Jonas Baumann

As nanostructures in the semiconductor industry become smaller and more complex, non-destructive characterization methods capable of measuring buried domains become crucial. Grazing emission x-ray fluorescence (GEXRF) spectroscopy is a measurement technique capable of resolving nanometer-sized features of buried nanostructures while providing information about the sample’s elemental distribution. In this work, a study was conducted to realistically assess the uncertainties of this method, considering correlations between geometric parameters. Furthermore, we showed strategies to effectively reduce the measurement time in GEXRF experiments by applying state-of-the-art single photon evaluation and machine learning denoising techniques for two-dimensional detectors. The study was performed on two different sample positions on a HfO₂/TiO₂ nanograting, where the GEXRF method was able to resolve geometric differences between them. Based on a finite element method model of the nanograting, the expected fluorescence intensities can be simulated, from which the nanostructure’s geometry can be reconstructed. The reconstructed geometric shapes show good agreement with atomic force microscope and transmission electron microscope measurements, highlighting the method’s capability for investigating samples within the nanometer regime.

Validation of simultaneous multi-angle AR-XANES proved the method successful in differentiating between chemical species in nanolayered structures. Applied to trace gold species in gilded wall painting replica after conservation with a new material.

Fire‐gilding is a historic technique for the application of golden layers on a number of different base materials utilizing a gold amalgam. This technique leaves a significant amount of Hg in the golden layer, giving archeometrists a reliable indicator to identify fire‐gildings. Recent findings on presumably fire‐gilded objects have shown in several cases significantly lower Hg content than previously studied objects. This prompted a synchrotron‐based X‐ray fluorescence investigation into the Hg distribution along the material–gilding interface, as well as a series of measurements regarding the Hg content development in fire‐gilded samples during artificial aging. This work presents findings on laboratory‐prepared fire‐gildings, indicating an Hg enrichment at the interface of fire‐gilded silver samples. Notably, such an enrichment is missing in fire‐gilded copper samples. Further, it is confirmed that fire‐gilded layers typically do not undercut an Hg bulk content of 5%. In this light, it seems improbable that ancient samples that contain <5% Hg are fire‐gilded. The results presented in this study might lead to a non‐destructive method to identify the Hg enrichment at the interface. This might be obtained by a combination of different non‐destructive measurements and might also work unambiguously in samples in which the gold top layer is altered.

Trace elements, functionalized nanoparticles and labeled entities can be localized with sub-mm spatial resolution by X-ray fluorescence imaging (XFI). Here, small animals are raster scanned with a pencil-like synchrotron beam of high energy and low divergence and the X-ray fluorescence is recorded with an energy-dispersive detector. The ability to first perform coarse scans to identify regions of interest, followed by a close-up with a sub-mm X-ray beam is desirable, because overall measurement time and X-ray dose absorbed by the (biological) specimen can thus be minimized. However, the size of X-ray beams at synchrotron beamlines is usually strongly dependent on the actual beamline setup and can only be adapted within specific pre-defined limits. Especially, large synchrotron beams are non-trivial to generate. Here, we present the concept of graphite-based, convex reflection optics for the one-dimensional enlargement of a 1 mm wide synchrotron beam by a factor of 5 to 10 within a 1 m distance. Four different optics are tested and characterized and their reflection properties compared to ray tracing simulations. The general shape and size of the measured reflection profiles agree with expectations. Enhancements with respect to homogeneity and efficiency can be expected with improved optics manufacturing. A mouse phantom is used for a proof-of-principle XFI experiment demonstrating the applicability of coarse and fine scans with the suggested optics design.

Angle‐resolved X‐ray fluorescence spectroscopy gives access to elemental analysis of nanoscaled materials. The two main techniques of this method are grazing incidence X‐ray fluorescence (GIXRF) and grazing emission X‐ray fluorescence (GEXRF) spectroscopy. Principles of both techniques including main applications are discussed in this Review. The main focus lies on the description of GEXRF technique and its new analytical possibilities in the nano‐world.

The development of thin-film thermoelectric applications in sensing and energy harvesting can benefit largely from suitable deposition methods for earth-abundant materials. In this study, p-type copper oxide thin films have been prepared on soda lime silicate glass by direct current (DC) magnetron sputtering at room temperature from a pure copper metallic target in an argon atmosphere, followed by subsequent annealing steps at 300 °C under various atmospheres, namely air (CuO:air), nitrogen (CuO:N) and oxygen (CuO:O). The resultant films have been studied to understand the influence of various annealing atmospheres on the structural, spectroscopic and thermoelectric properties. X-ray diffraction (XRD) patterns of the films showed reflexes that could be assigned to those of crystalline CuO with a thin mixed Cu^(I)Cu^(II) oxide, which was also observed by near edge X-ray absorption fine structure spectroscopy (NEXAFS). The positive Seebeck coefficient (S) reached values of up to 204 μV K⁻¹, confirming the p-type behavior of the films. Annealing under oxygen provided a significant improvement in the electrical conductivity up to 50 S m⁻¹, resulting in a power factor of 2 μW m⁻¹ K⁻². The results reveal the interplay between the intrinsic composition and the thermoelectric performance of mixed copper oxide thin films, which can be finely adjusted by simply varying the annealing atmosphere.

Efficient soft X-ray spectroscopy in the laboratory is still a challenging task. Here, we report on new toroidal multilayer optics designed and applied with the laser-produced plasma (LPP) source of the Berlin Laboratory for innovative X-ray technologies. The optics are described and characterized, and the application of the updated source to scanning-free grazing emission X-ray fluorescence is demonstrated on thermoelectric gold-doped copper oxide nanofilms. The comparison with synchrotron measurements allows estimating a flux on the sample of approximately 7.5 × 10⁹ photons/s in the 1 keV range on a 100 µm × 100 µm spot, emphasizing the suitability of the updated LPP source for the application in photon hungry experiments.

This work reports laboratory angle resolved XRF measurements with the goal of establishing laboratory techniques to obtain a more complete idea of the intralayer composition of multilayer samples.