title: Bottom-up formation of robust gold carbide.
abstract: A new phenomenon of structural reorganization is discovered and characterized for a gold-carbon system by in-situ atomic-resolution imaging at temperatures up to 1300 K. Here, a graphene sheet serves in three ways, as a quasi transparent substrate for aberration-corrected high-resolution transmission electron microscopy, as an in-situ heater, and as carbon supplier. The sheet has been decorated with gold nanoislands beforehand. During electron irradiation at 80 kV and at elevated temperatures, the accumulation of gold atoms has been observed on defective graphene sites or edges as well as at the facets of gold nanocrystals. Both resulted in clustering, forming unusual crystalline structures. Their lattice parameters and surface termination differ significantly from standard gold nanocrystals. The experimental data, supported by electron energy loss spectroscopy and density-functional theory calculations, suggests that isolated gold and carbon atoms form - under conditions of heat and electron irradiation - a novel type of compound crystal, Au-C in zincblende structure. The novel material is metastable, but surprisingly robust, even under annealing condition.
authors.affiliation: Institute of Optoelectronics, Ulm University, 89081 Ulm, Germany.
authors.forename: Benedikt
authors.initials: B
authors.lastname: Westenfelder
authors.affiliation: Central Facility of Electron Microscopy, Ulm University, 89081 Ulm, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Biskupek
authors.affiliation: Department of Physics, University of Vienna, 1090 Vienna, Austria.
authors.forename: Jannik C
authors.initials: JC
authors.lastname: Meyer
authors.affiliation: Central Facility of Electron Microscopy, Ulm University, 89081 Ulm, Germany.
authors.forename: Simon
authors.initials: S
authors.lastname: Kurasch
authors.affiliation: Institute of Theoretical Chemistry, Ulm University, 89081 Ulm, Germany.
authors.forename: Xiaohang
authors.initials: X
authors.lastname: Lin
authors.affiliation: Institute of Optoelectronics, Ulm University, 89081 Ulm, Germany.
authors.forename: Ferdinand
authors.initials: F
authors.lastname: Scholz
authors.affiliation: Institute of Theoretical Chemistry, Ulm University, 89081 Ulm, Germany.
authors.forename: Axel
authors.initials: A
authors.lastname: Gross
authors.affiliation: Central Facility of Electron Microscopy, Ulm University, 89081 Ulm, Germany.
authors.forename: Ute
authors.initials: U
authors.lastname: Kaiser