All-Carbon Patterning of HOPG on the Nanometer Scale with non-IPR Fullerenes

Abstract

Arrays of amorphous carbon defects were prepared on the basal plane of highly oriented pyrolytic graphite (HOPG) using Ga⁺ focused ion beam (FIB) writing. These defects were then used as pinning sites for non-IPR C₅₈ fullerene cages (with reactive adjacent pentagon rings) deposited onto the room temperature surface from a low-energy (<6 eV) mass-selected ion beam. Following deposition, a brief annealing step at 550 K increased the occupation of the FIB defects by allowing for pinning of additional C₅₈ cages diffusing from more weakly binding sites elsewhere on the surface. The overall pinning efficiency depends on the lattice constant of the FIB defect array. When the defect spacing approaches the mean gliding length of mobile C₅₈ cages (reflecting surface parallel velocity dissipation following hyperthermal impact on the superlubric HOPG) nearly complete decoration of the FIB defects can be achieved. Upon further heating to 1100 K, a significant fraction of the pinned C₅₈ can be transformed into non-volatile polymers of partially fused cages. Alternatively, heating the C₅₈ island arrays while exposing them to atomic hydrogen can largely remove the FIB-structured deposits by converting them into volatile fullerene hydrides. The results demonstrate a tunable, carbon-on-carbon patterning strategy with potential for nanodevice fabrication.