TY  - THES
A1  - Morawetz, Knut
T1  - Untersuchungen zum Adsorptionsverhalten von gegenionen an Langmuir - Filmen
Y1  - 2001
ER  - 
TY  - JOUR
A1  - Stiller, Burkhard
A1  - Karageorgiev, Peter
A1  - Geue, Thomas
A1  - Morawetz, Knut
A1  - Saphiannikova, Marina
A1  - Mechau, Norman
A1  - Neher, Dieter
T1  - Optically induced mass transport studied by scanning near-field optical- and atomic force microscopy
N2  - Some functionalised thin organic films show a very unusual property, namely the light induced material transport. This effect enables to generate three-dimensional structures on surfaces of azobenzene containing films only caused by special optical excitation. The physical mechanisms underlying this phenomenon have not yet been fully understood, and in addition, the dimensions of structures created in that way are macroscopic because of the optical techniques and the wavelength of the used light. In order to gain deeper insight into the physical fundamentals of this phenomenon and to open possibilities for applications it is necessary to create and study structures not only in a macroscopic but also in nanometer range. We first report about experiments to generate optically induced nano structures even down to 100 nm size. The optical stimulation was therefore made by a Scanning Near-field Optical Microscope (SNOM). Secondly, physical conditions inside optically generated surface relief gratings were studied by measuring mechanical properties with high lateral resolution via pulse force mode and force distance curves of an AFM
Y1  - 2004
SN  - 0204-3467
ER  - 
TY  - JOUR
A1  - Saphiannikova, Marina
A1  - Geue, Thomas
A1  - Henneberg, Oliver
A1  - Morawetz, Knut
A1  - Pietsch, Ullrich
T1  - Linear viscoelastic analysis of formation and relaxation of azobenzene polymer gratings
N2  - Surface relief gratings on azobenzene containing polymer films were prepared under irradiation by actinic light. Finite element modeling of the inscription process was carried out using linear viscoelastic analysis. It was assumed that under illumination the polymer film undergoes considerable plastification, which reduces its original Young's modulus by at least three orders of magnitude. Force densities of about 10(11) N/m(3) were necessary to reproduce the growth of the surface relief grating. It was shown that at large deformations the force of surface tension becomes comparable to the inscription force and therefore plays an essential role in the retardation of the inscription process. In addition to surface profiling the gradual development of an accompanying density grating was predicted for the regime of continuous exposure. Surface grating development under pulselike exposure cannot be explained in the frame of an incompressible fluid model. However, it was easily reproduced using the viscoelastic model with finite compressibility. (C) 2004 American Institute of Physics
Y1  - 2004
U6  - https://doi.org/10.1063/1.1642606
ER  - 
TY  - JOUR
A1  - Stiller, Burkhard
A1  - Geue, Thomas
A1  - Morawetz, Knut
A1  - Saphiannikova, Marina
T1  - Optical patterning in azobenzene polymer films
N2  - Thin azobenzene polymer films show a very unusual property, namely optically induced material transport. The underlying physics for this phenomenon has not yet been thoroughly explained. Nevertheless, this effect enables one to inscribe different patterns onto film surfaces, including one- and two-dimensional periodic structures. Typical sizes of such structures are of the order of micrometers, i.e. related to the interference pattern made by the laser used for optical excitation. In this study we have measured the mechanical properties of one- and two-dimensional gratings, with a high lateral resolution, using force-distance curves and pulse force mode of the atomic force microscope. We also report on the generation of considerably finer structures, with a typical size of 100 nm, which were inscribed onto the polymer surface by the tip of a scanning near-field optical microscope used as an optical pen. Such inscription not only opens new application possibilities but also gives deeper insight into the fundamentals physics underlying optically induced material transport
Y1  - 2005
SN  - 0022-2720
ER  -