UC Berkeley

Global energy consumption for computing is growing at an unsustainable rate. Metal-oxide-semiconductor field-effect transistors (MOSFETs) are the foundation of integrated circuits (ICs) and have enabled the revolutionary development of digital electronics central to modern life. However, the energy efficiency of MOSFETs is inherently limited by their fundamental switching mechanism. To address global energy concerns, it is imperative to develop radically new, low-energy logic technologies. Promising low-energy switching mechanisms include the modulation of electron tunneling through an energy barrier and the storage of information via electron spin. Bottom-up synthesized graphene nanomaterials, including graphene nanoribbons (GNRs), are an exceptional candidate for these potentially transformative logic technologies as they feature rationally tunable and controlled electronic structures, exceptional transport properties, and long spin-decoherence lifetimes. However, fundamental components essential for the construction of bottom-up synthesized graphene nanomaterial-based ICs are currently underdeveloped.

This thesis presents new advances in the bottom-up synthesis of graphene nanomaterials for the next generation of electronics. Chapter 2 demonstrates a strategy to lower the energy of π-electron states in graphene nanomaterials. This critically prevents electron transfer to the underlying substrate that would otherwise occur and quench the magnetism of these materials. In chapter 3, a regioselective on-surface radical step-growth polymerization is developed and implemented to form a narrow band gap GNR. The electronic structure emerges from the precise arrangement of zero-modes originating from the [3]triangulene repeat unit. Chapter 4 harnesses this regioselective polymerization to form asymmetric GNRs that are promising candidates for new topological materials. Further annealing of these GNRs induces five-membered ring formation that transforms their electronic structure and affords metallic GNRs. Chapter 5 addresses critical challenges facing the development of graphene nanomaterial-based electronics. A strategy is presented to synthesize longer and more pristine GNRs using perdeuterated molecular precursors. This work also demonstrates the first example, to the best of our knowledge, of a kinetic isotope effect observed in an on-surface radical step-growth polymerization. Lastly, efforts toward a new platform for GNR-based sensing devices are detailed.