Quantitative Measurement of the Near-Field Enhancement of Nanostructures by Two-Photon Polymerization
| Autor: | Hiroaki Misawa, Andreas Kolloch, Johannes Boneberg, Tobias Geldhauser, Kosei Ueno, Paul Leiderer, Naoki Murazawa, Elke Scheer |
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| Rok vydání: | 2012 |
| Předmět: |
Materials science
Nanostructure Polymers Surface Properties Near and far field Substrate (electronics) Fluence Polymerization law.invention Optics law Electrochemistry ddc:530 General Materials Science Laser power scaling Particle Size Spectroscopy Photons business.industry Finite-difference time-domain method Colloidal Nanoplasmonics Surfaces and Interfaces Condensed Matter Physics Laser Nanostructures Epoxy Compounds business Intensity (heat transfer) |
| Zdroj: | Langmuir. 28:9041-9046 |
| ISSN: | 1520-5827 0743-7463 |
| DOI: | 10.1021/la300219w |
| Popis: | The quantitative determination of the strength of the near-field enhancement in and around nanostructures is essential for optimizing and using these structures for applications. We combine the gaussian intensity distribution of a laser profile and two-photon-polymerization of SU-8 to a suitable tool for the quantitative experimental measurement of the near-field enhancement of a nanostructure. Our results give a feedback to the results obtained by finite-difference time-domain (FDTD) simulations. The structures under investigation are gold nanotriangles on a glass substrate with 85 nm side length and a thickness of 40 nm. We compare the threshold fluence for polymerization for areas of the gaussian intensity profile with and without the near-field enhancement of the nanostructures. The experimentally obtained value of the near-field intensity enhancement is 600 ± 140, independent of the laser power, irradiation time, and spot size. The FDTD simulation shows a pointlike maximum of 2600 at the tip. In a more extended area with an approximate size close to the smallest polymerized structure of 25 nm in diameter, we find a value between 800 and 600. Using our novel approach, we determine the threshold fluence for polymerization of the commercially available photopolymerizable resin SU-8 by a femtosecond laser working at a wavelength of 795 nm and a repetition rate of 82 MHz to be 0.25 J/cm(2) almost independent of the irradiation time and the laser power used. This finding is important for future applications of the method because it enables one to use varying laser systems. |
| Databáze: | OpenAIRE |
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