Two-dimensional tungsten disulfide nanosheets and their application in self-powered photodetectors with ultra-high sensitivity and stability. (July 2022)

• Record Type: Journal Article
• Authors: Ortiz, Wilber; Malca, Carlos; Barrionuevo, Danilo; Aldalbahi, Ali; Pacheco, Elluz; Oli, Nischal; Feng, Peter
• Is Part Of: Vacuum. Volume 201(2022)
• Publication Date: 2022-07
• Subjects: 2D tungsten disulfide nanosheets -- Highly sensitive photodetector -- High-throughput photocurrent -- High optical absorption; Vacuum -- Periodicals; 621.55
• DOI: 10.1016/j.vacuum.2022.111092
• Languages: English
• ISSNs: 0042-207X

Abstract

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 ∼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 2 V, it exhibits a responsivity of 12.74 mA/W and a detectivity of 1.17 × 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. Highlights: 2D WS2 nanosheets deficient in S showed a higher photon absorption in the near-infrared range under zero bias. 2D WS2 nanosheets improved light absorption in a wide visible spectrum range. Nanosheets exhibited high sensitivity and enhanced photoresponse under the built-in electric field. Quantum confinement is the spatial confinement of electron-hole pairs in 2D WS2 nanosheets.