds (RS) from drop to 1200 rpm, respectively. As bandgap energy increase, the carriers' spatial dimension shrinks, resulting in grains smaller than or equal to the exciton's Bohr radius. Thicker film materials tend to have lower bandgap energies due to strain effects, whereas smaller grain sizes tend to have higher bandgap energies. The determined refractive index and extinction coefficient values vary as the bandgap energy varies for all prepared samples. These findings confirmed that differences in bandgap energy affect the refractive index (n) and extinction coefficient (k) of Cr2O3 thin films. These are attributed to quantum confinement, internal scattering, and interference effects of Cr2O3 thin film surfaces.

Citation

Tsegay, M., Gebretinsae, H., Welegergs, G., Azizi, S., Seopela, M., Henini, M., …Nuru, Z. (2023). Optical response of green synthesized thin Cr2O3 films prepared via drop and spin coatings. Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2023.06.225

• Journal Article Type: Article
• Acceptance Date: Jul 6, 2023
• Online Publication Date: Jul 8, 2023
• Publication Date: Jul 8, 2023
• Deposit Date: Dec 9, 2023
• Publicly Available Date: Jul 9, 2025
• Journal: Materials Today: Proceedings
• Electronic ISSN: 2214-7853
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• DOI: https://doi.org/10.1016/j.matpr.2023.06.225
• Keywords: Green Synthesis, Cr2O3 thin films, Optical Constants, Bandgap Energy, Optical properties
• Public URL: https://nottingham-repository.worktribe.com/output/28258465
• Publisher URL: https://www.sciencedirect.com/science/article/abs/pii/S2214785323036209?via%3Dihub
• Additional Information: This article is maintained by: Elsevier; Article Title: Optical response of green synthesized thin Cr2O3 films prepared via drop and spin coatings; Journal Title: Materials Today: Proceedings; CrossRef DOI link to publisher maintained version: https://doi.org/10.1016/j.matpr.2023.06.225; Content Type: article; Copyright: Copyright © 2023 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the 8th International Conference on Nanoscience and Nanotechnology in Africa.