Ultrafast Terahertz Microscopy of Atomically Precise Graphene Nanoribbons

This PhD thesis develops terahertz scanning tunnelling microscopy (THz-STM) to study electron dynamics in atomically precise graphene nanoribbons, combining atomic-scale spatial resolution with sub-picosecond time resolution. In THz-STM, a phase-stable single-cycle THz pulse coupled to the STM tip replaces the static bias, driving ultrafast tunnelling currents. The thesis describes generating intense THz pulses by optical rectification in lithium niobate, sub-20 fs electro-optic detection, and a practical guide to THz-STM and THz scanning tunnelling spectroscopy measurements. Seven-atom-wide armchair graphene nanoribbons (7-AGNRs) were grown by on-surface synthesis on Au(111), with growth conditions optimised to give isolated ribbons. Pairs of wire-grid polarizers controlled the THz field strength at the tip. The work lays the groundwork for exploring new quantum materials on their natural length and time scales.