Strong Band Bowing Effects and Distinctive Optoelectronic Properties of 2H and 1T ' Phase-Tunable Mo(x)Re(1-)(x)S(2)Alloys

Structure and energy band engineering of 2D materials via selective doping or phase modulation provide a significant opportunity to design them for optoelectronic devices. Here, the synthesis of high-quality Mo(x)Re(1-)(x)S(2)alloys with tunable composition and phase structure via chemical vapor deposition growth is reported, and their novel energy band structures and optoelectronic properties are explored. The phase separation and structure reconstruction, which are found to be two serious problems in the synthesis of these alloys, are successfully suppressed through tuning their growth thermodynamics. As a result, the obtained Mo(x)Re(1-)(x)S(2)alloys have uniform composition, phase structure, and crystal orientation. Together with X-ray photoelectron spectroscopy analysis and first-principle calculation, the Re/Mo doping-induced Fermi level up-shift/down-shift, new electronic states, and sub-gap formation in Mo(x)Re(1-)(x)S(2)alloys are revealed. Especially, a strong band bowing effect is discovered in the Mo(x)Re(1-)(x)S(2)alloys with structure transition between 1T ' and 2H phases. Furthermore, these alloys reveal tunable conduction behavior from n-type to bipolar and p-type in 1T ' phase, as well as novel bipolar-like electron conduction behavior in 2H alloys. The results highlight the unique alloying effects, which do not exist in the single-phase 2D alloys, and provide the feasibility for potential applications in building novel electronic and optoelectronic devices.