STRUCTURES AND DYNAMIC FORMATION PROCESSES OF PORPHYRIN ADLAYERS ON IODINE-MODIFIED AU(111) IN SOLUTION - IN-SITU STM STUDY

The structures and dynamic formation processes of adlayers of tetrakis (N-methylpyridinium-4-yl)-21H,23H-porphine (TMPyP) on both bare Au(111 ) and iodine-modified Au(111) in perchloric acid have been investigate d in detail by using in situ scanning tunneling microscopy (STM). High ly-ordered TMPyP arrays formed on iodine-modified Au(111), whereas dis ordered adlayers were consistently found on bare Au(111) surface. High -resolution STM images revealed the characteristic internal shape and orientation of each TMPyP molecule in ordered adlayers. Time-dependent in situ STM allowed direct observation of the dynamics of the self-or dering processes. Before the most stable adlayer was established in a relatively small domain, several structural changes were found to occu r, including the formation of a one-dimensional ordered chain at an ea rly stage and several phase transitions in the ordered adlayers. Once the most stable adlayer was formed as a nucleus in a domain, two-dimen sional growth of the domain extended over the entire area of the terra ces with the final packing arrangement.