Effect and Mechanism of Hydrogen-Assisted Sulfur Intercalation for Decoupling Graphene from Cu(111) Substrate: A First-Principles Study
XC Sun and XY Luo and YL Li and FP Yu and X Zhao, APPLIED SURFACE SCIENCE, 567, 150866 (2021).
Intercalation has been experimentally proven to be an efficient approach for decoupling graphene from metal substrates such as Cu, which enables the easy transfer of graphene from a substrate. Thereby we propose a simple and effective method for injecting the H2S gas under an annealing environment to form sulfur compound intercalations, to help decouple graphene from the Cu substrate. Using density functional theory calculations, two different S-intercalating mechanisms, direct S intercalation and Hydrogen (H)-assisted S intercalation, have been found to occur at the zigzag and armchair edges of graphene, respectively. By forming various two-dimensional (2D) sulfide (Cu2S, CuS, and Cu2S) intercalations depending on the temperature and S concentration, the electron interaction between the Cu substrate and graphene as well as the exfoliation energy of graphene from the Cu substrate can be effectively reduced. This allows graphene to decouple from the Cu substrate and become almost free-standing with a neutral charge under controlled experimental conditions. The stability of the sulfide intercalations has been proven by thermodynamic and kinetic simulations. H-assisted S intercalation may promote the subsequent transfer of graphene, enabling the practical application of large-sized graphene sheets grown by chemical vapor deposition on metal substrates.
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