Controlled growth, characterization and field emission properties of high-quality WS2 nanowires by chemical vapor deposition

Abstract

The controlled synthesis of high-quality WS2 nanowires exhibiting good physical and chemical properties is urgent and remains challenging. In this work, the WS2 nanowires are deposited on SiO2/Si substrates by chemical vapor deposition method using sulfides and halides with transition metal oxides as precursors. The effects of various experimental parameters, such as reaction temperature, Ar gas flow rate, holding time and substrate position, on the growth of WS2 nanowires are investigated. The detailed structural analyses indicate that the deposited WS2 nanowires with high crystalline quality possess the hexagonal 2H phase structure, and exhibit a smooth surface, uniform size and density distribution with a diameter of about 200 nm. Raman spectrum exhibits empirical characteristic peaks of in-plane vibration E12g(Г) and out-of-plane vibration A1g(Г) for the deposited WS2 nanowires. The formation mechanism of deposited 2H-WS2 nanowires is due to the preferential formation of WO3 nanowires during the reaction process, which is caused by further vulcanization to form the 2H-WS2 nanowires. Field emission property measurements are carried out based on the deposited WS2 nanowires, showing good turn-on field Eto of 2.4 V and threshold field Ethr of 6.8 V as well as excellent stability, which are attributed to their unique geometrical features.