Journal of Electron Spectroscopy and Related Phenomena最新文献

Single crystalline LiFe_0.6Mn_0.4PO₄ (LFMP) nanowires with carbon sheath were analyzed by scanning transmission X-ray microscopy (STXM) with a spatial resolution of around 130 nm. The pinpoint Fe L-edge X-ray absorption spectroscopy (XAS) spectra in the STXM images revealed the natural oxidation of Fe²⁺ to Fe³⁺ near the tip of the nanowire by air exposure. The pinpoint O K-edge XAS spectra simultaneously changed with the Fe L-edge XAS in the STXM mapping because of the hybridization between the O 2p and Fe 3d orbitals. On the other hand, the Mn L-edge XAS spectra showed an almost uniform Mn²⁺ state all over the nanowires, suggesting that the Mn²⁺ state is stable against the natural oxidation in contrast to the Fe²⁺ state. We have thus demonstrated that STXM is a useful technique to visualize oxidized areas of materials and to reveal detailed information about their electronic structure.

In this work, the saddle-point variation combined with complex-rotation methods are used to calculate term energies, radiative transition wavelengths and Auger transition energies of the 1s2s²2p² (²S, ²P, ²D, ⁴P), 1s2s²2p3p (²S, ²P, ²D), 1s2s2p³ (^2,4S°, ^2,4P°, ^2,4D°), and 1s2p⁴ (²S, ²P, ²D, ⁴P) resonances for F⁴⁺. The present term energies, radiative rates, radiative transition wavelengths, Auger rates and corresponding transition energies agree well with the multiconfiguration Dirac-Fock calculation results listed in the literature. Other transition data in this work are expected to offer reference values for future studies.

CO₂ electrochemical reduction (CO₂ER) is a promising technology that can convert CO₂ into useful chemicals and fuels with simultaneously reducing greenhouse gas emissions. Cu nanoparticles-based catalysts are an optimal choice of CO₂ER due to its excellent conductivity and catalytic activity. In this study, we combined scanning transmission X-ray microscopy (STXM) and spectro-ptychography to investigate the chemical and electronic structural changes of the CuAg nanocatalysts before and after CO₂ER. We observed that Cu species with the same valence state self-aggregate into separated phases. For the spent CuAg nanocatalysts after CO₂ER, most Cu(I) and Cu(0) species are oxidized to Cu(II) together with CuO transforming into undetermined Cu(II) species. We believe these mechanisms are the key reason why the CuAg nanocatalysts lost catalytic activity. Such information will be highly valuable for understanding Cu nanoparticles catalyzed CO₂ER.

Plasma discharge lamps are widely utilized in the practice of angle-resolved photoemission spectroscopy (ARPES) experiments as narrow-linewidth ultraviolet photon sources. However, many emission lines such as Ar-I, Ne-I, and Ne-II have closely spaced doublet emission lines, which result in superimposed replica on the measured ARPES spectra. Here, we present a simple method for subtracting the contribution of these doublet emission lines from photoemission spectra. Benchmarking against ARPES spectra of well-characterized 2D materials, we demonstrate that this algorithm manages to subtract the doublet signal and reproduce the key features of the monochromated He-I$\alpha$ spectra in a physically sound manner that reliably reproduces quantifiable dispersion relations and quasiparticle lifetimes.

The structural and compositional properties of tin halide perovskites (CH(NH₂)₂SnI₃, FASnI₃) with and without an ionic liquid of 1-Ethyl-3-methylimidazolium bis(trifluormethylsulfonyl) imide (EMITFSI) were investigated using the scanning transmission soft X-ray microscopy (STXM) and spectro-ptychography techniques at the Sn M_5,4-edge, I M_5,4-edge, O K-edge, C K-edge, and N K-edge. The study offers a comprehensive interpretation of the spectral characteristics of main components (C, N, Sn, and I) in Sn-based perovskites through STXM-based techniques and further reveals differences between the perovskite samples with and without adding EMITFSI ionic liquid. The chemical imaging of Sn and I shows that the perovskite sample without ionic liquid has Sn-rich regions in iodine cavities, while the ionic liquid-treated sample exhibits a more homogeneous perovskite phase. Furthermore, the C and N K-edge XANES resonance features support the interaction between the non-volatile ionic liquid and FA⁺, thus playing a protective role in the formation and stabilization of perovskite phase.

The interatomic Auger effect following O 1s ionization in N${}_2$O has been experimentally investigated using multi-electron coincidence spectroscopy. The expected transition energies have been established by comparison to the measured N 1s⁻¹v⁻¹ core-valence double ionization energies. We describe a procedure to eliminate the background of two competing processes contributing spectroscopic signatures to the same energy range, namely double Auger decay of the O 1s vacancy and direct single-photon double ionization into the N 1s⁻¹v⁻¹ states. While the interatomic Auger transitions could not be successfully isolated, we provide an upper boundary of the transition probability of 0.07% with respect to the dominant single Auger decay after O 1s ionization.

The scanning photoelectron microscope (SPEM), developed more than 30 years ago, has undergone numerous technical developments, providing an incredibly vast kind of feasible sample environments, which span from the traditional high spatial resolution core level based chemical analysis to insitu and operando complex experiments, including also electrochemical setups and operational electronic devices at various temperatures. Another important step ahead is overcoming the so-called pressure gap for operando studies, recently extended to near ambient values by building special environmental cells. Using recent results of conventional and unconventional experiments, obtained with SPEM at the ESCA Microscopy beamline at Elettra Sincrotrone Trieste the present review demonstrates the current potential of this type of photoelectron spectromicroscopy to explore the interfacial properties of functional materials with high spatial resolution.

Cobalt is one of the promising metal catalysts for hydrogen evolution reaction, and its catalytic performance can be further improved by supporting on graphene oxide and reduced graphene oxide as an active interface to the substrate. Scanning transmission X-ray microscopy (STXM) identifies the position-dependent functional groups on the membranes and chemical structure evolution of the Co_xO_y. The in-situ mass spectrometer analysis shows the reduction current and H₂ generation of the electrocatalyst enhanced by the addition of graphene oxide and reduced graphene oxide to Co_xO_y, as compared to the Co_xO_y on the bare substrate. The best hydrogen evolution reaction performance of Co_xO_y at − 2.5 V is correlated with the high Co³⁺ concentration existed on the reduced graphene oxide, as evidenced by the nano- and element-resolved capability of STXM. With the economical electro-reduction synthesis, this study provides brand-new insights into the critical role of substrate rGO and electrocatalyst Co_xO_y toward the design of high efficiency electrocatalyst.