Large-Scale Multilayer MoS2 Nanosheets Grown by Atomic Layer Deposition for Sensitive Photodetectors

Two-dimensional (2D) transition-metal dichalcogenides have promising optoelectronic applications. However, most reported MoS2-based photodetectors are based on MoS2 flakes, dozens of microns in size, prepared by mechanical exfoliation or chemical vapor deposition, which limits their practical applications. In this study, a wafer-scale, continuous, and uniform multilayer MoS2 nanosheet was grown on an insulating single-crystal sapphire substrate by atomic layer deposition (ALD), with MoCl5 and hexamethyldisilathiane as precursors, because of the smaller lattice mismatch between crystalline sapphire and hexagonally arranged MoS2 compared with polycrystalline substrates. Then, large-area MoS2 nanosheets with high uniformity and homogeneity were obtained on Al2O3/Si and SiO2/Si substrates via large-scale peeling and vacuum stacking transfer. Subsequently, MoS2 photodetectors were fabricated on both substrates with ALD-MoS2 as a photosensitive channel material and high-k Al2O3 or SiO2 as a dielectric layer, which resulted in gate control with relatively low and high voltages, respectively. A high photoresponsivity (R) of 577.4 A W–1 was achieved for the MoS2 photodetector fabricated on the Al2O3/Si substrate at an illumination power density (Pin) of 5.01 μW cm–2 (λ = 500 nm). In addition, the MoS2 photodetectors exhibited a light response over a wide wavelength range (400–700 nm). Moreover, a MoS2 photodetector array containing 4 × 3 photodetectors with a uniform photoelectric response was demonstrated. These results will facilitate future applications of 2D materials in large-scale, high-performance photoelectronic devices and circuits.