UC Berkeley

The exponentially increasing demand for smaller, faster, and more energy efficient electronic devices represents a monumental challenge in designing the next generation of post-silicon functional electronic materials. Traditionally, device architectures based on organic/inorganic semiconductors are fabricated using a top-down approach; their performance is inherently limited by the spatial resolution of photolithographic techniques. Fischer group’s goal is to understand, control, and to be able to harness the exceptional electronic/magnetic properties emerging from nanoscale graphitic materials by developing novel synthetic strategies toward graphene nanoribbons (GNR) via bottom-up synthesis from atomically defined molecular precursors. The semiconducting properties of GNRs can be modulated by varying their width, edge structure and the identity of atoms in the periodic lattice.

My thesis work will detail the power of organic synthesis in design of molecular precursors en route to GNRs, the nanoribbon formation analysis techniques, and the outlook toward application of GNRs in a low-power, tunneling field-effect transistor device architecture (Chapter 1). A large part of my work has aimed at developing new synthetic strategies to access heteroatom-substituted GNRs. After making advances toward BN-substituted GNR precursors, I have discovered a molecular scaffold which furnishes the first example of a surface-mediated C–N bond formation in the context of a 7-AGNR segment (Chapter 2). I have also prepared a series of molecular precursors that have led to the formation of a new family of nitrogen-substituted zigzag GNRs, which possess intriguing spin-separated states along the edges (Chapter 3). In addition to exploring heteroatom substitution, I investigated all-carbon GNR scaffolds that utilize topological band engineering concepts in order to explore new variables that will allow rational tuning of electronic properties in GNRs. I have prepared multiple precursors to continue the realization of topologically protected interface states in GNRs, which are generated by construction of a superlattice of well-defined ribbon segment heterojunctions (Chapter 4).