Molecule assembly structure and tilt geometry evaluation of 5,6,7-trithiapentacene-13-one (TTPO) / Pentacene-Quinone on Au(111) with NC-AFM

Using non-contact atomic force microscopy (NC-AFM) the 3D molecular structure, tilt and assembly details of a new pentacene-based organic semiconductor, 5,6,7-trithiapentacene-13-one (TTPO) adsorbed on Au(111) were determined. 3D AFM force maps of individually resolved molecular orbitals were acquired to visualize the complete adsorption structure. Robust, thermally stable, and highly inert to photo-oxidation, TTPO is a very promising organic semiconductor. When adsorbed on a gold electrode, scanning tunneling microscopy (STM) experiments and first-principle computation reveal a novel 3-D angular assembly of the TTPO molecules, with the long axis of the molecule parallel to the gold surface, distinctive from any previously observed pentacene and pentacene derivative assemblies. NC-AFM is potentially the only technique capable of directly resolving the 3D angular arrangement of the individual adsorbed molecule and by evaluating consecutively acquired constant height force maps, we were able to directly measure the 3D structure and tilt of small TTPO and Pentacene-Quinone byproduct assemblies on Au (111). The molecule tilt was evaluated to 11±1°.