Synthesis and characterization of tungsten diselenide thin films by the two-step method

Fabrication of thin films of WSe2 is challenging and various methods are being explored. This study investigates the thermoelectric properties of tungsten diselenide thin films. The thin films are fabricated on Si substrates by using two-step processes. Here, the selenization of DC sputtered W thin films was carried out at different temperatures in the range of 400 to 500oC in the steps of 50oC. The crystal structure is found to be hexagonal and crystallite sizes increase with the selenization temperature. The morphology of the thin films selenized at 400oC shows no separated particles while raising the selenization temperature from 450oC to 500 °C uniform distribution of particles is observed. The shape of the particles was found spherical and rod-like. The Raman spectra show four modes: E1g,\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\:{\text{E}}_{2\text{g}}^{1}$$\end{document}, A1g, and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\:{\text{B}}_{2\text{g}}^{1}$$\end{document}. Here, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\:{\text{B}}_{2\text{g}}^{1}$$\end{document} is associated with the interlayer interaction. The electrical resistivities of these thin films exhibit the conduction mechanism of the band conduction model. The highest Seebeck coefficient was reported for S500 (-9.15µV/K). Also, the power factor of S500 is the highest i.e. 13.4 Χ 10− 5µW/mK2 This study shows the potential use of the selenization process to fabricate the WSe2 thin films and optimize temperature for better thermoelectric properties.