Dielectric properties of self-assembled layers of octadecylamine on mica in dry and humid environments

• Published in: The Journal of chemical physics 2005-09, Vol.123 (10), p.104706-104706-6
• Main Authors: Benitez, J. J., de la Fuente, O. Rodriguez, Díez-Pérez, I., Sanz, F., Salmeron, M.
• Format: Article
• Language: English
• ISSN: 0021-9606; 1089-7690
• DOI: 10.1063/1.1927507

Atomic force microscopy operating in noncontact electrostatic force mode was used to study the interaction of water with films of alkylamines and alkylsilanes on mica. The films efficiently block water adsorption except in exposed mica areas, where it strongly modifies the mobility of surface ions. We also studied the molecular orientation of octadecylamine molecules forming monolayers and multilayer islands. In monolayer films the molecules bind to mica through the amino group, producing a positive contact potential relative to mica (dipole pointing up). In multilayer films the methyl and amino group terminations are exposed in alternating layers that give rise to alternating values of the contact potential. These findings correlate with low and high friction forces measured in the methyl termination and amino terminations.