Two-dimensional (2D) transition metal dichalcogenides (TMDs) exhibit an intriguing array of layer-, topology-, and morphology-dependent properties, and have demonstrated enormous potential in optoelectronics, energy conversion, and quantum information science. Although “top-down” approaches can be used to define crystal morphologies and dimensions, explicit synthetic control of the physical properties of TMD crystals is desirable, but also a major challenge. We demonstrate a gas-phase synthesis method that significantly transforms the morphology and dimensionality of MoS2 and other TMD crystals without lithography. Synthesis of MoS2 on Si (001) surfaces pre-treated with phosphine (PH3) furnishes high aspect ratio nanoribbons of crystalline 2H phase MoS2. The widths of these nominally 1D crystals are exceptionally uniform and their edges are sharper than those of TMD crystals prepared by most other means. Notably, the widths of the MoS2 nanoribbons can be systematically controlled between 30 nm and 500 nm by varying the concentration of PH3 gas introduced during the Si surface treatment step. Detailed kinetic studies supported by cluster expansion and DFT calculations indicate that the structure and concentration of the underlying Si–phosphide surface moieties is instrumental in transforming growth of MoS2 from a conventional 2D triangular to nominally 1D morphology. Notably, far-field and near-field photoluminescence (PL) studies of 1D MoS2 crystals show that they exhibit an emission peak which is blue-shifted by 50 meV relative to that of 2D MoS2 nanocrystals. Our efforts highlight future opportunities for development of designer substrates that could mediate the synthesis of new low-dimensional crystals with prescribed structures and properties.

Tuning the dimensionality and properties of TMD crystals through substrate directed synthesis

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.