Overview of nanoscale NEXAFS performed with soft X-ray microscopes

Bittencourt, Carla

doi:10.3762/bjnano.6.61

Cited by 24 publications

(15 citation statements)

References 67 publications

(73 reference statements)

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“…But evidence for effective "bombardment-induced decomposition" (Kelly, 1989) and reduction can even be found in outer space. The low albedo of silicate rocks from the moon's surface was attributed to solar wind bombardment (Hapke, 1973), which causes an enrichment of nanoscale metallic iron particles in the near-surface layer of lunar regolith via a preferential sputtering mechanism, where oxygen is preferentially sputtered off, leaving the reduced bare metal behind (Betz and Wehner, 1983). Whether micrometeoroid impacts have a major contribution to this so-called lunar "space weathering" by (re)melting the surface layer of lunar soil grains or whether solar wind contributes more due to ion (H and He) implantation is still under discussion, however (Kuhlman et al, 2015;Pieters and Noble, 2016).…”

Section: Resultsmentioning

confidence: 99%

Response to referee Adam Hitchcock

Andreae¹

2019

Preprint

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The spatial distribution of transition metal valence states is of broad interest in the microanalysis of geological and environmental samples. An example is rock varnish, a natural manganese (Mn)-rich rock coating, whose genesis mechanism remains a subject of scientific debate. We conducted scanning transmission X-ray microscopy with nearedge X-ray absorption fine-structure spectroscopy (STXM-NEXAFS) measurements of the abundance and spatial distribution of different Mn oxidation states within the nanoto micrometer thick varnish crusts. Such microanalytical measurements of thin and hard rock crusts require sample preparation with minimal contamination risk. Focused ion beam (FIB) slicing was used to obtain ∼ 100-1000 nm thin wedge-shaped slices of the samples for STXM, using standard parameters. However, while this preparation is suitable for investigating element distributions and structures in rock samples, we observed artifactual modifications of the Mn oxidation states at the surfaces of the FIB slices. Our results suggest that the preparation causes a reduction of Mn 4+ to Mn 2+ . We draw attention to this issue, since FIB slicing, scanning electron microscopy (SEM) imaging, and other preparation and visualization techniques operating in the kilo-electron-volt range are well-established in geosciences, but researchers are often unaware of the potential for the reduction of Mn and possibly other elements in the samples.

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Section: Resultsmentioning

confidence: 99%

Response to referee Adam Hitchcock

Andreae¹

2019

Preprint

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“…In fullfield microscopes, e.g. transmission X-ray microscopes (TXM) (Kaulich et al, 2011;Guttmann & Bittencourt, 2015) and X-ray photoemission electron microscopes (X-PEEM) (Gü nther et al, 2002;Leung et al, 2010;Schofield et al, 2014), the whole field of view is directly imaged onto a detector plane so that a spatially resolved imaging detector, such as a CCD or a pixel-array detector, is required. On the other hand, with scanning microscopes, e.g.…”

Section: Introductionmentioning

confidence: 99%

Development of a scanning soft X-ray spectromicroscope to investigate local electronic structures on surfaces and interfaces of advanced materials under conditions ranging from low vacuum to helium atmosphere

Oura

Ishihara

Osawa

et al. 2020

J Synchrotron Radiat

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A scanning soft X-ray spectromicroscope was recently developed based mainly on the photon-in/photon-out measurement scheme for the investigation of local electronic structures on the surfaces and interfaces of advanced materials under conditions ranging from low vacuum to helium atmosphere. The apparatus was installed at the soft X-ray beamline (BL17SU) at SPring-8. The characteristic features of the apparatus are described in detail. The feasibility of this spectromicroscope was demonstrated using soft X-ray undulator radiation. Here, based on these results, element-specific two-dimensional mapping and micro-XAFS (X-ray absorption fine structure) measurements are reported, as well as the observation of magnetic domain structures from using a reference sample of permalloy micro-dot patterns fabricated on a silicon substrate, with modest spatial resolution (e.g. ∼500 nm). Then, the X-ray radiation dose for Nafion® near the fluorine K-edge is discussed as a typical example of material that is not radiation hardened against a focused X-ray beam, for near future experiments.

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“…Since synchrotron-based X-ray microscopes offer continuously tunable excitation photon energy, it has been shown that within a multilayer of several photoresists consecutively stacked at the same spot, each layer can be addressed separately by the resonant photon energy of the respective Following the development of suitable focusing optics for soft X-rays [49][50][51], the first soft X-ray microscopes were installed in the mid-1980s [52,53]. Since then, STXM has developed into a versatile method for characterization of suitably thin specimens from various scientific disciplines, such as biology, medicine, catalysis, material science, magnetism, geology, cosmology, and cultural heritage [54][55][56][57][58][59][60][61][62][63][64]. Figure 1 depicts a scheme of a modern STXM with all basic elements and their respective degrees of freedom [59,65,66].…”

Section: Introductionmentioning

confidence: 99%

Additive Nano-Lithography with Focused Soft X-rays: Basics, Challenges, and Opportunities

Späth

2019

Micromachines

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Focused soft X-ray beam induced deposition (FXBID) is a novel technique for direct-write nanofabrication of metallic nanostructures from metal organic precursor gases. It combines the established concepts of focused electron beam induced processing (FEBIP) and X-ray lithography (XRL). The present setup is based on a scanning transmission X-ray microscope (STXM) equipped with a gas flow cell to provide metal organic precursor molecules towards the intended deposition zone. Fundamentals of X-ray microscopy instrumentation and X-ray radiation chemistry relevant for FXBID development are presented in a comprehensive form. Recently published proof-of-concept studies on initial experiments on FXBID nanolithography are reviewed for an overview on current progress and proposed advances of nanofabrication performance. Potential applications and advantages of FXBID are discussed with respect to competing electron/ion based techniques. polymer resulting in 3D patterning by radiation chemistry [33,34]. The approach is limited to materials with significantly different absorption cross-sections at the chosen incident photon energies, as in transmission geometry, all layers are exposed to the beam at different degrees of focusing. However, such experiments open a completely novel perspective for complex direct-write nanofabrication. It should be mentioned that during the late 1980s and early 1990s several groups attempted to exploit broad-band synchrotron light [38][39][40][41] as well as the monochromatic X-ray beam of a photon-induced scanning Auger microscope [42,43] for additive manufacturing of metal deposits from metal organic precursors. However, due to limited instrumental capabilities, only spatially extended thin films with an optimum of some 10 µm resolution could be produced [43].FXBID exploits the photon energy-selectivity of synchrotron-based XRL and extends it by the idea of depositing metal nanostructures from suitable precursor gases [21,22]. The use of a STXM setup for these experiments offers several advantages. STXM is a raster-scanning technique which avoids the necessity of shadow masks. According to comparable results from polymer lithography the theoretical minimum feature size of the deposited metal structures is mainly determined by the spot size of the incident beam [36,37]. Recent developments in X-ray optics have pushed this parameter below 10 nm [44,45]. Finally, STXM can be employed for an in-situ analysis of the metallic deposits directly after fabrication by means of resonant imaging and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy to evaluate confinement, growth rates, oxidation state and chemical purity [21,22,46,47]. X-ray magnetic circular dichroism (XMCD) can be used to characterize magnetic deposits with respect to their magnetization and coercivity [48].This review presents some basic principles of X-ray optics and X-ray microscopy as well as X-ray beam dosimetry that are relevant for FXBID experiments. In accordance, limitations, challenges and opportunities of additiv...

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Overview of nanoscale NEXAFS performed with soft X-ray microscopes

Cited by 24 publications

References 67 publications

Response to referee Adam Hitchcock

Response to referee Adam Hitchcock

Development of a scanning soft X-ray spectromicroscope to investigate local electronic structures on surfaces and interfaces of advanced materials under conditions ranging from low vacuum to helium atmosphere

Additive Nano-Lithography with Focused Soft X-rays: Basics, Challenges, and Opportunities

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