≈190 nm Broadband Tunable Graded‐Composition MoS _2(1–x) Te _2x Alloys via Cooling‐Gradient Growth

Abstract 2D transition metal dichalcogenides (TMDs) are promising candidates for tunable optoelectronic applications. Among them, compositionally graded TMD alloys offer a unique platform for spatial engineering of optical properties. However, prior demonstrations are constrained by limited bandgap modulation ranges (1.95–1.70 eV, representing a wavelength modulation range of ≈90 nm), hindering their integration into broadband photonic devices. Here, this study reports a cooling temperature gradient‐assisted chemical vapor deposition (CVD) strategy for synthesizing monolayer MoS 2(1–x) Te 2x alloys with continuously graded compositions. By precisely tailoring the thermal environment, a quasi‐equilibrium Te‐for‐S substitution is achieved, yielding smooth compositional transitions across the monolayer. This enables exceptional photoluminescence tunability from 670 nm (MoS 2 ‐rich) to 860 nm (MoTe 2 ‐rich), representing a substantial ≈190 nm modulation range, far surpassing previous TMD alloy systems.Furthermore, self‐powered photodetectors based on the graded monolayers demonstrate robust photoresponse under 808 nm near‐infrared illumination, benefiting from enhanced light absorption and carrier separation in Te‐rich regions. This work not only overcomes the tunability bottleneck in 2D alloy systems, but also provides a scalable pathway toward high‐performance, wavelength‐adaptive optoelectronic devices with spatially programmable functionalities.