Nanometer-scale phase separation in mixed composition self-assembled monolayers

Mixed composition monolayers of similar n-alkanethiols on are formed by self-assembly. While the average surface composition of these films accurately reflects the composition of the deposition solution, scanning tunneling microscopy and secondary ion mass spectroscopy measurements show that the films phase separate on the nanometer scale. Scanning tunneling microscopy has been used to follow molecular motions within these films. We discuss our observations in terms of the formation and stability of the phase-segregated domains, and their potential importance in nanoscale applications.