TY - JOUR A1 - König, Tobias A1 - Papke, Thomas A1 - Kopyshev, Alexey A1 - Santer, Svetlana T1 - Atomic force microscopy nanolithography fabrication of metallic nano-slits using silicon nitride tips JF - Journal of materials science N2 - In this paper, we report on the properties of nano-slits created in metal thin films using atomic force microscope (AFM) nanolithography (AFM-NL). We demonstrate that instead of expensive diamond AFM tips, it is also possible to use low cost silicon nitride tips. It is shown that depending on the direction of scratching, nano-slits of different widths and depths can be fabricated at constant load force. We elucidate the reasons for this behavior and identify an optimal direction and load force for scratching a gold layer. Y1 - 2013 U6 - https://doi.org/10.1007/s10853-013-7188-x SN - 0022-2461 VL - 48 IS - 10 SP - 3863 EP - 3869 PB - Springer CY - New York ER - TY - JOUR A1 - König, Tobias A1 - Santer, Svetlana T1 - Visualization of surface plasmon interference by imprinting intensity patterns on a photosensitive polymer JF - Nanotechnology N2 - We report on sub-wavelength structuring of photosensitive azo-containing polymer films induced by a surface plasmon interference intensity pattern. The two surface plasmon waves generated at neighboring nano-slits in the metal layer during irradiation interfere constructively, resulting in an intensity pattern with a periodicity three times smaller than the wavelength of the incoming light. The near field pattern interacts with the photosensitive polymer film placed above it, leading to a topography change which follows the intensity pattern exactly, resulting in the formation of surface relief gratings of a size below the diffraction limit. We analyze numerically and experimentally how the depth of the nano-slit alters the interference pattern of surface plasmons and find that the sub-wavelength patterning of the polymer surface could be optimized by modifying the geometry and the size of the nano-slit. Y1 - 2012 U6 - https://doi.org/10.1088/0957-4484/23/48/485304 SN - 0957-4484 VL - 23 IS - 48 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - König, Tobias A1 - Santer, Svetlana T1 - Stretching and distortion of a photosensitive polymer film by surface plasmon generated near fields in the vicinity of a nanometer sized metal pin hole JF - Nanotechnology N2 - Here we demonstrate how a surface plasmon (SP) generated near field pattern in the vicinity of a nano-scale pin hole can be used to generate reversible topography changes in a photosensitive polymer film above the opening. This can be achieved by simply changing the polarization state of the plasmon generating incoming light. In the case of linear polarization, the near field intensity pattern causes the film to laterally expand/contract according to the direction of the polarization. For circular polarization, two pronounced rims corresponding to maxima in the topography are observed. In all cases, the topographical variation is in close agreement with the SP intensity distribution computed from finite difference time domain simulation. Our results demonstrate the versatility of using SP near fields to imprint a variety of structures into photosensitive polymer films using only a single metallic mask. Y1 - 2012 U6 - https://doi.org/10.1088/0957-4484/23/15/155301 SN - 0957-4484 VL - 23 IS - 15 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - König, Tobias A1 - Sekhar, Y. Nataraja A1 - Santer, Svetlana T1 - Surface plasmon nanolithography impact of dynamically varying near-field boundary conditions at the air-polymer interface JF - Journal of materials chemistry N2 - It is well-known that surface plasmon generated near fields of suitably irradiated metal nano-structures can induce a patterning in an azobenzene-modified photosensitive polymer film placed on top. The change in the topography usually follows closely and permanently the underlying near field intensity pattern. With this approach, one can achieve a multitude of morphologies by additionally changing light intensity, polarization and the kind of metal used for nano-structuring. In this paper, we demonstrate that below a critical value of the polymer film thickness, the receding polymer material induces a change in refractive index of the glass-metal-polymer system, modifying the near field intensity distribution and causing a back-reaction on the flow of polymer material. This has a profound influence on the smallest size of topographical features that can be imprinted into the polymer. Y1 - 2012 U6 - https://doi.org/10.1039/c2jm15864g SN - 0959-9428 VL - 22 IS - 13 SP - 5945 EP - 5950 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - König, Tobias A1 - Yadavalli, Nataraja Sekhar A1 - Santer, Svetlana T1 - Near-Field induced reversible structuring of photosensitive polymer films Gold versus silver nano-antennas JF - Plasmonics N2 - We report on reversible structuring of photosensitive azo-containing polymer films induced by near-field intensity patterns emanating from illuminated nano-scale metal structures fabricated by colloidal lithography. Two different sets of these nano-antennas, consisting of either gold or silver, were investigated with respect to their ability to induce topography changes in a photosensitive polymer film placed above. Using in situ recorded atomic force microscopy micrographs of polymer topography changes during UV irradiation, we find that the response of the polymer film differs for the two metals at similar geometries of the metal nanostructures. The maximum topography change is stronger for Ag antennas as compared to the Au pattern, whereas the latter material revealed a pronounced splitting of topography maxima into two, a phenomenon less visible in the case of Ag. Finite difference time domain simulations of the electromagnetic field distribution in the vicinity of the metal structures confirm this remarkable observation. The local intensity is twice as large for the Ag as compared to the Au structures, and in each case, a splitting of the intensity pattern results, with a stronger modulation for Au. For both metals, the topography change was found to be reversible between a patterned and a flat by repeated change of irradiation conditions. KW - Photosensitive polymer films KW - Surface plasmons Y1 - 2012 U6 - https://doi.org/10.1007/s11468-012-9339-3 SN - 1557-1955 VL - 7 IS - 3 SP - 535 EP - 542 PB - Springer CY - New York ER - TY - JOUR A1 - Yadavalli, Nataraja Sekhar A1 - König, Tobias A1 - Santer, Svetlana T1 - Selective mass transport of azobenzene-containing photosensitive films towards or away from the light intensity JF - Journal of the Society for Information Display N2 - Here, we report on two photosensitive amorphous polymers showing opposite behavior upon exposure to illumination. The first polymer (PAZO) consists of linear backbone to which azobenzene-containing side chains are covalently attached, while in the second polymer (azo-PEI), the azobenzene side chains are attached ionically to a polyelectrolyte backbone. When irradiated through a mask, the PAZO goes away from the intensity maxima, leaving behind topography trenches, while the direction of the mass transport of the azo-PEI polymer points towards the intensity maxima. This kind of behavior has been reported only for certain liquid crystalline polymers that exhibit in-phase reaction on illumination, that is, topography maxima coincides with the intensity maxima. Furthermore, flat nanocrystals placed on top of azo-PEI film was found to be moved together with the mass transport of the underlying polymer film as visualized using in situ atomic force microscopy (AFM) measurements. It was also demonstrated that the two polymer films respond differently on irradiation with the polarization and intensity interference patterns (IPs). To record the kinetic of the surface relief grating formation within two polymers during irradiation with different IPs, we utilized a homemade setup combining the optical part for the generation of IP and AFM. A possible mechanism explaining different responses on the irradiation of amorphous polymers is discussed in the frame of a theoretical model proposed by Saphiannikova et al. (J. Phys. Chem. B 113, 5032-5045 (2009)). KW - azobenzene KW - surface relief grating KW - light-induced mass transport KW - interference pattern KW - nano-object motion Y1 - 2015 U6 - https://doi.org/10.1002/jsid.306 SN - 1071-0922 SN - 1938-3657 VL - 23 IS - 4 SP - 154 EP - 162 PB - Wiley-Blackwell CY - Hoboken ER -