7 research outputs found

    Interference in edge-scattering from monocrystalline gold flakes

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    We observe strongly dissimilar scattering from two types of edges in hexagonal quasi-monocrystalline gold flakes with thicknesses around 1 micron. We identify as the origin the interference between a direct, quasi-specular scattering and an indirect scattering process involving an intermediate surface-plasmon state. The dissimilarity between the two types of edges is a direct consequence of the three-fold symmetry around the [111]-axis and the intrinsic chirality of a face-centered cubic lattice. We propose that this effect can be used to estimate flake thickness, crystal morphology, and surface contamination

    Structural basis for a naphthyl end-capped oligothiophene with embedded metallic nanoparticles for organic field-effect transistors

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    We report on the apparent structure of 5,5″-bis(naphth-2-yl)-2,2′:5′,2″-terthiophene (NaT3) in organic field-effect transistors (OFETs) with and without embedded silver nanoparticles. Using regular- and microbeam grazing incidence wide- and small-angle X-ray scattering, the device structure is characterized locally in the area with the embedded particles. The NaT3 thin film order is reduced and the found unit cell (a = 25.7 Å, b = 5.87 Å, c = 8.03 Å, and β = 98.9°) differs significantly from the one reported in the bulk, but shows no significant change, when the particles corresponding to the crystal size are incorporated into the device structure. At the same time, the apparent thin film crystal sizes in OFETs are found to be similar with and without the embedded particles. In both cases, the carrier mobilities are of the order of 104^{−4} cm2^2/(V s)

    Structural Evaluation of 5,5′-Bis(naphth-2-yl)-2,2′-bithiophene in Organic Field-Effect Transistors with <i>n</i>‑Octadecyltrichlorosilane Coated SiO<sub>2</sub> Gate Dielectric

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    We report on the structure and morphology of 5,5′-bis­(naphth-2-yl)-2,2′-bithiophene (NaT2) films in bottom-contact organic field-effect transistors (OFETs) with octadecyltrichlorosilane (OTS) coated SiO<sub>2</sub> gate dielectric, characterized by atomic force microscopy (AFM), grazing-incidence X-ray diffraction (GIXRD), and electrical transport measurements. Three types of devices were investigated with the NaT2 thin-film deposited either on (1) pristine SiO<sub>2</sub> (corresponding to higher surface energy, 47 mJ/m<sup>2</sup>) or on OTS deposited on SiO<sub>2</sub> under (2) anhydrous or (3) humid conditions (corresponding to lower surface energies, 20–25 mJ/m<sup>2</sup>). NaT2 films grown on pristine SiO<sub>2</sub> form nearly featureless three-dimensional islands. NaT2 films grown on OTS/SiO<sub>2</sub> deposited under anhydrous conditions form staggered pyramid islands where the interlayer spacing corresponds to the size of the NaT2 unit cell. At the same time, the grain size measured by AFM increases from hundreds of nanometers to micrometers and the crystal size measured by GIXRD from 30 nm to more than 100 nm. NaT2 on OTS/SiO<sub>2</sub> deposited under humid conditions also promotes staggered pyramids but with smaller crystals 30–80 nm. The NaT2 unit cell parameters in OFETs differ 1–2% from those in bulk. Carrier mobilities tend to be higher for NaT2 layers on SiO<sub>2</sub> (2–3 × 10<sup>–4</sup> cm<sup>2</sup>/(V s)) compared to NaT2 on OTS (2 × 10<sup>–5</sup>–1 × 10<sup>–4</sup> cm<sup>2</sup>/(V s)). An applied voltage does not influence the unit cell parameters when probed by GIXRD in operando