Photoinduced C–C Reactions on Insulators toward Photolithography of Graphene Nanoarchitectures

Abstract

On-surface chemistry for atomically precise sp² macromolecules requires top-down lithographic methods on insulating surfaces in order to pattern the long-range complex architectures needed by the semiconductor industry. Here, we fabricate sp²-carbon nanometer-thin films on insulators and under ultrahigh vacuum (UHV) conditions from photocoupled brominated precursors. We reveal that covalent coupling is initiated by C–Br bond cleavage through photon energies exceeding 4.4 eV, as monitored by laser desorption ionization (LDI) mass spectrometry (MS) and X-ray photoelectron spectroscopy (XPS). Density functional theory (DFT) gives insight into the mechanisms of C–Br scission and C–C coupling processes. Further, unreacted material can be sublimed and the coupled sp²-carbon precursors can be graphitized by e-beam treatment at 500 °C, demonstrating promising applications in photolithography of graphene nanoarchitectures. Our results present UV-induced reactions on insulators for the formation of all sp²-carbon architectures, thereby converging top-down lithography and bottom-up on-surface chemistry into technology