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Working Group "Physical Chemistry and Nanotechnology of Interfaces" (Prof. Kautek)

The working group "Physical Chemistry and Nanotechnology of Interfaces" (Prof. Kautek and coworkers) relies on pioneering work for more than 15 years in demonstrating femtosecond machining of a broad variety of materials soon after fs-laser got available in the early nineties
[W. Kautek and J. Krüger, SPIE Proceedings Vol. 2207, (1994), 600. "Femtosecond Pulse Laser Ablation of Metallic, Semiconducting, Ceramic and Biological Materials"].

Experience exists in top-down femtosecond laser ablation allowing micro- and nanomachining of 1D, 2D, and 3D structures in metals, transparent solids and biological tissues that cannot be made any other way. A special advantage is the unique possibility of congruent machining of highly inhomogeneous composite materials.

A new mechanism for ultrahigh machining precision has been proposed
[W. Kautek, J: Krüger, M. Lenzner, S. Sartania, C. Spielmann, and F. Krausz, Appl. Phys. Lett. 69 (1996) 3146.
M. Lenzner, J. Krüger, W. Kautek, F. Krausz, Appl. Phys. A 68 (1999) 369.
M. Lenzner, J. Krüger, S. Sartania, Z. Cheng, C. Spielmann, G. Mourou, W. Kautek, and F. Krausz, Phys. Rev. Lett. 80 (1998) 4076].
Pulse durations (<80 fs) far below the electron-phonon relaxation time in solids (>1 fs) provide the unique possibility to deterministically excite the electronic system by multi photon excitation resulting in unique precision in contrast to "conventional" fs-laser applications (>100 fs) where stochastic avalanche processes result in poor ablation qualities.

A novel optical setup coupling sub-60 fs-pulses into a high precision microscope will allow ultrahigh-precision processing. fs-pulses are necessary to avoid large heat affected zones (> 1µm) common with conventional ns-pulse lasers. Such non-linear phenomena can be exploited to reach supercritical intensities only in the focus of transparent bulk materials enabling laser direct-writing of 3D devices containing optical and microfluidic networks. This new approach to set up nano and microstructures can be applied to almost any transparent composite and functional material.

It was recently demonstrated that fs-laser-induced self assembly of nanostructures on solids opens a new approach to nano-structure surfaces bottom-up
[W. Kautek, P. Rudolph, G. Daminelli, J. Krüger, Appl. Phys. A 81 (2005) 65].
Non-thermal melting mechanisms play a decisive role together with the control of the surface energy.

Fs-Laser ablation of solids in liquid contact can be a process for synthesizing nanoparticles and nanotubes/nanorods
[G. Daminelli, J. Krüger, and W. Kautek, Thin Solid Films, 467 (2004) 334].
Thus uniformly small particles precipitate in solution. Fs-Pulsed laser deposition can serve to transfer delicate polymeric and biopolymeric materials to any substrate (fs-Laser Induced Forward Transfer, fs-LIFT) as a microprinting process avoiding thermal damage in sharp contrast to conventional nanosecond technology in LIFT.

Electrochemical scanning force microscopy allows to investigate the molecular structure of double layers and nanomanipulate electrified interfaces
[W. Kautek, S. Dieluweit, and M. Sahre, J. Phys. Chem. 101 (1997) 2709.
T. Solomun, W. Kautek, Electrochim. Acta 47 (2001) 679-687.].

Longterm experience exists in in-situ external reflection FT-IR Spectroscopy
[G.L.J. Trettenhahn, G.E. Nauer, A. Neckel, Electrochim. Acta 41 (1996) 1435.
W. Kautek, M. Geuß, M. Sahre, P. Zhao, S. Mirwald, Surf. Interface Anal. 25 (1997) 548.
W. Kautek, A. Conradi, Ch. Fabjan, G. Bauer, Electrochim. Acta 47 (2001) 815-823].

Biolectrochemistry could be demonstrated on crystalline single layer proteins on electrodes in a longterm collaboration with the Vienna University of Natural Resources and Applied Life Sciences (BOKU)
[M Handrea, M. Sahre, A. Neubauer, U.B. Sleytr, and W. Kautek, Bioelectrochemistry, 61 (2003) 1-8.
S. Dieluweit, D. Pum, U.B. Sleytr; W. Kautek, Materials Science and Engineering C 25 (2005) 727-732].

Institut für Physikalische Chemie
Universität Wien

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