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Garnet-type oxide solid electrolytes are the critical materials for all-solid-state lithium ion batteries. Nanoscale spectroscopic analysis on solid electrolytes plays a key role in bridging the gap between microstructure and properties. In this work, Auger electron spectroscopy (AES), which can directly detect lithium element and distinguish its valence state, was applied to characterize the garnet-type Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 (LLZTO). Different spectroscopy parameters were evaluated and optimal acquisition conditions were provided. Electron induced precipitation of lithium metal from LLZTO was observed. By exploring the influence factors of precipitation and combining transmission electron microscopy (TEM) and focused ion beam (FIB) experiments, the underlying mechanism of the phenomenon was revealed and previous controversy was resolved. The analysis method was also extended to other types of solid electrolytes, and this work provides a reference for future in-depth research on the structure–property relationship of solid electrolytes using AES.

This review summarizes the use of Auger Electron Spectroscopy (AES) for microchemical analysis of two different types of dielectric/(Al,Ga)N-based systems: (i) extrinsic dielectric PECVD SiO2, ALD Al2O3, and ECR-CVD SiNx films on AlxGa1−xN/GaN structures in the context of their application in microelectronic power devices and (ii) intrinsic Al2O3 films on AlN epitaxial layers grown by high-temperature oxidation for nanostructured technology of various gas/ion sensors. Particular attention is given to AES depth profiling across complete multilayer cross-sections, combining qualitative analysis of spectral line shape and intensity evolution as well as kinetic energy shifts with quantitative elemental depth distributions. This approach enables identification of chemical states and oxidation-related transformations at dielectric/semiconductor interfaces. Reported results demonstrate that AES provides micro- to nanometer-scale chemical information essential for distinguishing interfacial from the bulk properties. The capabilities and inherent limitations of AES depth profiling, including sputter-induced artifacts are also addressed, highlighting the role of optimized experimental conditions in reliable interface analysis.

— An overview of the use of electron spectroscopy for the study of the physicochemical properties of solids is carried out. It is noted that the main source of information about the electronic states of atoms is the energy distribution of electrons excited by ions, X-ray quanta, and laser beams. The paper briefly discusses the problems that exist in registering the spectra of secondary electrons obtained by exciting the surface of samples with electrons of medium (1–20 keV) energies and ways to solve these problems in order to increase the information content and accuracy of research results. A method for recording secondary electron spectra in an integral form using an Auger spectrometer is proposed, which allows one to increase the energy resolution of the method. The possibilities of the method are demonstrated by the example of experimental studies of zirconium carbide and steel X17AG18.

We describe a new instrument, the Argonne Auger Radioisotope Microscope (ARM), capable of characterizing the Auger electron (AE) emission of radionuclides, including candidates relevant in nuclear medicine. Our approach relies on event-by-event ion–electron coincidence, time-of-flight, and spatial readout measurement to determine correlated electron multiplicity and energy distributions of Auger decays. We present a proof-of-principle measurement with the ARM using x-ray photoionization of stable krypton beyond the K-edge and identify a bifurcation in the electron multiplicity distribution depending on the emission of K-LX electrons. Extension of the ARM to the characterization of radioactive sources of AE emissions is enabled by the combination of two recent developments: (1) cryogenic buffer gas beam technology to introduce Auger emitters into the detection region with well-defined initial conditions, and (2) large-area micro-channel plate detectors with multi-hit detection capabilities to simultaneously detect multiple electrons emitted in a single decay.

In this study X-ray Photoelectron Spectroscopy and Ultraviolet Photoelectron Spectroscopy were combined to investigate the effect of oxygen incorporation on the valence band behaviour of ZrO x . The Auger transitions involving valence bands are found to mimic the self-folded density of state measured using Ultraviolet Photoelectron Spectroscopy. The valence band once constructed in a sub-oxide form, stays at a fixed energy position despite the change in the stoichiometry. This behaviour is found to be useful in setting a reference for X-ray Photoelectron Spectroscopy charge correction. The results of the charged corrected spectra were compared to other methods and found to be in great agreement. Finally, a correlation between the core-level binding energy and the structural property of ZrO x is given.

Surface-sensitive information on a bulk sample can be obtained by using a low incident electron energy (low accelerating voltage/landing voltage) in a scanning electron microscope (SEM). However, topography and composition contrast obtained at low incident electron energies may not be intuitive and should be analyzed carefully. By combining an Auger electron spectrometer (AES) with a low incident electron energy SEM (LE-SEM), we investigated the SEM contrast carefully by separating the secondary electron (SE) and back-scattered electron (BSE) components with high accuracy. For this, we modified an AES to measure the electron energy in the range of 0–0.6 keV with a sample bias voltage of 0 to −0.3 keV. We could clearly observe reversed brightness of gold and carbon (graphite) in BSE images when the energy of the incident electrons was reduced to 0.2–0.3 keV. In addition, reflected electron energy spectroscopy (REELS) is known to be a tool for chemical state analysis of the sample. We demonstrated that it is possible to study the electron states of graphite, diamond, and graphene by acquiring low incident energy REELS spectra from their surfaces with the newly modified AES. This will be a new method for analyzing the electron states of local areas of a surface.

Molecules often fragment after photoionization in the gas phase. Usually, this process can only be investigated spectroscopically as long as there exists electron correlation between the photofragments. Important parameters, like their kinetic energy after separation, cannot be investigated. We are reporting on a femtosecond time-resolved Auger electron spectroscopy study concerning the photofragmentation dynamics of thymine. We observe the appearance of clearly distinguishable signatures from thymine′s neutral photofragment isocyanic acid. Furthermore, we observe a time-dependent shift of its spectrum, which we can attribute to the influence of the charged fragment on the Auger electron. This allows us to map our time-dependent dataset onto the fragmentation coordinate. The time dependence of the shift supports efficient transformation of the excess energy gained from photoionization into kinetic energy of the fragments. Our method is broadly applicable to the investigation of photofragmentation processes.

Garnet-type Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 (LLZO) is considered a promising solid electrolyte, but the surface degradation in air hinders its application for all-solid-state battery. Recent studies have mainly focused on the final products of the LLZO surface reactions due to lacking of powerful in situ characterization methods. Here, we use ambient pressure X-ray spectroscopies to in situ investigate the dynamical evolution of LLZO surface in different gas environments. The newly developed ambient pressure mapping of resonant Auger spectroscopy clearly distinguishes the lithium containing species, including LiOH, Li 2 O, Li 2 CO 3 and lattice oxygen. The reaction of CO 2 with LLZO to form Li 2 CO 3 is found to be a thermodynamically favored self-limiting reaction. On the contrary, the reaction of H 2 O with LLZO lags behind that of CO 2 , but intensifies at high pressure. More interestingly, the results provide direct spectroscopic evidence for the existence of Li + /H + exchange and reveal the importance of the initial layer formed on clean electrolyte surface in determining their air stability. This work demonstrates that the newly developed in situ technologies pave a new way to investigate the oxygen evolution and surface degradation mechanism in energy materials. Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 (LLZO) is a promising solid electrolyte but suffers from severe surface degradation in air. Here, authors use mapping of resonant Auger spectroscopy and various ambient pressure X-ray spectroscopies to elucidate the dynamical evolution of CO 2 and H 2 O on clean LLZO surfaces.

Specifically adsorbed alkali metal cations on metal electrodes have been hypothesized to influence the reduction of CO 2 . However, experimental detection of these cations during CO 2 reduction remains elusive. Herein, employing the asymmetric CH 3 deformation band of tetramethylammonium as a vibrational probe of the aqueous electrolyte–polycrystalline Au interface, we monitored the displacement of specifically adsorbed tetramethylammonium by alkali metal cations. We found that the coverage of specifically adsorbed alkali metal cations during CO 2 -to-CO reduction follows the order Li +  < Na +  < K +  < Cs + for the same bulk concentration. The alkali metal cations’ experimentally observed surface coverages correlate with their free energies of hydration. Furthermore, the rate of CO 2 -to-CO conversion increases with the coverage of specifically adsorbed alkali metal cations. Our observations suggest that the degree to which alkali metal cations undergo partial dehydration at the electrode–electrolyte interface plays a key role in their ability to promote CO 2 -to-CO reduction. Alkali metal cations influence electrocatalytic reactions, but their specific role remains elusive. Now, methyl 4 N + is established as a vibrational probe for surface-enhanced infrared absorption spectroscopy, revealing that alkali metal cations specifically adsorb on Au during CO 2 electroreduction and that their surface coverage depends on their free energy of hydration.

Electrochemical CO2 reduction reaction can be used to produce value‐added hydrocarbon fuels and chemicals by coupling with clean electrical energy. However, highly active, selective, and energy‐efficient CO2 conversion to multicarbon hydrocarbons, such as C2H4, remains challenging because of the lack of efficient catalysts. Herein, an ultrasonication‐assisted electrodeposition strategy to synthesize CuO nanosheets for low‐overpotential CO2 electroreduction to C2H4 is reported. A high C2H4 Faradaic efficiency of 62.5% is achieved over the CuO nanosheets at a small potential of −0.52 V versus a reversible hydrogen electrode, corresponding to a record high half‐cell cathodic energy efficiency of 41%. The selectivity toward C2H4 is maintained for over 60 h of continuous operation. The CuO nanosheets are prone to in situ restructuring during CO2 reduction, forming abundant grain boundaries (GBs). Stable Cu+/Cu0 interfaces are derived from the low‐coordinated Cu atoms in the reconstructed GB regions and act as highly active sites for CO2 reduction at low overpotentials. In situ Raman spectroscopic analysis and density functional theory computation reveal that the Cu+/Cu0 interfaces offer high *CO surface coverage and lower the activation energy barrier for *CO dimerization, which, in synergy, facilitates CO2 reduction to C2H4 at low overpotentials. Abundant grain boundaries involving stable Cu+/Cu0 interfaces are in situ reconstructed in the CuO nanosheets during CO2 electroreduction. The reconstructed grain boundaries with Cu+/Cu0 interfaces increase the *CO surface coverage and lower the energy barrier for *CO dimerization, leading to a record maximal half‐cell cathodic energy efficiency of 41% for C2H4 formation.