Journal of Electron Spectroscopy and Related Phenomena最新文献

Angle-Resolved Photoemission Spectroscopy (ARPES) is a premier technique for understanding the electronic excitations in conductive, crystalline matter, in which the induced photocurrent is collected and dispersed in energy and angle of emission to reveal the energy- and momentum-dependent single particle spectral function $A(k,\omega )$. So far, ARPES in a magnetic field has been precluded due to the need to preserve the electron paths between the sample and detector. In this paper we report progress towards “magnetoARPES”, a variant of ARPES that can be conducted in a magnetic field. It is achieved by applying a microscopic probe beam ($\lesssim$10 $\mu m$) to a thinned sample mounted upon a special sample holder that generates magnetic field confined to a thin layer near the sample surface. In this geometry we could produce ARPES in magnetic fields up to around ±100 mT. The magnetic fields can be varied from purely in-plane to nearly purely out-of-plane, by scanning the probe beam across different parts of the device. We present experimental and simulated data for graphene to explore the aberrations induced by the magnetic field. These results demonstrate the viability of the magnetoARPES technique for exploring symmetry breaking effects in weak magnetic fields.

Methylammonium lead iodide CH₃NH₃PbI₃ (MAPI) is one of the hybrid organic–inorganic perovskites (HOIPs) widely considered for photovoltaic devices. Since photoemission is possibly the best technique for the experimental determination of the bands, we have calculated photoemission spectra at the main photon energies available at conventional laboratories (He I - 21.2 eV, He II - 40.8 eV) by performing fully relativistic Spin-Polarized Relativistic Korringa–Kohn–Rostoker (SPRKKR) calculations. Similarly, we have studied how s- and p-polarization affect to the calculated spectra. These studies could help to reach a better understanding of photoemission measurements on MAPI.

Scanning transmission X-ray microscopy (STXM) in the soft X-ray range is well-suited to study ultrastructural features of mammalian soft tissues. Especially at the carbon 1s edge, the imaging contrast varies drastically across the edge due to rapid changes in the X-ray absorption cross-section of functional groups present in the tissue samples enabling label-free soft X-ray spectromicroscopic studies. We present STXM spectromicroscopic imaging of mouse kidney and liver tissues. We especially concentrate on ultrastructural abnormalities in genetically modified Slc17a5 mice. STXM is a promising technique to study storage diseases without chemical alteration due to staining agents, but sample preparation poses a challenge.

The surface properties of the spray-deposited Mg-doped ZnS and ZnSe films were investigated using X-ray photoelectron spectroscopy (XPS). The energy levels of the core electrons in ZnMgS and ZnMgSe, their peak positions, area ratios, and full width at half maximum were determined. Chemical shifts in Auger peaks, which are highly sensitive to changes in the chemical environment were used in the analysis. Compositional analysis indicated selenium deficiency in the ZnMgSe films. XPS peak of magnesium 2p showed a shift from 50.46 eV for ZnMgSe film to 50.63 eV for ZnMgS film and Mg 2s peak shift from 86.56 eV for ZnMgSe to 87.64 eV for ZnMgS films. A careful justification for the formation of oxides in the ZnMgSe films is also given. Ionicity for both films is about 0.51. Peak shifts in the Auger and core-level peaks are used to analyze the material's bonding strength, oxidation states, and bonding types.

The synchrotron x-ray spectromicroscopy technique Scanning Transmission X-ray Microscopy (STXM) offers a powerful means to examine the underlying biochemistry of biological systems, owing to its combined chemical sensitivity and nanoscale spatial resolution. Here we introduce and demonstrate methodology for the use of STXM to examine the biochemistry of the human brain. We then discuss how this approach can help us better understand the biochemical changes that occur during the development of degenerative brain disorders, potentially facilitating the development of new therapies for disease diagnosis and treatment.

Soft X-ray spectro-ptychography of nickel-nitrogen-carbon electrocatalysts containing atomically dispersed Ni-based active sites were measured at the Ni L₃ edge. Samples prepared with two different loadings of Ni precursors were investigated and compared to the results of an earlier study using scanning transmission X-ray microscopy (STXM) [Zhang et al., ACS Catalysis 12 (2022) 8746]. The ptychography data sets were measured using a defocused probe (1–3 µm). The spatial resolution was improved from ∼60 nm (STXM) to ∼20 nm (ptychography). Spectro-ptychography stacks were measured at 4 component-specific energies (4-E stack) and at many energies across the full Ni L₃ edge (34-E stack). Maps of three key chemical components (Ni metal, Ni₃S_2, and atomically dispersed N-coordinated Ni catalyst sites) were derived by fits of suitable reference spectra to absorption signals derived from the amplitude images from ptychographic reconstruction. The spectro-ptychography 4-E and 34-E stacks gave chemical mapping similar to each other and to the earlier STXM results. The phase signals obtained from the same data set and reconstruction were also found to be analyzable using reference phase spectra extracted from the phase stack, which generated chemical maps similar to those based on ptychography amplitude data. By using a defocused probe, the radiation dose and acquisition times for spectro-ptychography are comparable to conventional STXM, but significantly improved spatial resolution was achieved. This study highlights the added value of spectro-ptychography relative to STXM for studies of electrocatalysts.

Calcium minerals are ubiquitous in geology and life chemistry. Understanding the phase and chemical state of calcium minerals is important for numerous processes including materials chemistry, hard tissue biogenesis and geological processes. Photoemission spectroscopies such as near edge X-ray absorption fine structure (NEXAFS) and scanning transmission X-ray microscopy have been instrumental in identifying and characterizing calcium minerals in all these areas. In this work, we have recorded reference spectra for a range of different calcium minerals including a series of calcium carbonates, calcium oxalates and calcium phosphates. While collections of reference spectra for several calcium minerals can be found in the literature, these spectra have been reported in different contexts using a variety of instruments. We, here, report a comprehensive list of references recorded in parallel in a single experiment by imaging an array of calcium minerals using a NEXAFS microscope. We present reference NEXAFS spectra at the calcium L-, carbon K- and oxygen K-edges.

The beamline, BL4U, in UVSOR-III Synchrotron is dedicated to scanning transmission X-ray microscopy (STXM) based on 2-dimensional soft X-ray absorption and has been in operation since 2013, to enable both academic and industrial users to carry out advanced chemical analysis under various sample environments. In this paper, we have summarized our major developments for the last decade; especially, expansion of the photon energy range down to the Li K-edge (55 eV), sample cryo-cooling to reduce radiation damage, 3-dimensional computer tomography, and air-free sample transfer.

In this paper, we give an overview of the nanoscale spectromicroscopy studies performed with the full-field X-ray microscope at the BESSY II electron storage ring. We do not consider spectromicroscopy studies performed with X-ray microscopes operated at other synchrotron sources. Such studies can be found in the literature. To our knowledge, the full-field X-ray microscope at the BESSY II storage ring is the first one operating with both a plane-grating-monochromator (PGM) beamline equipped with multi-layer optics for the tender X-ray range, as well as with standard optical elements for the soft X-ray range. We discuss how this instrument has been used in various published NEXAFS-TXM studies to probe low dimensional nanostructures. This research work paves the way for understanding electronic structures approaching the atomic scale, and will thereby help in the design of tailored functional systems.

Metal-halide perovskites are complex materials with outstanding optoelectronic properties. Thus it is of interest to analyze these materials by using every available research tool. Synchrotron tools have played an important role in fundamental and applied research for decades. Many synchrotron-based hard X-ray tools are already providing effective feedback to the perovskite solar cell (PSC) research community. With several fourth-generation light sources up and running or under development, this contribution will continue to impact every aspect of scientific advancement including PSC research. Arguably, the contribution of soft X-rays in PSC research is relatively limited. In view of the developments in the synchrotron world and the fact that a multimethod approach, combining laboratory-based techniques as well as synchrotron-based techniques, is necessary to provide constructive feedback to the PSC community we present here a collection of arguments and procedures with the aim of highlighting the use of soft X-ray scanning transmission X-ray microscopy (STXM). Some aspects of these arguments are elaborated with STXM investigation of perovskite material formamidinium-methylammonium lead iodide (FA_1−xMA_xPbI₃).