Kumagai, Takashi; Janina N. Ladenthin, and Ikutaro Hamada:
Phys. Rev. Materials 2, 093403 (2018), pp.6;
Methane is the simplest hydrocarbon and its aggregation structures are determined merely by van der Waals (vdW) interaction. Here we present the direct observation of a vdW two-dimensional crystal and small clusters of methane on Cu surfaces using a low-temperature scanning tunneling microscope. Methane shows a hexagonal molecular-packing structure on the Cu(110) and Cu(111) surfaces. However, methane preferentially forms a dimer and a trimer on the Cu(110)-(2×1)-O added-row structure, indicating different aggregation behavior from the bare Cu surfaces. The adsorption structures are examined in detail by density functional theory calculations, providing atomistic insights into the adsorption geometry and aggregation mechanism of methane on the Cu surfaces, which are governed by a subtle balance between the intermolecular and molecule–surface interactions.
The original publication is available by link DOI: 10.1103/PhysRevMaterials.2.093403