We present a compact setup for near-edge x-ray absorption spectroscopy at the carbon K-edge based on a laser-driven plasma source. To generate the required broad-band emission in the spectral range of the ‘water window’ (λ = 2.2–4.4 nm) a krypton gas puff target was used. The table-top setup consisting basically of the laser-plasma source and a flat-field spectrometer can be used for near-edge x-ray absorption fine structure experiments in transmission as well as reflection under grazing incidence conditions (ReflEXAFS). The latter method offers the advantage that thin film preparation is not necessary and that the surface sensitivity is strongly enhanced. The results obtained for thin polymer films show good agreement with synchrotron data. Furthermore, we use the ReflEXAFS method to investigate changes in the chemical composition of PMMA induced by extreme ultraviolet (EUV) radiation. The spectra indicate a loss of the carbonyl functional group upon irradiation as well as crosslinking effects at high EUV radiation doses.

In order to perform material interaction studies with intense extreme ultraviolet (EUV) radiation, a Schwarzschild mirror objective coated with Mo/Si multilayers was adapted to a compact laser-based EUV plasma source (pulse energy 3 mJ at λ=13.5 nm, plasma diameter ∼300 μm). By 10× demagnified imaging of the plasma a pulse energy density of ∼75 mJ∕cm2 at a pulse length of 6 ns can be achieved in the image plane of the objective. As demonstrated for poly(methyl methacrylate) (PMMA), photoetching of polymer surfaces is possible at this EUV fluence level. This paper presents first results, including a systematic determination of PMMA etching rates under EUV irradiation. Furthermore, the contribution of out-of-band radiation to the surface etching of PMMA was investigated by conducting a diffraction experiment for spectral discrimination from higher wavelength radiation. Imaging of a pinhole positioned behind the plasma accomplished the generation of an EUV spot of 1 μm diameter, which was employed for direct writing of surface structures in PMMA.

We present first damage threshold investigations on EUV mirrors and substrate materials using a table-top laser produced plasma source. A Schwarzschild objective with Mo/Si multilayer coatings for the wavelength of 13.5 nm was adapted to the source, generating an EUV spot of 5 microm diameter with a maximum energy density of approximately 6.6 J/cm(2). Single-pulse damage tests were performed on grazing incidence gold mirrors, Mo/Si multilayer mirrors and mirror substrates, respectively. For gold mirrors, a film thickness dependent damage threshold is observed, which can be partially explained by a thermal interaction process. For Mo/Si multilayer mirrors two damage regimes (spot-like, crater) were identified. Fused silica exhibits very smooth ablation craters, indicating a direct photon-induced bond breaking process. Silicon shows the highest damage threshold of all investigated substrate and coating materials. The damage experiments on substrates (fused silica, silicon, CaF(2)) were compared to excimer laser ablation studies at 157 nm.

Purpose We present the characterization of environmental samples using near-edge X-ray absorption fine structure (NEXAFS) spectra recorded with an in-house device. We want to point out the feasibility of such an easily accessed complementary technique, if not sometimes alternative to NEXAFS studies performed with synchrotron radiation, as the number of compact setups is increasing. Materials and methods The experiments were carried out using a laser-driven plasma source. We studied heterogeneous samples like refractory organic substances to demonstrate the potential of NEXAFS spectra, achieved by such an instrument, concerning specimens of high chemical complexity.Results and discussion From the respective resonance peaks in the spectra, the presence of certain functional groups, such as aromatic or carbonyl groups, is verified, and the elemental composition is estimated. The results of the reference samples are consistent with the literature. For the environmental samples, external influences of the extraction solvent or fertilizers can be determined from the spectra. Conclusions This could provide the possibility to perform test experiments with samples, which are later studied in more detail with synchrotron light and might as well give an impulse on the broader spread of the application of NEXAFS spectroscopy.

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