Single-layer monocrystalline graphene and hexagonal boron nitride (h-BN) lateral heterostructures will be grown using cold-wall chemical vapor deposition (CVD) onto thin metal films deposited onto refractory metal supports. Strategies will be developed to tune the size and shape of isolated graphene and h-BN crystallites in order to use their perimeters as substrates for lateral heteroepitaxy of the other material. In this manner, a wide variety of lateral graphene/h- BN heterostructures can be grown with control over domain size, shape and interface structure (i.e., zigzag or armchair). This capability will enable engineering of single-layer graphene/h-BN nanocomposites with desirable properties. Example architectures include interleaved nanoribbons formed by sequential lateral heteroepitaxy of h-BN and graphene using the edges of a hexagonal graphene nanoflake as 1D 'substrates', graphene quantum dots in a h-BN matrix and h-BN 'anti-dots' in a graphene matrix. Cold-wall CVD from CH4/H2/Ar mixtures at up to atmospheric pressure will be employed for graphene growth. h-BN growth will substitute borazine (B3N3H6) for methane. Single layer graphene and h-BN will be grown atop thin metal films deposited in situ that are heated to temperatures both below and above their melting points to assess the efficacy of CVD onto liquid metals for growth of the target structures. A variety of thin metal and alloy films will be employed to assess their affects on graphene, h-BN and heterostructure morphology. Realtime imaging during growth in an environmental scanning electron microscope will elucidate 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 will be developed. Films and heterostructures will be characterized at the atomic level using aberration-corrected (scanning) transmission electron microscopy. Particular attention will be paid to characterizing the structure and abruptness at lateral heterostructure interfaces. Simple back-gated field effect devices will be fabricated to correlate electronic transport with structure. Intellectual Merit Recent advances in CVD of single-layer graphene have yielded ~mm-sized monocrystals, suggesting that pathways toward wafer-scale synthetic graphene are on the horizon. However, the potential for application of 'bulk' single-layer graphene to electronic devices is limited by the absence of a bandgap. Graphene nanoribbons exhibit a bandgap and theoretical predictions of novel and exciting electric, magnetic and optical properties in laterally nanostructured singlelayer graphene, h-BN and composites of these materials abound. However, these structures lack a facile synthetic technique. This project addresses these deficiencies. Broader Impacts Developing rational synthetic methods for defining lateral heterostructures in the graphene/h-BN material system will enable manipulation of the electric, magnetic and optical properties of single-layer films. This capability will facilitate engineering of desirable functionalities that could have enormous technological impact. One PhD student will be trained in synthesis and characterization of advanced 2D materials. Meaningfully involving undergraduate researchers will not only provide invaluable training and exposure to the joy of discovering new knowledge, but will positively impact the PhD student through the mentoring opportunity provided. In addition, the PI will link with the highly successful ASU Science is Fun program to develop age-appropriate curriculum modules for Phoenix area K-12 students. This program impacts over 104 students annually. About half of these students are members of groups underrepresented in STEM disciplines. This is an MPS-GRSV request to support the PhD research of Emanuel (Manny) Borcean. Manny will begin his third year in the Physics PhD program this August and is completing the transition from coursework to full time research. He is currently supported as a teaching assistant and even with his teaching responsibilities, he has initiated new lines of research involving graphene growth on single crystal Ge surfaces and hexagonal boron nitride (h-BN) growth on Cu films electrodeposited on W supports. He was instrumental in the upgrade to the UHV CVD system being employed by the PhD student supported by the parent award, Shantanu Das, to facilitate growth of h-BN. He is currently developing procedures for h-BN growth on the supported electrodeposited Cu films so that he and Shantanu can collaboratively explore h-BN grown on Cu. The eventual plan is for Shantanu to lead investigations into growth of graphene, h-BN and lateral heterostructures of these materials on supported solid and liquid metal films while Manny broadens the scope of the investigation by pursuing similar work on single crystal Ge surfaces. Operations support for Manny's research (facility recharge fees, materials & supplies, etc.) will derive from the parent award. Graphene growth on single crystal Ge surfaces is relatively unexplored and h-BN growth on these substrates is almost completely unexplored. The few existing reports indicate that both graphene and h-BN align crystallographically to the Ge substrate, which suggests a high probability of success in forming high-quality single-layer lateral graphene/h-BN heterostructures. Manny has also suggested that we explore h-BN growth on Si, which to our knowledge has not been attempted. Successful growth of high quality h-BN on Si could provide a pathway toward epitaxial integration of graphene or other 2D materials with Si. The immediate impact of GRSV support will be to free Manny from his teaching responsibilities. Although he enjoys teaching and is good at it, he would like to more fully direct his energies to his PhD research. In addition, Manny and Shantanu make a strong team. They bring complementary skills to the project. Shantanu's energy combined with Manny's innate facility with instrumentation and knack for experimental work is an unbeatable combination. This supplement support could have broad scientific impact by enabling Manny to define the fundamental science of lateral heteroepitaxy of 2D materials on single crystal surfaces. This is a request to continue the MPS-GRSV support for Emanuel (Manny) Borcean for a second year. Manny will begin his fourth year in the Physics PhD program this August and has completed the transition from coursework to full time research. He was supported by a MPSGRSV during the past year when he made a significant advance in the synthesis of hexagonal boron nitride (h-BN) on recrystallized Cu films using cold-wall CVD. This advance will enable us to explore the fundamental growth science of this material and the fabrication of a variety lateral heterostructures with graphene. In addition, we anticipate that his development of a reproducible method for h-BN synthesis using the industrially-preferred cold wall CVD technique, rather than the far more commonly employed hot wall CVD method, is likely to have broad impact. Operations support for Manny's research (facility recharge fees, materials & supplies, etc.) will continue to derive from the parent award. Our immediate goals are to explore h-BN growth on recrystallized Cu films supported on refractory metal substrates and to explore growth of lateral graphene on h-BN and h-BN on graphene heterostructures. These lateral heterostructures will employ the edges of existing crystallites as one-dimensional substrates for lateral heteroepitaxy of the other material. Time permitting, we will also explore graphene and h-BN growth on single crystal Ge surfaces. It is believed that both graphene and h-BN align crystallographically to single crystal Ge substrates, which suggests a high probability of success in forming high-quality single-layer lateral graphene/h-BN heterostructures. Manny has also suggested that we explore h-BN growth on Si, which to our knowledge has not been attempted. Successful growth of high quality h-BN on Si could provide a pathway toward epitaxial integration of graphene or other 2D materials with Si. The primary impact of GRSV support will be to enable Manny to continue to focus his full energy on research. The other alternative open to him is to serve as a department of physics teaching assistant. Although he enjoys teaching and is good at it, he has made more rapid progress, and will continue to do so, with renewed GRSV support. He will continue to collaborate with Shantanu Das, the other PhD student involved in the project as Shantanu winds up his PhD. Shantanu is transferring his knowledge of graphene growth to Manny as he writes his dissertation. Manny and Shantanu make a strong team. They bring complementary skills to the project. Shantanu's energy combined with Manny's innate facility with instrumentation and knack for experimental work is an unbeatable combination.
|Effective start/end date||7/1/14 → 6/30/19|
- National Science Foundation (NSF): $504,944.00
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