Synthesis of Transition Metal Disulfides with Liquid Ammonium Sulfide as a Reliable Sulfur Precursor

We introduce liquid ammonium sulfide as a reliable and carbon-free sulfur precursor for synthesizing large-area transition metal disulfides (TMdS) in chemical vapor deposition.The flux of sulfur during TMdS growth is precisely controlled by passing a known amount of carrier gas through a bubbling system containing liquid ammonium sulfide.However, controlling the flux of sulfur through the conventional evaporation of sulfur powder using a heating belt remains a challenge.By achieving controllability of sulfur flux, we study growth kinetics such as nucleation density and growth rate.Furthermore, the continuous supply of the sulfur precursor results in the growth of a large-area monolayer and a few layers of MoS 2 film.In addition, we present the feasibility of ammonium sulfide as an effective and clean precursor for the growth of a wide range of TMdS, thus enabling it to serve as a universal sulfur precursor.