ORDERING PROCESSES AT THE DECANETHIOL AU(111) INTERFACE/

Using variable temperature scanning tunnelling microscopy (STM), we st udied the ordering processes on thiol-covered Au(111) surfaces at both the mesoscopic and microscopic scale. Because of the chemical erosion accompanying the self-assembly process, thiol-covered gold surfaces p resent small depressions, a few nanometres in size and one gold layer in depth. These defects can be healed by heating the monolayer up to 3 50-370 K. By performing isothermal STM measurements at elevated temper ature (320-360 K), we followed the growth kinetics of the holes. The v acancy islands are found to coarsen by an Ostwald ripening mechanism, The molecular ordering of the thiol monolayers was also studied. The c oexistence of several stable molecular conformations at room temperatu re was revealed. The well-ordered molecular domains extend over 100-20 0 Angstrom. The dominant domain configurations contain two superstruct ures with four molecules per unit cell. The origin of the STM image co ntrast is discussed.