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Organic semiconductors make cheap, flexible and environmentally friendly electronic devices which do not rely on doping by rare elements. Applications range from OLED displays and solar cells to e-Paper and logic or display circuitry embedded in everyday devices. The intrinsic electronic properties of the material and its interaction with contacting interfaces is important to understand and tune the device characteristics and functionality.
Pentacene and its chemical derivatives are not only the “small molecule” organic semiconductor with the highest intrinsic mobility, but also provide a model system to investigate local chemical and physical properties at surfaces. [2] It is remarkable, that single molecular layers can be operated and doped in thin film transistors (TFTs) [3-5] and that the molecular packing in the monolayer modifies the Shockley surface state in contacting metal substrates [6, 7]. Pyrazinacenes, on the other hand are a newly synthesized class of molecules which complement to p-type pentacene derivatives with their closely related molecular structure and their nitrogen (N) content. [1] We report on the supra-molecular interactions and self-assembly of octa-azatetracene and deca-azapentacenes, two different lengths molecules in this class. The compounds are imaged individually and form structurally related chains. Their oxidation on-surfaces is compared to the dehydrogenation in solution. Experimental evidence is provided by Scanning Tunneling Microscopy and X-ray Photoelectron Spectroscopy and temperature dependent transport experiments of planar thin film transistors with an active channel region of 1-3 molecular monolayers.

References
[1] D. Miklik, et al. Communications Chemistry 2021, 10.1038/s42004-021-00470-w
[2] K. Mueller et al., J. Phys Chem C, 116, 2012, 10.1021/jp308058u
[3] C. Vanoni, et al. Appl. Phys. Lett. 2009, 94, 253306. 10.1063/1.3159835
[4] C. Vanoni, et al. Appl. Phys. Lett. 2007, 90, 193119. 10.1063/1.2738382
[5] T. Hählen, et al., Appl. Phys. Lett. 2012, 101, 033305, 10.1063/1.4737214
[6] K. Mueller et al., Phys Rev. B 79, 245421, 2009, 10.1103/PhysRevB.79.245421
[7] A. Scheybal et al., Phys Rev. B 79, 115406, 2009, 10.1103/PhysRevB.79.115406