Siles Pablo F, Devarajulu Mirunalini, Zhu Feng, Schmidt Oliver G
Materials Systems for Nanoelectronics, Chemnitz University of Technology, 09107, Chemnitz, Germany.
Institute for Integrative Nanosciences, IFW Dresden, 01069, Dresden, Germany.
Small. 2018 Mar;14(12):e1703647. doi: 10.1002/smll.201703647. Epub 2018 Feb 16.
The tailoring of organic systems is crucial to further extend the efficiency of charge transfer mechanisms and represents a cornerstone for molecular device technologies. However, this demands control of electrical properties and understanding of the physics behind organic interfaces. Here, a quantitative spatial overview of work function characteristics for phthalocyanine architectures on Au substrates is provided via kelvin probe microscopy. While macroscopic investigations are very informative, the current approach offers a nanoscale spatial rendering of electrical characteristics which is not possible to attain via conventional techniques. Interface dipole is observed due to the formation of charge accumulation layers in thin F CuPc, F CoPc, and MnPc films, displaying work functions of 5.7, 6.1, and 5.0 eV, respectively. The imaging and quantification of interface locations with significant surface potential and work function response (<0.33 eV for material thickness <1 nm) show also a dependency on the crystalline state of the organic systems. The work function mapping suggests space-charge carrier regions of about 4 nm at the organic interface. This reveals rich spatial electric parameters and ambipolar characteristics that may drive electrical performance at device scales, opening a realm of possibilities toward the development of functional organic architectures and its applications.
