Sub-wavelength patterning of self-assembled organic monolayers via non-collinear optical parametric amplifier

Abstract

Self-assembled monolayers (SAMs) are ultra-thin organic monolayers, which can be used in different ways to assemble functionalized surface structures. This potential is caused by the ability of the SAMs to tie further molecules and components through the terminal groups of the organic layers. Additional applications for microfluidics and micromechanics require micro and nano structuring of the SAMs. In combination with multi-photon lithography (MPL) SAMs are offering advantageous properties as ultra thin layers. Thus, the processing with single pulses is feasible and results in very short processing times without the appearance of bubbles and formation of particles compared to photo resists. For our experiments, we used a non-collinear optical parametric amplifier (NOPA) which has the ability to generate short pulses of sub-30fs in the visible and near-infrared (NIR) range of light. The NOPA can be tuned in the range of 480 nm to 950 nm without spectral gaps.We used thiol based SAMs as ultra thin layers on gold substrates. The selected laser power offers the possibility of ablation of the SAMs without damaging the gold layer. Thereby we investigate the characteristics of thiol-based SAMs as monomolecular resists during etching of gold. We also investigate the wavelength dependencies of the substrate to get an optimal process window for the ablation process. Minimum structure sizes at a 1/e laser spot diameter of about 1.6 µm are close to 1/5 of the spot diameter.Self-assembled monolayers (SAMs) are ultra-thin organic monolayers, which can be used in different ways to assemble functionalized surface structures. This potential is caused by the ability of the SAMs to tie further molecules and components through the terminal groups of the organic layers. Additional applications for microfluidics and micromechanics require micro and nano structuring of the SAMs. In combination with multi-photon lithography (MPL) SAMs are offering advantageous properties as ultra thin layers. Thus, the processing with single pulses is feasible and results in very short processing times without the appearance of bubbles and formation of particles compared to photo resists. For our experiments, we used a non-collinear optical parametric amplifier (NOPA) which has the ability to generate short pulses of sub-30fs in the visible and near-infrared (NIR) range of light. The NOPA can be tuned in the range of 480 nm to 950 nm without spectral gaps.We used thiol based SAMs as ultra thin layers o...