Direct Imaging of Space‐Charge Accumulation and Work Function Characteristics of Functional Organic Interfaces. Issue 12 (16th February 2018)

• Record Type: Journal Article
• Authors: Siles, Pablo F.; Devarajulu, Mirunalini; Zhu, Feng; Schmidt, Oliver G.
• Is Part Of: Small. Volume 14:Issue 12(2018)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2018-02-16
• Subjects: functional organic heterostructures -- interface surface potential -- nanoscale imaging -- scanning kelvin probe microscopy -- work function mapping; Nanotechnology -- Periodicals; Nanoparticles -- Periodicals; Microtechnology -- Periodicals; 620.5
• DOI: 10.1002/smll.201703647
• Languages: English
• ISSNs: 1613-6810

Abstract

Abstract: 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 F16 CuPc, F16 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. Abstract : A complete nanoscale view of surface potential characteristics and a quantitative overview of work function and energy‐level alignment are observed at the interface of functional organic junctions via kelvin probe microscopy approaches. The results open interesting physical perspectives enabling straightforward correlation between morphology and high‐resolution quantification of important electric parameters revealing details like ambipolar characteristics and interface space‐charge carrier regions.