High mobility solution processed MoS2 thin film transistors

Abstract A simple wet-chemical synthesis of layered MoS 2 thin films on sapphire is reported. The gap in understanding solution processed MoS 2 deposition needs to be closed to exploit all its excellent properties for low-cost applications. In this work, as deposited Mo-precursor thin films were prepared based on the solubility and coating properties of Molybdenum(V) chloride in 1-Methoxy-2-propanol. Subsequent annealing of the deposited amorphous Mo-precursor films in the presence of sulfur resulted in the formation of highly crystalline layered MoS 2 films on sapphire. Improved crystallinity of the deposited films was achieved by increasing the process temperature and performing the post-annealing treatment. Post-annealing at temperatures above 900 °C increased the uniformity of multilayer films, together with the increase of MoS 2 grain size. For charge transport analysis, top-gate top-contact thin film transistors (TFTs) based on these solution processed MoS 2 films were fabricated. Ionic liquid gating of the TFT devices exhibited n -type semiconducting behaviour with field-effect mobility as high as 12.07 cm 2 /Vs and I on/off ratio ∼ 10 6 . X-ray photoelectron spectroscopy measurements revealed that the films annealed between 900 °C and 980 °C had an average chemical composition of S/Mo ∼ 1.84. This facile liquid phase synthesis method with centimeter-scale uniformity and controllable film thickness up to 1.2 ± 0.65 nm is suitable for low-cost preparation of other transition metal dichalcogenides thin films in next-generation electronics.