Controllable synthesis of WS2(1-x)Se2x monolayers with fast photoresponse by a facile chemical vapor deposition strategy

Abstract

Two-dimensional transition metal dichalcogenides (TMDs) alloys such as WS Se have attracted much interest in the fundamental science and device fabrication for their composition-tunable chemical and physical properties. However, the traditional chemical vapor deposition (CVD) methods often rely on precursors with high melting point such as WO , WS and WSe . Here, we report a facile CVD strategy for the formation of high quality WS Se monolayers with composition-tunable optical and electronic properties by using highly evaporated sodium tungstate dihydrate (Na WO ·2H O) precursor as W source. The as-grown samples exhibit uniform allocation of W, S, and Se elements across the domain and the Se (or S) composition can be continually modulated from 0 to 2. The band gap evolves continuously from 1.97 eV for WS to intermediate value for WS Se and then to 1.63 eV for WSe . Electrical transport studies further reveal the transition from n-type for WS to bipolar (or slightly n-type) for WS Se and then to p-type for WSe . Furthermore, the as-grown WS Se -photodetectors exhibit good photo response to visible light (532 nm) with a fast response time of about 20 ms. Our facile and precise synthesis strategy can be used as a general route to fabricating such composition modulated 2D TMD alloys for optoelectronic applications. 2(1-x) 2x 3 2 2 2(1-x) 2x 2 4 2 2 2(1-x) 2x 2 2 2(1-x) 2x 2 2(1-x) 2x