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Abstract: 

Precise control of chemical doping and surface ionic behavior at the atomic scale opens new avenues for designing functional quantum and molecular materials. In this talk, I will present how bottom-up molecular synthesis combined with scanning probe microscopy enables direct visualization and manipulation of charge and structure in graphene-based nanostructures. Using molecular precursors, we achieve atomically defined graphene nanoribbon heterojunctions through controlled on-surface reactions and thermally induced bond rearrangement, allowing systematic tuning of band alignment and dopant distribution verified by bond-resolved STM, nc-AFM, and tunneling spectroscopy. Extending this chemical control to dynamic regimes, gate-tunable graphene field-effect platforms are used to reversibly ionize and reposition individual molecules, creating programmable surface ionic configurations that modulate the local electronic environment. Together, these results establish a coherent framework for atomic-level chemical control and charge manipulation in low-dimensional materials, opening new opportunities for designing functional quantum and electronic architectures.