Noncontact atomic force microscopy investigation of phase-separated alkanethiol self-assembled monolayers with different head groups

We investigated alkanethiol phase-separated SAMs (PS-SAMs) with different head groups using noncontact atomic force microscopy (NC-AFM). Two kinds of PS-SAMs were prepared composed of 1-dodecanethiol (C-12)/3-mercapto-1-propanol (C3OH) and C-12/11-mercapto-1-undecanol (C11OH). We obtained the topographic, energy dissipation, and surface potential (SP) images of each sample. All the images clearly showed the feature of phase separation. Additionally, in the case Of C-12/C11OH PS-SAMs, the tip-to-sample distance dependence of frequency shift (Deltaf) and energy dissipation were measured on each domain, which also exhibited a difference in molecular species. We discussed them in terms of the difference ill the molecular arrangement, dipole moment and hydrophobic/hydrophilic properties of the head groups.