Scanning tunneling microscopy and spectroscopy of wet chemical synthesized porous graphene nanoribbons in ultra-high vacuum

This thesis investigates wet chemically synthesized graphene nanoribbons (GNRs) on semiconductor substrates using scanning tunneling microscopy and documents the extensive maintenance required for the ultra-high vacuum chamber systems. After venting the ultra-high vacuum chamber system to atmosphere, numerous innovations and repairs were made to the chamber. An extended titanium sublimation pump was added to the scanning tunneling microscope chamber. The preparation chamber dipstick was redesigned. Challenges arose that included taking apart the preparation chamber ion pump, replacing two turbo pumps and resolving a challenging leak. The final bake-out procedure resulted in chamber base pressure of 9 ́10-11 Torr. Atomically precise porous GNRs are a new chemically synthesized variation for which the fabrication procedure yielding multiple pores in a single ribbon and the electronic details of the ribbon have not been reported. In this work, porous GNRs are dry contact transferred in ultrahigh vacuum to clean silicon and III-V semiconducting substrates and examined using UHV scanning tunneling microscopy (STM) and spectroscopy (STS). STM imaging confirms the expected porous structure and indicates a unique electronic feature at the graphene nanopores