@article{KuehnPingelBreusingetal.2011,
  author    = {Kuehn, Sergei and Pingel, Patrick and Breusing, Markus and Fischer, Thomas and Stumpe, Joachim and Neher, Dieter and Elsaesser, Thomas},
  title     = {High-Resolution Near-Field Optical Investigation of Crystalline Domains in Oligomeric PQT-12 Thin Films},
  series = {Advanced functional materials},
  volume    = {21},
  journal   = {Advanced functional materials},
  number    = {5},
  publisher = {Wiley-Blackwell},
  address   = {Malden},
  issn      = {1616-301X},
  doi       = {10.1002/adfm.201001978},
  pages     = {860 -- 868},
  year      = {2011},
  abstract  = {The structure and morphology on different length scales dictate both the electrical and optical properties of organic semiconductor thin films. Using a combination of spectroscopic methods, including scanning near-field optical microscopy, we study the domain structure and packing quality of highly crystalline thin films of oligomeric PQT-12 with 100 nanometer spatial resolution. The pronounced optical anisotropy of these layers measured by polarized light microscopy facilitates the identification of regions with uniform molecular orientation. We find that a hierarchical order on three different length scales exists in these layers, made up of distinct well-ordered dichroic areas at the ten-micrometer-scale, which are sub-divided into domains with different molecular in-plane orientation. These serve as a template for the formation of smaller needle-like crystallites at the layer surface. A high degree of crystalline order is believed to be the cause of the rather high field-effect mobility of these layers of 10(-3) cm 2 V(-1) s(-1), whereas it is limited by the presence of domain boundaries at macroscopic distances.},
  language  = {en}
}
@article{ZamponiAnsarivonKorffSchmisingetal.2009,
  author    = {Zamponi, Flavio and Ansari, Zunaira and von Korff Schmising, Clemens and Rothhardt, Philip and Zhavoronkov, Nickolai and Woerner, Michael and Elsaesser, Thomas and Bargheer, Matias and Trobitzsch-Ryll, Timo and Haschke, Michael},
  title     = {Femtosecond hard X-ray plasma sources with a kilohertz repetition rate},
  issn      = {0947-8396},
  doi       = {10.1007/s00339-009-5171-9},
  year      = {2009},
  abstract  = {Laser-driven plasma sources of femtosecond hard X-ray pulses have found widespread application in ultrafast X- ray diffraction. The recent development of plasma sources working at kilohertz repetition rates has allowed for diffraction experiments with strongly improved sensitivity, now revealing subtle fully reversible changes of the geometry of crystal lattices. We provide a brief review of this development and present a novel plasma source with an optimized mechanical and optical design, providing a high flux of several 10(10) photons/s at the Cu-K alpha energy of 8.04 keV and a pulse duration of a parts per thousand currency sign300 fs. First experiments, including the generation of Debye-Scherrer diffraction patterns from Si powder, demonstrate the high performance of this source.},
  language  = {en}
}
@article{WoernervonKorffSchmisingBargheeretal.2009,
  author    = {Woerner, Michael and von Korff Schmising, Clemens and Bargheer, Matias and Zhavoronkov, Nickolai and Vrejoiu, Ionela and Hesse, Dietrich and Alexe, Marin and Elsaesser, Thomas},
  title     = {Ultrafast structural dynamics of perovskite superlattices},
  issn      = {0947-8396},
  doi       = {10.1007/s00339-009-5174-6},
  year      = {2009},
  abstract  = {Femtosecond x-ray diffraction provides direct insight into the ultrafast reversible lattice dynamics of materials with a perovskite structure. Superlattice (SL) structures consisting of a sequence of nanometer-thick layer pairs allow for optically inducing a tailored stress profile that drives the lattice motions and for limiting the influence of strain propagation on the observed dynamics. We demonstrate this concept in a series of diffraction experiments with femtosecond time resolution, giving detailed information on the ultrafast lattice dynamics of ferroelectric and ferromagnetic superlattices. Anharmonically coupled lattice motions in a SrRuO3/PbZr0.2Ti0.8O3 (SRO/ PZT) SL lead to a switch-off of the electric polarizations on a time scale of the order of 1 ps. Ultrafast magnetostriction of photoexcited SRO layers is demonstrated in a SRO/SrTiO3 (STO) SL.},
  language  = {en}
}