Two-dimensional materials have garnered significant interest from both academia and industry due to their exceptional properties at atomic thicknesses, making them ideal candidates for a wide range of applications, such as electronics, optoelectronics, and catalysis. However, the controlled synthesis of 2D materials using chemical vapor deposition (CVD) remains a considerable challenge, primarily due to a limited understanding of growth mechanisms. This thesis presents strategies for engineering the structures of 2D materials, including hexagonal boron nitride (hBN) and transition metal dichalcogenides (TMDs), using CVD. Employing advanced characterization techniques and theoretical simulations, we elucidate the mechanisms underlying the CVD growth of 2D materials.

Briefly, the thesis...[ Read more ]

Two-dimensional materials have garnered significant interest from both academia and industry due to their exceptional properties at atomic thicknesses, making them ideal candidates for a wide range of applications, such as electronics, optoelectronics, and catalysis. However, the controlled synthesis of 2D materials using chemical vapor deposition (CVD) remains a considerable challenge, primarily due to a limited understanding of growth mechanisms. This thesis presents strategies for engineering the structures of 2D materials, including hexagonal boron nitride (hBN) and transition metal dichalcogenides (TMDs), using CVD. Employing advanced characterization techniques and theoretical simulations, we elucidate the mechanisms underlying the CVD growth of 2D materials.

Briefly, the thesis includes four main topics: 1) By controlling the precursor flux, we achieve structural evolution of hBN grown on molten copper surfaces. This enables the shape evolution of hBN single-crystal flakes from triangular to truncated triangular and, eventually, to circular shapes. The origins of center-aggregated adlayers are also observed and explained through theoretical models. 2) We manipulate the formation of quantum emissions in carbon-doped hBN by designing carbon-poor, standard, and carbon-rich growth regimes during CVD growth. This is accomplished by regulating carbon concentrations near the growth substrate surfaces. X-ray photoelectron spectroscopy (XPS) findings on carbon-doping levels align with quantum emitter densities determined through wide-field optical microscopy. 3) We introduce a gap-filling CVD method for synthesizing large-scale MoS₂/WS₂ heterostructure mesh with a high heterointerface density. Uniformly distributed gaps are generated through internal strain caused by the substitution of tellurium atoms in single-crystalline MoTe₂ with sulfur. High-resolution transmission electron microscopy reveals the coherent nature of the heterostructure mesh. 4) We propose a hydrogen-free ramping approach to enhance the monolayer growth of TMDs. Based on a combination of ex-situ and in-situ characterizations, hydrogen-free ramping facilitates the diffusion of transition metals and thus promotes the monolayer growth of TMDs. The strategies and mechanisms presented in this thesis offer valuable insights into the controlled synthesis of 2D materials and will be beneficial for their industrialization and practical applications.