| 1. |
- Greczynski, Grzegorz, et al.
(författare)
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X-ray photoelectron spectroscopy of thin films
- 2023
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Ingår i: NATURE REVIEWS METHODS PRIMERS. - : SPRINGERNATURE. - 2662-8449. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- X-ray photoelectron spectroscopy (XPS) is a popular analytical technique in materials science as it can assess the surface chemistry of a broad range of samples. This Primer concerns best practice in XPS analysis, aimed at both entry-level and advanced users, with a focus on thin film samples synthesized under vacuum conditions. The high surface to volume ratio of thin films means that factors such as substrate choice and air exposure time are important for the final result. Essential concepts are introduced, such as binding energy, photoelectric effect, spectral referencing and chemical shift, as well as practical aspects including surface sensitivity, probing depth, energy resolution, sample handling and sputter etching. Correct procedures for experimental planning, instrument set-up, sample preparation, data acquisition, results analysis and presentation are reviewed in connection with physical principles and common applications. Typical problems, including charging, spectral overlap, sputter damage and binding energy referencing, are discussed along with possible solutions or workarounds. Finally, a workflow is presented for arriving at high-quality results. X-ray photoelectron spectroscopy (XPS) can be used to investigate chemical bonding and elemental composition. This Primer discusses how XPS can be used to characterize thin films, including key considerations for sample preparation, experimental set-up and data analysis.
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| 2. |
- Hellgren, Niklas, et al.
(författare)
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Interpretation of X-ray photoelectron spectra of carbon-nitride thin films: New insights from in situ XPS
- 2016
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Ingår i: Carbon. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0008-6223 .- 1873-3891. ; 108, s. 242-252
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Tidskriftsartikel (refereegranskat)abstract
- We report on angular-resolved x-ray photoelectron spectroscopy (XPS) studies of magnetron sputtered CNx thin films, first in situ (without air exposure), then after air exposure (for time periods ranging from minutes to several years), and finally after Ar ion etching using ion energies ranging from 500 eV to 4 keV. The as-deposited films typically exhibit two strong N1s peaks corresponding to pyridine-like, and graphite-like, at similar to 398.2 eV and similar to 400.7 eV, respectively. Comparison between in situ and air-exposed samples suggests that the peak component at similar to 402-403 eV is due only to quaternary nitrogen and not oxidized nitrogen. Furthermore, peak components in the similar to 399-400 eV range cannot only be ascribed to nitriles or pyrrolic nitrogen as is commonly done. We propose that it can also be due to a polarization shift in pyridinic N, induced by surface water or hydroxides. Argon ion etching readily removes surface oxygen, but results also in a strong preferential sputtering of nitrogen and can cause amorphization of the film surface. The best methods for evaluating and interpreting the CNx film structure and composition with ex-situ XPS are discussed. (C) 2016 Elsevier Ltd. All rights reserved.
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| 3. |
- Mei, Antonio B., et al.
(författare)
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Adsorption-controlled growth and properties of epitaxial SnO films
- 2019
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Ingår i: Physical Review Materials. - : AMER PHYSICAL SOC. - 2475-9953. ; 3:10
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Tidskriftsartikel (refereegranskat)abstract
- When it comes to providing the unusual combination of optical transparency, p-type conductivity, and relatively high mobility, Sn2+-based oxides are promising candidates. Epitaxial films of the simplest Sn2+ oxide, SnO, are grown in an adsorption-controlled regime at 380 degrees C on Al2O3 substrates by molecular-beam epitaxy, where the excess volatile SnOx desorbs from the film surface. A commensurately strained monolayer and an accompanying van der Waals gap is observed near the substrate interface, promoting layers with high structural perfection notwithstanding a large epitaxial lattice mismatch (-12%). The unintentionally doped films exhibit p-type conductivity with carrier concentration 2.5 x 10(16) cm(-3) and mobility 2.4 cm(2) V(-1)s(-1) at room temperature. Additional physical properties are measured and linked to the Sn2+ valence state and corresponding lone-pair charge-density distribution.
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| 4. |
- Sang, Lingzi, et al.
(författare)
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Understanding the Effect of Interlayers at the Thiophosphate Solid Electrolyte/Lithium Interface for All-Solid-State Li Batteries
- 2018
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Ingår i: Chemistry of Materials. - : AMER CHEMICAL SOC. - 0897-4756 .- 1520-5002. ; 30:24, s. 8747-8756
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Tidskriftsartikel (refereegranskat)abstract
- All-solid-state Li-ion batteries afford possibilities to enhance battery safety while improving their energy and power densities. Current challenges for achieving high-performance all-solid-state batteries with long cycle life include shorting resulting predominantly from Li dendrite formation and infiltration through the solid electrolyte (SE) and increases in cell impedance induced by SE decomposition at the SE/electrode interface. In this work, we evaluate the electrochemical properties of two interlayer materials, Si and LixAl(2-x/3)O3 (LiAlO), at the Li7P3S11 (LPS)/Li interface. Compared to the Li/LPS/Li symmetric cells in absence of interlayers, the presence of Si and LiAlO both significantly enhance the cycle number and total charge passing through the interface before failures resulting from cell shorting. In both cases, the noted improvements were accompanied by cell impedances that had increased substantially. The data reveal that both interlayers prevent the direct exposure of LPS to the metallic Li and therefore eliminate the intrinsic LPS decomposition that occurs at Li surfaces before electrochemical cycling. After cycling, a reduction of LPS to Li2S occurs at the interface when a Si interlayer is present; LiAlO, which functions to drop the potential between Li and LPS, suppresses LPS decomposition processes. The relative propensities toward SE decomposition follows from the electrochemical potentials at the interface, which are dictated by the identities of the interlayer materials. This work provides new insights into the phase dynamics associated with specific choices for SE/electrode interlayer materials and the requirements they impose for realizing high efficiency, long lasting all-solid-state batteries.
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