RUI: A New Approach for the Synthesis of Heteroatom-Doped Graphene and Lateral Heterojunctions

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Nontechnical Description: Graphene is the first discovered two-dimensional material with many exotic properties, however, its flexibility and practical applications remain restrained by some of its specific characteristics. Substitutional doping of graphene with heteroatoms (atoms from chemical elements different from the host material atoms) is one of the most fascinating strategies for tuning graphene's properties and hence expanding its applications. This project investigates the synthesis of heteroatom-doped graphene and related lateral junctions using heteroatom-containing source materials, which is a novel synthesis approach and enhances the capabilities for controlling the doping. This research also provides an atomic-scale understanding of the structural and electronic properties, as well as their interrelations. The realization of controlled synthesis of heteroatom-doped graphene and atomic-scale insights into their properties promote the development of graphene-based devices for electronics, energy storage, and catalysis. This project strengthens the materials science research at California State University Northridge, which is a minority serving institution, and provides collaborative research opportunities for graduate and undergraduate students. In addition, K-12 students from local schools receive exposure to cutting-edge research activities and advanced scientific facilities via summer activities.Technical Description: Precisely controlling the doping properties is pivotal toward practical applications of graphene. Doping properties strongly depend on synthesis approaches, heteroatom sources, and synthesis parameters. It is an urgent task to explore new synthesis approaches and new heteroatom sources in order to achieve enhanced control over the doping strategies. In addition, two-dimensional graphene p-n heterojunctions are the key components for graphene-based electronics, which further motivates the development of bottom-up growth approaches for these heterojunctions. The objectives of this research are to develop optimized synthesis strategies for heteroatom-doped graphene and related lateral heterojunctions from heteroatom-containing sole precursors, which is a novel and effective synthesis approach, as well as to gain atomic-scale insights into the correlations between doping alternatives and electronic properties. To accomplish these goals, the main research activities include: (1) optimize the synthesis by employing a series of precursor/metal systems under varied synthesis conditions and identify the dependence of structural and doping properties (concentration, spatial distribution, and configuration) on precursors, substrates, and synthesis parameters; (2) explore electronic properties (band structure, charge carrier density, work function) by combining scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy, Raman spectroscopy, and angle-resolved photoemission spectroscopy measurements; (3) improve the synthesis of graphene lateral p-n heterojunctions using sole precursors, and characterize the atomic structure and band alignments at the interfaces of lateral heterojunctions by using STM measurements.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.