Structural, morphological, and optical bandgap properties of ZnS thin films: a case study on thickness dependence

• Published in: Optical and quantum electronics Vol. 56; no. 7
• Main Authors: Grayeli, Alireza, Sadeghi, Mohammad, Shakoury, Reza, Matos, Robert Saraiva, da Fonseca Filho, Henrique Duarte, Arman, Ali
• Format: Journal Article
• Language: English
• Published: New York Springer US 02.06.2024; Springer Nature B.V
• Subjects: Absorption spectroscopy; AFM; Bandgap properties; Blue shift; Case-studies; Characterization and Evaluation of Materials; Computer Communication Networks; Crystallite size; Crystallites; Electrical Engineering; Electron diffraction; Elongated structure; Energy gap; Film thickness; Fractals; Glass substrates; II-VI semiconductors; Infrared devices; Infrared spectra; Lasers; Magnetic properties; Magnetron sputtering; Morphology; Multi fractals; Multifractal; Nanocrystals; Near infrared radiation; Optical Devices; Optical properties; Optical-bandgap; Optics; Percolation; Photonics; Physics; Physics and Astronomy; Solvents; Sputtering; Structural analysis; Temperature dependence; Thin films; Topography; X ray diffraction; X- ray diffractions; XRD; Zinc sulfide; Zinc sulfide thin films; Zinc sulfide; AFM; XRD; Optical properties; Sputtering; Multifractal
• ISSN: 1572-817X; 0306-8919; 1572-817X
• DOI: 10.1007/s11082-024-07039-6

Thin films of zinc sulfide (ZnS) with varying thicknesses have been successfully fabricated using radio frequency magnetron sputtering on glass substrates at a temperature of 300 K. Structural analysis via X-ray diffraction and selected area electron diffraction confirmed the presence of nanocrystalline cubic ZnS phases in the films. The crystallite size, determined from X-ray diffraction lines, ranged between 42 and 55 nm. We also explored the morphological attributes of these surfaces and observed significant changes in both grain shape and size. Our atomic force microscopy analyses revealed that the thinner film displayed a topography marked by thinner, elongated rough peaks. As the film thickness increased, these rough peaks gradually transformed into wider, flatter features. Additionally, the films exhibited distinct percolation properties, which were undeniably tied to the alterations in the shape and size of the ZnS grains on their surfaces. Thinner samples demonstrated more pronounced surface percolation (FS > 0.5) compared to thicker samples, which displayed reduced surface percolation. Furthermore, we noted that the 250 nm film predominantly showcased strongly multifractal 3D spatial patterns in contrast to the other films. Spectroscopic measurements in the UV–visible-near infrared region revealed high transparency across the 350–850 nm spectra, with a noticeable blue shift in the absorption edge. Calculations yielded direct allowed band gaps within the range of 3.69–3.85 eV. These results indicate that the optical properties of films can be tailored by their structural and morphological characteristics, thereby offering valuable guidance for their appropriate applications.