DOMAIN AND MOLECULAR SUPERLATTICE STRUCTURE OF DODECANETHIOL SELF-ASSEMBLED ON AU(111)

Annealed organic monolayers of dodecanethiol (CH3(CH2)11SH) self-assem bled on Au(111) have been investigated by scanning tunnelling microsco py. By using very high tunnelling resistances (TOMEGA) we find evidenc e of well-ordered molecular domains at room temperature and observe tw o different types of c(4 x 2) superlattice structures with the same re ctangular unit cell. In contrast to theoretical calculations each unit cell contains four inequivalent molecules. Possible reasons for this discrepancy are discussed.