A Thrifty Liquid-Phase Exfoliation (LPE) of MoSe₂ and WSe₂ Nanosheets as Channel Materials for FET Application

Two-dimensional materials are trending nowadays because of their atomic thickness, layer-dependent properties, and their fascinating application in the semiconducting industry. In this work, we have synthesized MoSe₂ and WSe₂ nanosheets (NSs) via a liquid-phase exfoliation method and investigated these NSs as channel materials in field-effect transistors (FET). The x-ray diffraction (XRD) pattern revealed that the synthesized NSs have a 2H phase with 0.65 nm d-spacing which belongs to the (002) Miller plane. Transmission electron microscopy (TEM) studies revealed that MoSe₂ and WSe₂ have a nanosheet-like structure, and the average lateral dimensions of these NSs are ~ 25 nm and ~ 63 nm, respectively. From Raman spectra, we found that the intensity of the A_1g vibrational mode decreases with the reduction in the number of layers. UV-visible spectroscopy revealed that the bandgap values of MoSe₂ and WSe₂ NSs are 1.55 eV and 1.50 eV, respectively, calculated using the Tauc equation. The output and transfer characteristics of the FET devices reveals that the fabricated FETs have good ohmic contact with the channel material and an ON/OFF current ratio of about 10² for both devices. This approach for the fabrication of FET devices can be achieved even without sophisticated fabrication facilities, and they can be applied as gas sensors and phototransistors, among other applications.