Controllable synthesis of molybdenum tungsten disulfide alloy for vertically composition-controlled multilayer

The effective synthesis of two-dimensional transition metal dichalcogenides alloy is essential for successful application in electronic and optical devices based on a tunable band gap. Here we show a synthesis process for Mo(1−x)W(x)S(2) alloy using sulfurization of super-cycle atomic layer deposition Mo(1−x)W(x)O(y). Various spectroscopic and microscopic results indicate that the synthesized Mo(1−x)W(x)S(2) alloys have complete mixing of Mo and W atoms and tunable band gap by systematically controlled composition and layer number. Based on this, we synthesize a vertically composition-controlled (VCC) Mo(1−x)W(x)S(2) multilayer using five continuous super-cycles with different cycle ratios for each super-cycle. Angle-resolved X-ray photoemission spectroscopy, Raman and ultraviolet–visible spectrophotometer results reveal that a VCC Mo(1−x)W(x)S(2) multilayer has different vertical composition and broadband light absorption with strong interlayer coupling within a VCC Mo(1−x)W(x)S(2) multilayer. Further, we demonstrate that a VCC Mo(1−x)W(x)S(2) multilayer photodetector generates three to four times greater photocurrent than MoS(2)- and WS(2)-based devices, owing to the broadband light absorption.