TY  - JOUR
A1  - Kuehn, Sergei
A1  - Pingel, Patrick
A1  - Breusing, Markus
A1  - Fischer, Thomas
A1  - Stumpe, Joachim
A1  - Neher, Dieter
A1  - Elsaesser, Thomas
T1  - High-Resolution Near-Field Optical Investigation of Crystalline Domains in Oligomeric PQT-12 Thin Films
JF  - Advanced functional materials
N2  - 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.
Y1  - 2011
U6  - https://doi.org/10.1002/adfm.201001978
SN  - 1616-301X
VL  - 21
IS  - 5
SP  - 860
EP  - 868
PB  - Wiley-Blackwell
CY  - Malden
ER  - 
TY  - JOUR
A1  - Kollosche, Matthias
A1  - Döring, Sebastian
A1  - Stumpe, Joachim
A1  - Kofod, Guggi
T1  - Voltage-controlled compression for period tuning of optical surface
 relief gratings
JF  - OPTICS LETTERS
N2  - This Letter reports on new methods and a consistent model for voltage tunable optical transmission gratings. Elastomeric gratings were molded from holographically written surface relief gratings in an azobenzene sol-gel material. These were placed on top of a transparent electroactive elastomeric substrate. Two different electro-active substrate elastomers were employed, with a large range of prestretches. A novel finite-deformation theory was found to match the device response excellently, without fitting parameters. The results clearly show that the grating underwent pure-shear deformation, and more surprisingly, that the mechanical properties of the electro-active substrate did not affect device actuation. (C) 2011 Optical Society of America
Y1  - 2011
SN  - 0146-9592
VL  - 36
IS  - 8
SP  - 1389
EP  - 1391
PB  - OPTICAL SOC AMER
CY  - WASHINGTON
ER  - 
TY  - JOUR
A1  - Koenig, Tobias
A1  - Goldenberg, Leonid M.
A1  - Kulikovska, Olga
A1  - Kulikovsky, Lazar
A1  - Stumpe, Joachim
A1  - Santer, Svetlana
T1  - Reversible structuring of photosensitive polymer films by surface plasmon near field radiation
JF  - Soft matter
N2  - We report on the fabrication and characterisation of a novel type of hybrid azo-modified photosensitive polymer film with a nanoscale metallic structuring integrated into the substrate. The metal structures permit to generate surface plasmon near fields when irradiated by UV-light from the rear without directly illuminating the polymer. This allows establishment of a localized, complex-shape intensity distribution at sub-wavelength resolution with a corresponding impact on the photosensitive polymer. The possibilities of exploiting this setup are manifold. We find that just by using the change of polarization of the incident light as means of control, the topography can be driven to change between various patterns reversibly. These results are confirmed by numerical simulations and compared with in situ recorded topography changes.
Y1  - 2011
U6  - https://doi.org/10.1039/c0sm01164a
SN  - 1744-683X
VL  - 7
IS  - 9
SP  - 4174
EP  - 4178
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Döring, Sebastian
A1  - Kollosche, Matthias
A1  - Rabe, Torsten
A1  - Stumpe, Joachim
A1  - Kofod, Guggi
T1  - Electrically tunable polymer DFB laser
JF  - Advanced materials
Y1  - 2011
U6  - https://doi.org/10.1002/adma.201102465
SN  - 0935-9648
VL  - 23
IS  - 37
SP  - 4265
EP  - 4269
PB  - Wiley-VCH
CY  - Weinheim
ER  -