Low-Temperature Removal of Dissociated Bromine by Silicon Atoms for an On-Surface Ullmann Reaction

On-surface Ullmann-type reactions are widely used to fabricate various carbon nanostructures in a bottom-up approach by conjugating small hydrocarbons via dehalogenation. In the reaction, the dissociated halogen atoms remain on the substrate and are usually removed by high-temperature annealing. Here, we demonstrate an alternative method in which most of bromine atoms can be desorbed from Au(111) just by depositing silicon atoms. A combination of scanning tunneling microscopy and density functional theory calculations revealed that the highly volatile silicon tetrabromine is synthesized and consequently desorbs from the surface even at room temperature. This low-temperature removal of the halogen atoms may increase flexibility in on-surface chemical reactions toward synthesis and characterization of further functionalized carbon nanomaterials.