The structures of a C$_{60}$ monolayer on Au(111)*

The in-phase and (2$\surd $3x2$\surd $3)R30\r{ } structures of monolayer C$_{60}$ on Au(111) have been studied by scanning tunneling microscopy and dynamical low energy electron diffraction. The in-phase domains exhibit a (2x2) superlattice in high resolution STM images at 57K, in which one of the four molecules in the unit cell has a three-lobe intramolecular shape. After annealing at 663K, most of the monolayer was converted to R30\r{ } domains. The C$_{60}$ molecules in the (2$\surd $3x2$\surd $3)R30\r{ } domains image as random bright or dim objects, with a 50:50 ratio of bright to dim. At room temperature, there are conversions from bright to dim and vice versa, but such conversions are suppressed at 57K. The dynamical LEED analysis of (2$\surd $3x2$\surd $3)R30\r{ } structure will be presented.