Structural analysis of ionic-liquid/organic-monolayer interface by phase modulation atomic force microscopy utilizing a quartz tuning fork sensor

Abstract

Structural analysis of the interfaces between an ionic liquid (IL) and an organic monolayer was carried out by phase modulation atomic force microscopy (PM-AFM). A quartz tuning fork sensor with a sharpened tungsten tip was used as a force sensor instead of a Si cantilever. Topographic imaging of the monolayer-covered Si(111) substrate revealed that the PM-AFM is capable of imaging the atomic steps originating from the substrate in an IL. We also carried out force curve measurement using the PM-AFM in order to directly confirm the presence of solvation layers and revealed that at least 4 layers, each with a thickness of 0.77nm, were formed on the interface. In addition, we obtained topographic images at different driving frequencies and indicated that it is possible to image not only the sample surface but also the solvation layers formed on the IL/monolayer interface. © The Electrochemical Society of Japan, All rights reserved.