Colloidal 2D Mo 1- x W x S 2 nanosheets: an atomic- to ensemble-level spectroscopic study

• Published in: Physical chemistry chemical physics : PCCP 2024-05, Vol.26 (17), p.13271-13278
• Main Authors: Fröhlich, Markus, Kögel, Marco, Hiller, Jonas, Kahlmeyer, Leo, Meixner, Alfred J, Scheele, Marcus, Meyer, Jannik C, Lauth, Jannika
• Format: Article
• Language: English
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/D4CP00530A

Composition dependent tuning of electronic and optical properties in semiconducting two-dimensional (2D) transition metal dichalcogenide (TMDC) alloys is promising for tailoring the materials for optoelectronics. Here, we report a solution-based synthesis suitable to obtain predominantly monolayered 2D semiconducting Mo W S nanosheets (NSs) with controlled composition as substrate-free colloidal inks. Atomic-level structural analysis by high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM) coupled with energy dispersive X-ray spectroscopy (EDXS) depicts the distribution of individual atoms within the Mo W S NSs and reveals the tendency for domain formation, especially at low molar tungsten fractions. These domains cause a broadening in the associated ensemble-level Raman spectra, confirming the extrapolation of the structural information from the microscopic scale to the properties of the entire sample. A characterization of the Mo W S NSs by steady-state optical spectroscopy shows that a band gap tuning in the range of 1.89-2.02 eV (614-655 nm) and a spin-orbit coupling-related exciton splitting of 0.16-0.38 eV can be achieved, which renders colloidal methods viable for upscaling low cost synthetic approaches toward application-taylored colloidal TMDCs.