Synthesis of heptanary monolayer medium-entropy alloy via chemical vapor deposition for high-performance infrared photodetectors

Entropy engineering has emerged as a promising paradigm for tailoring the electronic and photoelectric properties of materials. Although high-entropy transition metal sulfides have been achieved, entropy engineering in two-dimensional (2D) tellurides remains challenging. In this work, we report the successful synthesis of a 1T' monolayer heptanary medium-entropy (ME) alloy (Mo_aW_bFe_cCo_dS_xSe_yTe_z) via a one-step chemical vapor deposition method. Advanced characterizations, including scanning transmission electron microscopy, energy dispersive X-ray spectroscopy, and electron energy loss spectroscopy confirm the uniform atomic-level distribution of the seven constituent elements within the alloy. The 1T' ME alloy device exhibits a high drain current of ~ 6.5 mA, which is 216 times higher than the ~ 30 μA observed in pristine 1T' MoTe₂. Furthermore, the 1T' ME alloy photodetector exhibits responsivities of 27.92 A/W at 1064 nm and 63.74 A/W at 1550 nm, outperforming those of the pristine 1T' MoTe₂ by more than two orders of magnitude. This remarkable enhancement is attributed to the reduced Schottky barrier (15.9 meV) at the 1T' ME alloy/electrode interface, along with the enhanced conductance (0.43 S) and reduced thermal activation energy (4.1 meV) in the 1T' ME alloy, collectively facilitating more efficient carrier injection and transport. Our work provides a distinct pathway for tailoring the properties of transition metal dichalcogenides through entropy engineering and offers valuable insights for the design of high-performance infrared photodetectors.