Complex orientational ordering of C60 molecules on Au(111)

The orientation and adsorption site for C-60 molecules on Au(111) has been studied using low temperature scanning tunneling microscopy. A complex orientational ordering has been observed for molecules inside the "in-phase" (R0 degrees) domain. A 7-molecule cluster consisting a central molecule sitting atop of a gold atom and 6 tilted surrounding molecules is identified as the structural motif. The 2 root 3 x 2 root 3-R30 degrees phase consists of molecules bonding to a gold atomic vacancies with a preferred azimuthal orientation. The quasi-periodic R14 degrees phase is composed of groups of similarly oriented molecules with the groups organized into a 4 root 3 x 4 root 3-R30 degrees like super-lattice unit cell. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3639106]