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

Abstract

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 500^oC in the steps of 50^oC. The crystal structure is found to be hexagonal and crystallite sizes increase with the selenization temperature. The morphology of the thin films selenized at 400^oC shows no separated particles while raising the selenization temperature from 450^oC 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: E_1g,\(\:{\text{E}}_{2\text{g}}^{1}\)_, A_1g, and \(\:{\text{B}}_{2\text{g}}^{1}\). Here, \(\:{\text{B}}_{2\text{g}}^{1}\) 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.