Unconventional Phases in Monolayer TMDs: From Colloidal Synthesis to Multiscale Analysis – PhaseCraft

Group IV transition metal dichalcogenide (TMD) monolayers have garnered significant attention due to their exceptional optoelectronic properties, arising from their stable hexagonal (1H phase) crystal structure, characterized by trigonal prismatic coordination of the transition metal atom. However, alternative crystal phases, such as the metastable 1T (1T’) phases, where metal atoms exhibit octahedral coordination, are emerging as a promising research area. These unconventional phases display intriguing properties like metallicity, semi-metallicity, superconductivity, and catalytic potential. Despite their promise, current synthetic methods for these monolayers are limited, especially in term of achieving high quality and for large-scale production. The PhaseCraft project aims to systematically explore and stabilize these unconventional TMD polymorphs through colloidal synthesis. This method enables scalable production and can be tuned to produce alloys, doped monolayers, and planar heterostructures. We will use complementary techniques to investigate structural and electronic properties across multiple scales, from the micrometer to the atomic level, with support from DFT calculations. High-resolution transmission electron microscopy (HR-TEM) and scanning tunneling microscopy/spectroscopy (STM/STS) will uncover atomic-level defects, crystal structures, and electronic behavior. In situ X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy will track phase transitions in real time under various conditions. Combining the tunability of colloidal synthesis with multiscale analysis will allow us to design and stabilize new unconventional phases of monolayer TMDs. The expected outcomes of PhaseCraft include not only the discovery of these new phases but also a deeper understanding of their structural and electronic properties, as well as their phase stability, paving the way for novel functional materials.