Technical: This project is to study growth of graphene on metal substrates such as nickel using the chemical vapor deposition (CVD) technique and subsequent transfer of the graphene layers to diverse types of materials such as semiconductor, metal, and plastics. Graphene is the hexagonal arrangement of carbon atoms in a one-atom-thick sheet. While there has been an explosion of research activities on graphene over the past a few years, the success of future fundamental research and applications of graphene is critically depending upon the capability to obtain continuously large-area, single-crystalline graphene sheets with controlled number of layers on arbitrary substrates. This project aims to achieve this goal. The research activities of the project include two complementary routes: One involves the direct investigation on the CVD growth, via time-dependent in-situ Raman characterization. The second involves structural analysis on both the graphene and metal substrate to provide feedback information while various synthesis parameters are tuned. The intellectual merits of the proposed activities include: (1) understanding of the CVD growth mechanism of the graphene on metal substrates (2) identification of optimal routes for graphene synthesis, (3) study of the effect of various defects to the electronic properties and of the nickel-graphene interface phenomena.
The project addresses basic research issues in a topical area of materials science with high technological relevance. If the large-area, single-crystalline graphene on insulating substrate is successful, tremendous opportunities will open up for the applications of graphene in electronics, solar cells, flexible displays, light emitting diodes. The project activities also offer an excellent opportunity for training of students in chemistry, material science, nanofabrication and electrical engineering. This work is expected to lead to a highly interdisciplinary and creative Ph.D. dissertation and learning experience for students from all levels to be educated in nanoscience and nanotechnology. Undergraduate students and high school students, including those from under-represented groups, will be recruited to participate in the proposed research. Investigations carried out in this research program will also serve as a basis for several topics for undergraduate and graduate courses.
Under this award, our group carried out very fruitful studies on the synthesis of graphene growth using the chemical vapor deposition (CVD) synthesis using metallic substrates. Better understandings on the growth mechanism was obtained regarding: (1) the role of the kinetic factors so that the differences between low pressure CVD (LPCVD) and atmospheric pressure CVD (APCVD) can be understood; (2) the role of hydrogen gas in the growth process and as a result monolayer graphene can be grown also with APCVD process by excluding hydrogen during the synthesis; (3) the role of the morphology and purity of the growth substrate so that graphene with better quality can be obtained; (4) the growth of bilayer and multilayer graphene on Cu envelope structure. At the same time, a novel, much more efficient and confident method was developed to distinguish AB-stacked vs. randomly rotated bilayer graphene using Raman spectroscopy. This study of graphene synthesis has also inspired us to apply knowledge obtained here in the synthesis of other two-dimensional materials such as hexagonal Boron Nitride (hBN), transition metal dichalcolgenides (TMD) and the hybrid structure of graphene and hBN, graphene and TMD. The fruitfulness of this study is also seen through the numerous collaborations that we have established with ~ twenty research groups all over the world, graphene, hBN and MoS2 samples have been provided to enable both their fundamental studies and applications. Under this award three graduate students and six postdocs have been partially supported to investigate the synthesis of graphene and two dimensional materials, the education and training have prepared them for their next step along their career path. Four local high school students have been participated on this project, and have been inspired by our research. The results of this investigation have helped the PI to develop the graduate course: "Science, Technology and Applications of Carbon Nanomaterials" at MIT, and also numerous guest lecture presentations. Based on the studied carried out under this award, several patents have been filed. Through the MIT industrial liason program, the PI has also disseminated knowledge obtained in this project to interested companies.
