Abstract
Two-dimensional (2D) tungsten disulfide nanosheets (WS2) could be a promising candidate for high-performance self-powered photodetectors. The present 2D nanosheets were obtained from liquid exfoliation in a mixture of ethanol, methanol, and isopropanol via a direct dispersion and ultrasonication method. Using the spin-coating technique, a thin film of uniform thickness was formed on the SiO2/Si substrate. Energy-dispersive X-ray analysis showed that the S/W ratio in the fabricated WS2 film was around 1.2 to 1.34, indicating certain deficiencies in the S atoms. These S vacancies induce localized states within the bandgap of pristine WS2, resulting in a higher conductivity in the exfoliated sample. The obtained thin film seems to be highly efficient in photoelectric conversion, with a responsivity of similar to 0.12 mA/W at 670 nm under zero bias voltage, with an intensity of 5.2 mW/ cm(2). Instead, at a bias of 2V, it exhibits a responsivity of 12.74 mA/W and a detectivity of 1.17 x 10(10) cm Hz(1/2) W-1 at 4.1 mW/cm(2). The present 2D nanosheets exhibit high photon absorption in a wide range of spectra from the near-infrared (IR) to near UV spectrum.