ESE PhD Thesis Defense: “Chemical vapor deposition synthesis of graphene and transition metal dichalcogenides and their applications”

2D materials is a rapidly expanding class of materials that have captivated academia and industry with their ultrathin nature and remarkable properties. Graphene, the first discovered material, shows exceptional mechanical strength and superior electrical properties, presenting exciting probabilities in many applications. Combined with its large surface area and biocompatibility, graphene is particularly promising for the development of highly sensitive and selective biosensors. However, the application of graphene is limited by its lack of a bandgap, making it unusable for advanced logic circuits. 2D materials beyond graphene are thus being explored. Transition metal dichalcogenides (TMDs) are representative candidates possessing a variety of properties including tunable bandgaps. Conventionally, both graphene and TMDs are produced by mechanical exfoliation, but this method is low-yield and not suitable for large-scale applications such as biosensing. Therefore, a reliable synthesis strategy for these materials is urgently needed. In this thesis, synthesis of graphene and TMDs by chemical vapor deposition (CVD) is explored. The CVD synthesized graphene sheet has monolayer structure which can be inch scale in size, enabling the scalable fabrication of graphene biosensors. We develop the fabrication process of graphene biosensors and explore their biosensing applications, where the sensors are used to study the interaction between a specially designed water-soluble mu opioid receptor (wsMOR) and G-protein. The biosensors are able to record the in vitro interaction between the two molecules with high sensitivity. The CVD growth of TMDs is also investigated. Rapid growth of inch-scale monolayer MoSe₂ continuous film has been synthesized on insulating substrates, based on a spin-coating, NaCl assisted CVD approach. This approach is promising to be extended to the growth of other semiconducting TMDs, benefit to the batch production of large-area TMD electronics. Additionally, we studied the CVD synthesis of TMDs with controlled layer numbers at controlled locations. Various approaches are used to demonstrate the high quality of the materials and field-effect transistor measurements indicate their potential in making advanced electronic devices.