Speaker
Description
Organic semiconductor crystals are often characterized by a strong anisotropy in their electrical and optical properties. In addition, vapor deposition of rod-like molecules often yield epitaxially grown crystallites with extreme length to width ratio. These kinds of wires are interesting candidates for functional components in organic electronics. Especially the conjunction of organic semiconductors with layered ultra-thin van der Waals (vdW) substrates has attracted interest as they might be composed into novel hybrid devices. Thus, it is essential to explore the shape, structure, and optoelectronic properties of such organic crystals grown epitaxially grown on vdW-substrates.
Here, we investigated crystalline dihydrotetraazaheptacene (DHTA7) needles epitaxially grown on ultrathin hexagonal boron nitride as a model system. [1] Its properties were studied utilizing electrostatic force microscopy together with a polarized light source. The specific resistivity of the DHTA7 needles changed by two orders of magnitude upon light exposure. Even charge propagation restricted to certain needle directions was achieved by matching the light’s polarization direction with the orientation of the molecular long axes. This way, charge could by “guided” to propagate along desired paths in self-assembled crystallite networks. Hence, we demonstrated that conductive paths can be switched on and off just by modulating the light’s polarization direction.
[1] A. Matković et al. Adv. Func. Mater. 29, 1903816 (2019).
| Speaker Country | Austria |
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