Real Space Demonstration of Induced Crystalline 3D Nanostructuration of Organic Layers

Abstract

The controlled 3D nanostructuration of molecular layers of the semiconducting molecules CH (pentacene) and N,N'-dioctyl-3,4,9,10-perylene tetracarboxylic diimide (PTCDI-C8) is addressed. A tip-assisted method using atomic force microscopy (AFM) is developed for removing part of the organic material and relocating it in up to six layer thick nanostructures. Moreover, unconventional molecular scale imaging combining diverse friction force microscopy modes reveals the stacking sequence of the piled layers. In particular, we unambiguously achieve epitaxial growth, an issue of fundamental importance in thin film strategies for the nanostructuration of more efficient organic nanodevices.

Subnanometer Resolution and Enhanced Friction Contrast at the Surface of Perylene Diimide PDI8-CN2 Thin Films in Ambient Conditions

“…Therefore, albeit our work does not tightly compare the onset of wear for thin films of PTCDI-C8 and PDI8-CN 2 , it nonetheless gives indications for an effective stability of the PDI8-CN 2 surface under the mechanical action of the AFM tip. On one hand, we recognize that the lower coverage of PTCDI-C8 in Paradinas et al might contribute to make such system more vulnerable to mechanical damage compared to the thicker PDI8-CN 2 films of the present work. On the other hand, considering that surface wear is assisted by the adsorbed water and is usually hindered by small interfacial friction, potential differences between PTCDI-C8 and PDI8-CN 2 might also arise from the occurrence of systematically smaller friction forces between the tip and the core-cyanated material or from a higher resistance of PDI8-CN 2 against moisture adsorption/O 2 intrusion.…”

“…On one hand, we recognize that the lower coverage of PTCDI-C8 in Paradinas et al might contribute to make such system more vulnerable to mechanical damage compared to the thicker PDI8-CN 2 films of the present work. On the other hand, considering that surface wear is assisted by the adsorbed water and is usually hindered by small interfacial friction, potential differences between PTCDI-C8 and PDI8-CN 2 might also arise from the occurrence of systematically smaller friction forces between the tip and the core-cyanated material or from a higher resistance of PDI8-CN 2 against moisture adsorption/O 2 intrusion. This appears in line with arguments that ascribe to core-cyanated materials a higher resistance against oxidation induced by the ambient gases action .…”

“…It is finally intriguing to discuss the above results in light of recent FFM experiments by Paradinas et al involving the core-unsubstituted parent material PTCDI-C8 . In these studies, few-layers-thick PTCDI-C8 thin films appear extremely vulnerable to the sweeping effect of the AFM tip so that the surface molecular packing is irreversibly damaged in the repulsive regime (positive loads, F N > 0).…”