Journal of Electron Spectroscopy and Related Phenomena最新文献

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.

In this research, electronic and optical properties of armchair (7,7), zigzag (7,0), and chiral (4,2) configurations of Single-Walled Carbon Nanotubes (SWCNT) and the effect of spin-orbit coupling (SOC) on their electronic structures were studied with density functional theory (DFT) computing. The armchair, zigzag, and chiral SWCNT structures were built using the CASTEP software. Then, this code was used to calculate the band structures, density of states and optical properties of these systems. Electronic and optical properties of SWCNT material could be influenced by its configuration, such as the bandgap energy, total density of states (TDOS) and partial density of states (PDOS), absorption coefficient, dielectric function, optical conductivity, complex refractive index, and the loss function. In the absence or presence of SOC effect, armchair, zigzag and chiral nanotubes are semiconductors. SOC causes the bandgap energy to increase and the TDOS of "armchair, zigzag, and chiral SWCNTs" to alter. These results provide crucial physical information regarding the control of the electronic properties of SWCNTs using SOC.

We report a scanning transmission X-ray microscopy (STXM) study of hematite nanorods, prototypical photoanode used in solar water splitting. Hematite nanorods were obtained by hydrothermal growth from aqueous solutions using FeCl₃ as precursor. Potentials for onset of water splitting are smaller using this synthesis method, compared to values reported for hematite photoanodes obtained by epitaxial growth. STXM revealed the presence of a hexahydrate iron chloride phase at the surface of the nanorods, which is linked to the low onset potential values. We detail the quantification approach that revealed the specific microstructure of individual hematite nanorods.

We develop a software package SPADExp (simulator of photoemission angular distribution for experiments) to calculate the photoemission angular distribution (PAD), which is the momentum dependence of spectrum intensity in angle-resolved photoemission spectroscopy (ARPES). The software can directly load the output of the first-principles software package OpenMX, so users do not need to construct tight-binding models as previous studies did for PAD calculations. As a result, we can calculate the PADs of large systems such as quasicrystals and slab systems. We calculate the PADs of sublattice systems (graphene and graphite) to reproduce characteristic intensity distributions, which ARPES has experimentally observed. After that, we investigate twisted bilayer graphene, a quasicrystal showing 12-fold rotational symmetric spectra in ARPES, and the surface states of the topological insulator ${\mathrm{Bi}}_2{\mathrm{Se}}_3$. Our calculations show good agreement with previous ARPES measurements, showing the correctness of our calculation software and further potential to investigate the photoemission spectra of novel quantum materials.

This article reviews the application of near-edge X-ray absorption fine structure (NEXAFS) spectroscopy to characterization of self-assembled monolayers (SAMs) which are an important part of modern nanotechnology, being particular useful in context of surface and interface engineering. NEXAFS spectroscopy provides information about the electronic structure of the SAMs, which allows to recognize specific functional groups and building blocks of the SAM-forming molecules. Due to the linear dichroism effects in X-ray absorption, this technique is also capable to give insight into orientational order and molecular orientation in the SAMs, both overall and building-block-specific. To illustrate the above points, a variety of representative examples for different classes of SAMs is provided, accompanied by the information about the general aspects of the technique and the description of suitable data evaluation procedures. Finally, it is shown that the application of NEXAFS spectroscopy to SAMs is not only limited by their characterization but is also useful to monitor chemical and physical processes involving these systems.

With the advent of ambient pressure X-ray excited electron spectroscopy, near-edge X-ray absorption fine structure spectroscopy is widely used to investigate the hydrogen-bonding environment in aqueous solutions, ice, and adsorbed water. When Auger-Meitner electrons are detected, the method becomes inherently surface-sensitive because of the limited escape depth of electrons. In such X-ray absorption experiments with aqueous samples, gas-phase water is inevitably present. It impacts the acquired spectra in two ways: (1) Absorption along the X-ray path upstream of the sample reduces the photon flux reaching the condensed phase. (2) Spectra originating from gas-phase water in front of the analyzer contribute to the recorded spectra. Here, we develop and discuss a procedure to disentangle the gas-phase and condensed-phase contribution in the acquired spectra. A novel approach to quantify and remove the gas-phase contribution allows receiving condensed-phase near-edge X-ray absorption fine structure spectra at high water vapor pressure free of gas-phase artifacts.