Investigation of Morphological, Optical, and Dielectric Properties of RF Sputtered WOx Thin Films for Optoelectronic Applications

Samiya Mahjabin; Md Mahfuzul Haque; K Sobayel; Vidhya Selvanathan; M S Jamal; M S Bashar; Munira Sultana; Mohammad Ismail Hossain; Md Shahiduzzaman; Merfat Algethami; Sami S Alharthi; Nowshad Amin; Kamaruzzaman Sopian; Md Akhtaruzzaman

doi:10.3390/nano12193467

Investigation of Morphological, Optical, and Dielectric Properties of RF Sputtered WO_x Thin Films for Optoelectronic Applications

Nanomaterials (Basel). 2022 Oct 4;12(19):3467. doi: 10.3390/nano12193467.

Authors

Affiliations

¹ Solar Energy Research Institute (SERI), Universiti Kebangsaan Malaysia (The National University of Malaysia), Bangi 43600, Malaysia.
² Bangladesh Council of Scientific and Industrial Research, Dhaka 1205, Bangladesh.
³ Department of Electrical and Computer Engineering, University of California, Davis, CA 95616, USA.
⁴ Nanomaterials Research Institute (NanoMaRi), Kanazawa University, Kakuma, Kanazawa 920-1192, Japan.
⁵ Department of Physics, Faculty of Science, Taif University, P.O. Box 11099, Taif 21944, Saudi Arabia.
⁶ Institute of Sustainable Energy, Universiti Tenaga Nasional (The National Energy University), Jalan IKRAM-UNITEN, Kajang 43000, Malaysia.
⁷ Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8573, Ibaraki, Japan.

Abstract

Tungsten oxide (WO_x) thin films were synthesized through the RF magnetron sputtering method by varying the sputtering power from 30 W to 80 W. Different investigations have been conducted to evaluate the variation in different morphological, optical, and dielectric properties with the sputtering power and prove the possibility of using WO_x in optoelectronic applications. An Energy Dispersive X-ray (EDX), stylus profilometer, and atomic force microscope (AFM) have been used to investigate the dependency of morphological properties on sputtering power. Transmittance, absorbance, and reflectance of the films, investigated by Ultraviolet-Visible (UV-Vis) spectroscopy, have allowed for further determination of some necessary parameters, such as absorption coefficient, penetration depth, optical band energy gap, refractive index, extinction coefficient, dielectric parameters, a few types of loss parameters, etc. Variations in these parameters with the incident light spectrum have been closely analyzed. Some important parameters such as transmittance (above 80%), optical band energy gap (~3.7 eV), and refractive index (~2) ensure that as-grown WO_x films can be used in some optoelectronic applications, mainly in photovoltaic research. Furthermore, strong dependencies of all evaluated parameters on the sputtering power were found, which are to be of great use for developing the films with the required properties.

Keywords: RF magnetron sputtering; electron transport layer; metal oxide; optoelectronics; perovskite solar cell; photovoltaic; sputtering; tungsten oxide.

Grants and funding

This work was supported by the Bangabandhu Fellowship Trust (BBFT), Bangladesh, Universiti Kebangsaan Malaysia, Malaysia through the Long-term Research Grant Scheme (LRGS/1/2019/UKM-UKM/6/1) and Taif University Researchers Supporting Project Number (TURSP-2020/248), Taif University, Taif, Saudi Arabia.