Elucidating the dynamical equilibrium of C-60 molecules on Ag(111)

作者：Pussi K^*; Li H I; Shin Heekeun; Loli L N Serkovic; Shukla A K; Ledieu J; Fournee V; Wang L L; Su S Y; Marino K E; Snyder M V; Diehl R D

来源：Physical Review B, 2012, 86(20): 205406.

DOI：10.1103/PhysRevB.86.205406

We have used scanning tunneling microscopy (STM), low-energy electron diffraction (LEED), and density functional theory (DFT) to elucidate the structure and thermodynamics of the (2 root 3 x 2 root 3) R30 degrees phase of C-60 on Ag(111), which consists of a mixture of molecules in two different site/orientation states. The structure analysis identifies the two types of molecules as (1) sitting on a vacancy with a hexagon face down and (2) sitting on a top site with a C-C bond down. The molecules flip between the two states at a temperature-dependent rate. We show using a thermodynamic analysis that the two states differ by 0.07 eV and are separated by an energy barrier of 0.84 eV. Their dynamical equilibrium involves the diffusion of surface vacancies between C60 molecules, producing spatially and temporally correlated flipping events.

• 出版日期2012-11-5