Morphological Study of a Self-Organized Corrole Film on a Gold Crystal, both in Solution and after Solvent Evaporation

Abstract

The morphology of the film created by the aggregation of corrole molecules from ethanol solution onto the surface of gold substrate was studied by scanning tunneling microscopy both: (i) in situ, namely in quasi-equilibrium (wet sample), and (ii) ex situ, i.e., removing the substrate from the fluid cell and leaving the residual amount of solution on the substrate to desiccate (dry sample). Despite the different conditions, the morphology of the corrole overlayer formed on the film of molecules is reminiscent, in both cases, of the leopard skin; the "speckles" are actually areas where the molecular overlayer of flat molecules is not completed. We quantitatively compared these two similar morphologies by studying the power spectral density of the images, the fractal dimension D P of the hole perimeters, and the cumulative distribution function of the hole areas. We found that the last layer of both films, in spite of very different formation conditions, differed from each other only by a scale factor.