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Type: Article × Subject: Carrier transport ×

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Now showing 1 - 3 of 3
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    A comprehensive study of charge transport in Au-contacted graphene on Ge/Si(001)
    (Melville, NY : American Inst. of Physics, 2020) Sinterhauf, Anna; Bode, Simeon; Auge, Manuel; Lukosius, Mindaugas; Lippert, Gunther; Hofsäss, Hans-Christian; Wenderoth, Martin
    We investigate the electronic transport properties of Au-contacted graphene on Ge/Si(001). Kelvin probe force microscopy at room temperature with an additionally applied electric transport field is used to gain a comprehensive understanding of macroscopic transport measurements. In particular, we analyze the contact pads including the transition region, perform local transport measurements in pristine graphene/Germanium, and explore the role of the semiconducting Germanium substrate. We connect the results from these local scale measurements with the macroscopic performance of the device. We find that a graphene sheet on a 2 μm Ge film carries approximately 10% of the current flowing through the device. Moreover, we show that an electronic transition region forms directly adjacent to the contact pads. This transition region is characterized by a width of >100 μm and a strongly increased sheet resistance acting as the bottleneck for charge transport. Based on Rutherford backscattering of the contact pads, we suggest that the formation of this transition region is caused by diffusion. © 2020 Author(s).
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    Donor-acceptor covalent organic frameworks for visible light induced free radical polymerization
    (Cambridge : RSC, 2019) Pachfule, Pradip; Acharjya, Amitava; Roeser, Jérôme; Sivasankaran, Ramesh P.; Ye, Meng-Yang; Brückner, Angelika; Schmidt, Johannes; Thomas, Arne
    Covalent organic frameworks (COFs) are promising materials for applications in photocatalysis, due to their conjugated, porous and chemically stable architectures. Alternating electron donor-acceptor-type structures are known to enhance charge carrier transport mobility and stability in polymers and are therefore also interesting building units for COFs used as photocatalysts but also as photoinitiator. In this work, two donor-acceptor COFs using electron deficient 4,4′,4′′-(1,3,5-triazine-2,4,6-triyl)trianiline and electron rich thiophene-based thieno[3,2-b]thiophene-2,5-dicarbaldehyde or [2,2′-bithiophene]-5,5′-dicarbaldehyde linkers are presented. The resulting crystalline and porous COFs have been applied as photoinitiator for visible light induced free radical polymerization of methyl methacrylate (MMA) to poly-methyl methacrylate (PMMA). These results pave the way to the development of robust and heterogeneous systems for photochemistry that offers the transfer of radicals induced by visible light. © The Royal Society of Chemistry 2019.
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    Kinetic Control over Self-Assembly of Semiconductor Nanoplatelets
    (Washington, DC : American Chemical Society, 2020) Momper, R.; Zhang, H.; Chen, S.; Halim, H.; Johannes, E.; Yordanov, S.; Braga, D.; Blülle, B.; Doblas, D.; Kraus, T.; Kraus, T.; Bonn, M.; Wang, H.I.; Riedinger, A.
    Semiconductor nanoplatelets exhibit spectrally pure, directional fluorescence. To make polarized light emission accessible and the charge transport effective, nanoplatelets have to be collectively oriented in the solid state. We discovered that the collective nanoplatelets orientation in monolayers can be controlled kinetically by exploiting the solvent evaporation rate in self-assembly at liquid interfaces. Our method avoids insulating additives such as surfactants, making it ideally suited for optoelectronics. The monolayer films with controlled nanoplatelets orientation (edge-up or face-down) exhibit long-range ordering of transition dipole moments and macroscopically polarized light emission. Furthermore, we unveil that the substantial in-plane electronic coupling between nanoplatelets enables charge transport through a single nanoplatelets monolayer, with an efficiency that strongly depends on the orientation of the nanoplatelets. The ability to kinetically control the assembly of nanoplatelets into ordered monolayers with tunable optical and electronic properties paves the way for new applications in optoelectronic devices.