Self-Oriented MoS2 Nanosheets on Microcrystalline Diamond Layers: Controlled Synthesis and Optoelectronic Effects

Combining diamond and two-dimensional materials is attracting increasing attention for synergic effects that have the best of both worlds. Applications range from electronics and quantum technologies to catalysis, energy conversion, and biosensors. Here, heterostructures based on hydrogenated diamond microcrystalline thin films with attached MoS₂ nanosheets are formed by a single-zone annealing at atmospheric pressure. By varying the process parameters, MoS₂ sheets are controllably synthesized in a vertical or horizontal orientation with respect to the diamond grain facets, which leads to a pronounced impact on the electronic and optoelectronic properties of the heterostructures. Raman, SEM, AFM, KPFM, and SKP analyses show the influence of the MoS₂ orientation and thickness on the work function, surface potential, spatially and spectrally resolved photovoltage, and charge transfer kinetics. The aligned growth of MoS₂ nanosheets and their properties are elucidated by molecular mechanics and time-dependent DFT calculations, which explain the mechanism of the assembly and the related optoelectronic effects in a straightforward way. The major switching point occurs precisely at 11 nm of the MoS₂ thickness/length. The highest photoresponse of 350 meV and favorable charge transfer are observed for the vertical MoS₂ arrangement on diamond, yet without a covalent bond. The results and theoretical model hint at broader implications beyond the MoS₂-diamond system.