Liquid-Alloy-Assisted Growth of 2D Ternary Ga 2 In 4 S 9 toward High-Performance UV Photodetection.

2D ternary systems provide another degree of freedom of tuning physical properties through stoichiometry variation. However, the controllable growth of 2D ternary materials remains a huge challenge that hinders their practical applications. Here, for the first time, by using a gallium/indium liquid alloy as the precursor, the synthesis of high-quality 2D ternary Ga2 In4 S9 flakes of only a few atomic layers thick (≈2.4 nm for the thinnest samples) through chemical vapor deposition is realized. Their UV-light-sensing applications are explored systematically. Photodetectors based on the Ga2 In4 S9 flakes display outstanding UV detection ability (R λ = 111.9 A W-1 , external quantum efficiency = 3.85 × 104 %, and D* = 2.25 × 1011 Jones@360 nm) with a fast response speed (τring ≈ 40 ms and τdecay ≈ 50 ms). In addition, Ga2 In4 S9 -based phototransistors exhibit a responsivity of ≈104 A W-1 @360 nm above the critical back-gate bias of ≈0 V. The use of the liquid alloy for synthesizing ultrathin 2D Ga2 In4 S9 nanostructures may offer great opportunities for designing novel 2D optoelectronic materials to achieve optimal device performance.