Two-dimensional materials find use in the areas of electronics, energy storage, sensors, and catalysis due to their unique properties near the monolayer limit. The production and general application of certain 2D materials is bottlenecked by the inability to scale production. Discovery and optimization of alternate synthesis methods is paramount to bring emerging materials into technological maturity Currently, powdered materials use cost-intensive production methods with low yields and thin-film materials range in domain size from nanometer to micrometer which in insufficient for applications. In this dissertation, we explore the novel and direct synthesis of molybdenum, tungsten, and vanadium-based MXenes(2D metal carbides/nitrides)/MXene-like material carbon foam composites as well as the wafer-scale growth of transition metal dichalcogenides(TMDs). We studied the factors that influenced the morphology of carbon foams made via a sol-gel method with reducing sugars and metal precursors. We determine the conditions that are most amenable to producing suitable foam resins for pyrolysis. From there, the carbon scaffold was functionalized with catalytic metal nanoparticles for the synthesis of carbon nanotubes. This sol-gel method was then applied to molybdenum, tungsten, and vanadium oxides to produce MXenes. Studies affecting the full reduction, carburization, and resulting crystal polytype were also conducted. X-ray diffraction and EDX confirmed the synthesis of hexagonal Mo2C required no reductive gases while the tungsten and vanadium compounds required it. Various crystal polytypes were noted and the study was concluded with attempts to form metal nitride variants.
To achieve wafer-scale coverage of MoS2 and WS2, we employed a chelant-enhanced chemical vapor deposition technique. Metal thiols were combined with chelating agents of varying chain length in a DMSO solution, spun coat onto a SiO2/Si wafer, and annealed under vacuum. Molybdenum was found to form films while tungsten proved more difficult. The samples were characterized via Raman spectroscopy, SEM, AFM, and STEM.
In summary, this work produced two alternative synthetic routes for MXenes and TMDs and elucidated the factors/conditions that affect reduction and carburization (MXenes) and wafer-scale growth (TMDs). The sol-gel and chelant enhanced methods can be employed to produce compounds in the same material family.