Growth behaviours of pentacene films confined in engineered shapes of ionic-liquid in vacuum

Abstract

Ionic liquid (IL) films not only in the form of micro-droplets, but also of a homogeneously thick submicron-layer were deposited under vacuum on indium tin oxide (ITO) substrates by chemically modifying their wettability to the substrate. When pentacene was deposited on these IL-coated ITO substrates, pentacene crystals were grown via the IL. Depending on the shape and size of the IL films: a small-droplet (ϕ: 5 μm), a large-droplet (ϕ: 20 μm) and a homogeneously thick layer (about 0.1 μm in thickness), there were found significant differences in the growth behaviour of pentacene and the resultant adhesion ability of these pentacene films to the substrate, the mechanism of which is discussed with the aid of in situ observation of the crystal growth process in the IL in view of the wettability of the IL, the nucleation and the subsequent growth of the pentacene crystals.