Opportunities for high-throughput discovery in the synthesis and characterization of 2D monolayers, moiré materials, and synthetic van der Waals solids*

Atomically thin two-dimensional (2D) materials such as the transition metal dichalcogenides (TMDs) exhibit properties which are tunable via composition and interfacial coupling. Moreover, van der Waals heterostructures (vdWHS) assembled from 2D materials yield new properties, e.g., tunable moiré excitonic landscapes and sliding ferroelectricity. There is still a pressing need to understand the synthesis and properties of 2D monolayers and vdWHS – and one key bottleneck is the limited throughput of synthesis and characterization. Here, I will highlight three recent advances and opportunities for computational and experimental synergy:

 

(1.) We developed hybrid MOCVD (HyMOCVD), which combines vapor-phase chalcogen and liquid-phase metal precursors to enable faster experimentation with new dopants and growth chemistries. Using HyMOCVD, we identify novel etching mechanisms of salt growth promoters commonly used to boost grain size and growth rate, and we study WS₂ as a function of doping with vanadium acceptors.

(2.) We developed automated assembly of vdWHS using prepatterned materials grown at the wafer scale. We fabricated vdW solids of up to 80 individual layers with pre-designed shapes, composition, and interlayer twist. This enabled efficient spectroscopic assays of vdWHS and fabrication of twisted n-layer assemblies, where we observed atomic lattice relaxation of twisted 4-layer WS₂ at high twist angles ≥ 4°.

(3.) We have applied widefield hyperspectral microscopy to rapidly assess the quality and properties of MOCVD monolayers and heterostructures. We have also developed torsional force microscopy, an in-air AFM method to map the moire (surface or sub-surface) and atomic lattice with common hardware.