Vacancy-Defect-Regulated Two-Dimensional Transition-Metal Dichalcogenides for Broadband Spectrum Photodetection

To take full use of the outstanding photoelectric properties of two-dimensional transition-metal dichalcogenides (2D TMDs), techniques for tuning their band gaps have been developed, among which defect engineering is found to be an effective way for broadband spectrum photodetection. Methods like pulsed laser deposition, thermal annealing, electron/proton beam etching, etc., can effectively reduce band gaps by introducing vacancy defects into TMDs, but they face the problems of high costs, uneven distribution of prepared defects, and unstable material properties. To solve these problems, we proposed a two-step strategy from "alloy synthesis" to "vacancy introduction". Taking use of the bond energy differences between W–Se and W–Te in ternary alloy, WSe2(1–x)Te2x samples with homogeneous distributions of Se and Te were first synthesized, and then vacancy defects could be introduced through controllable release of Te atoms during a hydrogen-assisted annealing process, resulting in ∼4.1% vacancy defects with uniform distribution. A 910 nm photoluminescence (PL) peak appears in the annealed WSe2(1–x)Te2x, exhibiting a 110 nm red shift from the 800 nm peak of the unannealed alloy. Photoresponse of up to 1000 nm of the corresponding device verifies that a broadband spectrum detection TMD device has been successfully achieved in this study.