Intercalation Chemistry of Tetrahedral Transition Metal Chalcogenides

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Tetrahedral transition metal chalcogenides (TTMCs), which have a common layered structural motif that could carry novel functionalities on account of the $d$-orbital filling. These metal chalcogenide layers can be held together either by pure van der Waals forces, ionic forces, or even hydrogen bonding, depending on the guest species intercalated in between the layers. Unlike transition metal dichalcogenides (TMDs), TTMCs have been less explored with respect to their synthesis, chemical reactivity, and physical properties. Structurally, TTMCs contain the transition metal in a square lattice and typically crystallize in tetragonal or orthorhombic structures on account of the square lattice. Some extraordinary properties they exhibit include superconductivity, metallic conductivity, and itinerant ferromagnetism.

In this dissertation work, we demonstrate that using kinetically controlled soft-chemistry routes, single crystal form of FeS is prepared for the first time. Furthermore, using similar route, we expand the binary TTMC family from Fe to Co, preparing the anti-PbO type of CoSe and CoS for the first time. Using these binary compounds, we demonstrate that TTMCs can serve as excellent hosts for intercalation chemistry by preparing alkali bases interacted iron chalcogenides. Upon intercalation, the new compounds show vastly different properties from the host, such as enhanced superconductivity or coexistence of superconductivity and long-range magnetic ordering. This work provides a framework for designing new binary and heterolyared TTMCs.