Binary self-assembled monolayers of alkanethiols on Au(111) studied by STM

C. VERICAT; F. REMES LENICOV; S. TANCO; G. ANDREASEN; L. VÁZQUEZ; M. E. VELA; R. C. SALVAREZZA

Acta Microscopica

Editorial

Año: 2003 vol. 12 p. 78 - 82

The surface structure of mixed mercaptopropionic acid and hexadecanethiol self-assembled monolayers (SAMs) on Au(111) has been studied by scanning tunneling microscopy (STM) complemented with electrochemical techniques. The STM images are strongly dependent on time and on the tunneling current and voltage. At relatively high tunneling resistance STM images change with time from a uniform contrast to two-contrast domain pattern. The surface coverage of the highest contrast phase is consistent with the hexadecanethiol surface coverage determinedby electrochemical techniques. At relatively low tunneling resistance, the two-contrast domain pattern slowly vanishes indicating that the process is completely reversible. The slow rate of the highcontrast phase formation suggests that molecular reordering takes place induced by the STM tip. The STM image contrast is dominated by both topographic and electronic effects.