Liquid Phase Exfoliation and Characterization of Few Layer MoS2 and WS2 Nanosheets as Channel Material in Field Effect Transistor

Field effect transistors (FETs) are considered as the backbone of electronic industry. In this study, we adopted a simple drop cast method for the fabrication of MoS2 and WS2 channel based FET on commercially available pre-patterned OFET devices. The synthesis of few-layers thick MoS2 and WS2 nanosheets (NSs) has been done by solvent-assisted exfoliation method. FESEM and TEM study reveals that NSs have lateral dimensions in micron and have polycrystalline nature. From XPS, it is observed that MoS2 NSs has 2H phase whereas WS2 have hybrid 1T and 2H phase. The frequency difference in Raman vibrational mode for MoS2 and WS2 NSs is 24.08 cm(-1) and 63.84 cm(-1) respectively, confirms that number of layers is reduced after sonication. UV-visible spectroscopy reveals that the bandgap is 1.7 eV and 1.8 eV for MoS2 and WS2 NSs respectively. Later, these nanosheets have been drop-casted as the channel material on pre-patterned FETs devices and their output and transfer characteristics have been studied. It found that the current On/Off ratio is 10(4) and 10(3) for MoS2 and WS2-FET device respectively. This facile fabrication of FET devices may provide a new stage for researchers who do not have access of lithography facilities for FET fabrication.