NANOMETER-SCALE PHASE-SEPARATION IN MIXED COMPOSITION SELF-ASSEMBLED MONOLAYERS

Mixed composition monolayers of similar n-alkanethiols on Au(111) are formed by self-assembly. While the average surface composition of thes e films accurately reflects the composition of the deposition solution , scanning tunneling microscopy and secondary ion mass spectroscopy me asurements show that the films phase separate on the nanometer scale. Scanning tunneling microscopy has been used to follow molecular motion s within these films. We discuss our observations in terms of the form ation and stability of the phase-segregated domains, and their potenti al importance in nanoscale applications.