Quantum Multibody Interactions in Halide-Assisted Vapor-Synthesized Monolayer WSe₂ and Its Integration in a High Responsivity Photodetector with Low-Interface Trap Density

Among the two-dimensional (2D) transitional-metal dichalcogenides, monolayer (1L) tungsten diselenide (WSe 2 ) has recently attracted a great deal of interest because of its direct band gap and tunable charge transport behavior, making it attractive for a variety of electronic and optoelectronic applications. Controlled and efficient synthesis of 1L WSe 2 using chemical vapor deposition (CVD) is often challenging because of the high temperatures required to generate a steady flux of tungsten atoms in the vapor phase from the oxide precursors. Here, the use of halide-assisted low-pressure CVD with NaCl helps to reduce the growth temperature to ∼750 °C, which is lower than the typical temperatures needed with conventional CVD for realizing 1L WSe 2 . Moreover, we experimentally probed the quantum multibody interactions in 1L WSe 2 ascribed to excitons, trions, and other localized states by analyzing the temperature-dependent photoluminescence spectra, where such multibody interactions govern the intrinsic electronic and optoelectronic properties of 1L WSe 2 for device platforms. The role of the metal–2D semiconductor interface is also critical to realize high-performance devices. In this study, a 1L WSe 2 -based photodetector was fabricated using Al contacts, which shows a high photoresponsivity, and the interface-state density D it of the Al/WSe 2 junction was computed to be the lowest reported to date ∼3.45 × 10 12 cm –2 eV –1 . Our work demonstrates the tremendous potential of WSe 2 to open avenues for state-of-the-art electronic, optoelectronic, and quantum-optoelectronic devices using scalable synthesis routes.