Carbon chains and graphene nucleus synthesized on Ni(111) surface

TL;DR

This study reports the direct observation of linear carbon chains on Ni(111) surfaces using STM, revealing their stability, formation process, and coexistence with graphene and nickel carbide, supported by DFT calculations.

Contribution

First direct STM observation of carbon chains on Ni(111), elucidating their formation, stability, and coexistence with graphene and nickel carbide phases.

Findings

Carbon chains are stable at room temperature.

Heating reduces chains and promotes graphene and carbide formation.

STM directly visualized chain mobility and coexistence with other phases.

Abstract

Linear chains of about 10-13 carbon atoms were predicted to be the most favorable phase on different metal surfaces prior to graphene nucleation. However, unlike the graphene that widely studied both theoretically and experimentally, carbon chains on metal surfaces were not directly studied by STM yet. Here we fill in the gap and report on STM experiments of linear carbon chains synthesized on Ni(111) through on-surface coupling of dehydrogenated propene molecules. Identification of chains was supported with DFT calculations and the proposed models consist of 12 carbon atoms, possibly covered by hydrogen atoms. Heating to 580 K leads to dramatic decrease of carbon chains and new phase appearance - graphene nucleus coexisted with nickel carbide. After flash annealing to 773 K (temperature of graphene synthesis), a small number of chains were presented on the Ni(111) surface, together with graphene islands and nickel carbide. The carbon chains are stable at room temperature and their mobility was directly observed by STM.