Supported Solid and Liquid Metal Films for Growth of Single-Layer Graphene and Boron Nitride Lateral Heterostructures.

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Non-technical Description: This project investigates the growth of graphene and hexagonal boron nitride (h-BN), as well as their heterostructures in the lateral directions, on thin metal films. Both of these two-dimensional materials are one-atom-thick crystals with their atoms arranged in a honeycomb structure. They have novel electronic, photonic and magnetic properties that can be exploited in next-generation technologies. The size and shape of individual graphene and h-BN crystallites are manipulated through variations in growth conditions to achieve desired properties for specific applications. Using the edges of existing crystallites as one-dimensional substrates for lateral growth of the other material enables formation of a wide variety of laterally heterostructured films including interleaved arrays of graphene and h-BN nanowires and graphene quantum dots in a h-BN matrix. This project trains one PhD student in fabrication and characterization of these unique materials. The principal investigator is collaborating with the "Science is Fun" program at Arizona State University to develop age-appropriate curriculum modules for Phoenix area K-12 students.Technical Description: This project employs cold-wall chemical vapor deposition (CVD) to grow single-layer monocrystalline graphene and hexagonal boron nitride (h-BN) lateral heterostructures onto thin metal films. The size and shape of isolated graphene and h-BN crystallites are tuned in order to use their perimeters as substrates for lateral heteroepitaxy of the other material. The research develops a capability that enables engineering of single-layer graphene/h-BN nanocomposites with controlled shapes, sizes and interface structure (i.e., zigzag or armchair) and with desirable properties. Graphene and h-BN are grown atop thin metal films deposited on refractory metal supports that are heated to temperatures both below and above the metal-film's melting temperature to assess the efficacy of CVD onto liquid metals for growth of the target structures. A variety of thin metal and alloy films are investigated to assess their effects on graphene, h-BN and heterostructure morphology. Real-time imaging during the growth in an environmental scanning electron microscope elucidates growth mechanisms. In combination with systematic investigation of films and heterostructures grown using cold-wall CVD, a comprehensive understanding of the fundamental science underpinning graphene, h-BN and heterostructure growth on both solid and liquid metal films is developed. Films and heterostructures are also characterized at the atomic level using aberration-corrected (scanning) transmission electron microscopy.