Atomically Dispersed Cobalt within a Bilayer of C₆₀

Individual cobalt atoms trapped within a bilayer of C₆₀ have been produced by the deposition of Co atoms onto a C₆₀ double layer supported on graphite. High-resolution scanning tunneling microscopy (STM) reveals two stable states of a single cobalt atom coordinated with three C₆₀ molecules, which is denoted as (C₆₀)₃Co. The diffusion of the cobalt atoms within the C₆₀ layers is highly limited, resulting in the effective capture of single cobalt atoms in the interstitial sites of the close-packed C₆₀ layers. Density functional theory calculations show that the Co atom is located in the tetrahedral void between two close-packed C₆₀ layers. The most stable configuration of (C₆₀)₃Co consists of two C₆₀ molecules from the top layer with the third C₆₀ from the bottom layer. A less stable configuration of (C₆₀)₃Co where all three C₆₀ molecules are from the top layer was also observed at room temperature.