High mobility solution processed MoS2 thin film transistors

Abstract

A simple wet-chemical synthesis of layered MoS2 thin films on sapphire is reported. The gap in understanding solution processed MoS2 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 MoS2 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 MoS2 grain size. For charge transport analysis, top-gate top-contact thin film transistors (TFTs) based on these solution processed MoS2 films were fabricated. Ionic liquid gating of the TFT devices exhibited n-type semiconducting behaviour with field-effect mobility as high as 12.07 cm2/Vs and Ion/off ratio ∼ 106. 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.