Unmet NeedTwo-dimensional (2D) transition-metal dichalcogenide (TMD) crystals are a versatile platform for optoelectronic, catalytic, and quantum device studies. These crystals are useful for their tunable bandgap, surface and edge reactivity, layer dependent properties, and potential to create multi-layer architectures that incorporate atomically abrupt interfaces. The micro/nano-structure and dimensionality of a TMD crystal determine many of its physical properties, while the phase and orientation of the TMD crystal layers are frequently manipulated to tune its electronic band structure. Explicit manipulation of crystallite size, shape, phase, and layer number is a major challenge, despite existing vapor-phase growth methods and exfoliation strategies that offer access to layered materials, such as 2D-TMDs. Though the TMD crystal desired properties are dictated by crystallite micro/nanostructure and dimensionality, there is a lack of synthetic methods to controlling these attributes.
Technology OverviewThe Johns Hopkins researchers have demonstrated a gas-phase synthesis method to control the micro/nanostructure and dimensionality of 2D-TMD crystals. The synthesis method realizes directed growth of TMDs on phosphine-treated Si substrates to yield crystalline TMD nanoribbons with tunable widths. This method’s directed growth mode differs significantly from typical omni-directional growth modes for forming triangular 2D-TMD crystals on SiO
2 substrates. The cornerstone of this synthetic method involves the use of P atom functionalized Si surfaces, which directs the in-plane growth of TMD crystals during synthesis via a chemical vapor deposition (CVD) protocol. The researchers also developed a low-pressure CVD protocol for their TMD synthesis compatible with the P-functionalized Si surfaces. After the CVD and synthesis protocols, the crystals are confirmed using scanning election microscopy (SEM), Raman spectroscopy, and atomic force microscopy (AFM), detailing the majority of products created are 2D-TMD crystals. The 2D crystals created were consistent with 2D crystals produced through standard chemical vapor transport protocols previously reported.
Stage of DevelopmentThe inventors have completed methods involved in the creation of 2D-TMD crystals, and controlling their structure and dimensionality while being created. One method is involved with seeding the crystals for growth, while the other protocol is involved in synthesizing the attributes (size, shape, phase, and layer number) of the seeded crystals for specific use.
PublicationsChowdhury, T., Kim, J., Sadler, E.C. et al. Substrate-directed synthesis of MoS2 nanocrystals with tunable dimensionality and optical properties. Nat. Nanotechnol. 15, 29–34 (2020) doi:10.1038/s41565-019-0571-2
