Selectable Synthesis of 2-D MoS2and Its Electronic Devices: From Isolated Triangular Islands to Large-Area Continuous Thin Film

Abstract

We report on the controllable and selectable synthesis of two-dimensional (2-D) molybdenum disulfide (MoS2 ) by molybdenum trioxide sulfurization with chemical vapor deposition. By controlling the sulfurization timing and substrates positions, the selectable growth of MoS2 isolated triangular islands and continuous thin film was successfully performed independently with the same home-built furnace setup. Also, we found that the hydrofluoric acid substrate treatment took effects on MoS2 nucleation seed densities and modulated the sizes of the triangular islands. Atomic force microscopy and Raman and photoluminescence spectroscopy were used to characterize and compare the properties of MoS2 triangular islands and continuous thin film. The MoS2 triangular islands were monolayers and highly crystalline in nature; where the continuous thin film was formed by small grain size MoS2 nanosheets with smooth surface morphology and a large covered area of up to centimeters. Back-gated field effect transistors (FETs) of as-grown MoS2 triangular islands and continuous thin film were fabricated to analyze their electrical properties. The electron mobilities were measured to be 11.42 and 4.04 cm2/V·s respectively, and with an excellent on/off current ratio up to over 10 8, which demonstrated the good quality of the as-grown MoS2 samples. Furthermore, both the MoS2 triangular islands and continuous thin film FETs exhibited a near ideal current saturation characteristic, which shows the real potential of future applications for 2-D electronic devices.