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Bulk and surface characterisation of micrometer-thick cobalt ferrite films grown by IR PLD
摘要： We have studied micrometer-thick cobalt ferrite films deposited on Si (100) single crystal substrates by nanosecond pulsed laser deposition at 1064 nm.The thickness of the deposited films (1.3 μm) was monitored by AFM. The chemical and structural characterisation of the films was carried out by Raman spectroscopy and transmission M?ssbauer spectroscopy at 300 and 26 K. For comparison purposes, transmission M?ssbauer data at these two temperatures were also recorded from a commercial cobalt ferrite powder and the home-made target used to grow the films. The surface characterisation was performed by X-Ray Photoelectron Spectroscopy (XPS) and Integral Low Energy Electron Spectroscopy (ILEEMS). XPS showed Co and Fe to be present as Co2+ and Fe3+, as expected for cobalt ferrite. The Raman spectra showed the lines characteristic of cobalt ferrite. The M?ssbauer spectra, both in the transmission and backscattering modes, were fitted to two sextets whose hyperfine parameters are in good agreement with those expected from Fe3+ cations occupying the tetrahedral and octahedral sites in the spinel-related structure. No significant differences were observed in the relative areas of the two sextets in the transmission and ILEEMS spectra, suggesting that the cation distribution at the surface and the bulk are not too different. However, the relative areas of the two components changed drastically with temperature both in the spectra of the films as in those recorded from the cobalt ferrite standards. We discuss the possible origin of the evolution with temperature of those relative areas.
关键词： X-ray photoelectron spectroscopy,Raman spectroscopy,Cobalt ferrite,M?ssbauer spectroscopy,Pulsed laser deposition
更新于2025-09-10 09:29:36
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Cross-Section Analysis of the Composition of Sprayed Cu <sub/>2</sub> ZnSnS <sub/>4</sub> Thin Films by XPS, EDS, and Multi-Wavelength Raman Spectroscopy
摘要： A detailed cross-section analysis of the chemical composition of sprayed Cu2ZnSnS4 thin films is presented. X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy (with near-IR, visible, and UV-lasers) are used to demonstrate that while CZTS effectively forms within the bulk of the film, there is some degree of element segregation, formation of undesirable secondary phases, and the presence of a disordered kesterite structure across the film. Different penetration depths of the excitation signals correspond to the many different surface sensitive techniques employed in this work. XPS results reveal that the surface of Cu4ZnSnS4 (CZTS) films presents a high concentration of tin and zinc and a low sulfur concentration, while being highly depleted in copper. EDS, XRD, and infrared Raman spectroscopy confirm that the composition of as-sprayed and sulfurized films is close to stoichiometric Cu2ZnSnS4. Resonant UV-Raman spectroscopy helps to identify secondary phases located at the external surface of sprayed and sulfurized CZTS films (mainly ZnS, ZnO), while VIS-Raman spectroscopy helps to identify a disordered kesterite structure close to the surface. Secondary phases need to be chemically etched when aiming at incorporating kesterite films obtained by spray pyrolysis into photovoltaic devices.
关键词： multi-wavelength Raman spectroscopy,X-ray photoelectron spectroscopy,spray pyrolysis,thin films,kesterite
更新于2025-09-10 09:29:36
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Silicon Oxide-Rich Diamond-Like Carbon: A Conformal, Ultrasmooth Thin Film Material with High Thermo-Oxidative Stability
摘要： Silicon oxide-containing diamond-like carbon (a-C:H:Si:O) films are a promising class of protective coatings for environmentally-demanding applications owing to their lower residual stresses and superior thermal stability and oxidation resistance relative to undoped diamond-like carbon. However, existing versions of a-C:H:Si:O deposited by traditional methods such as plasma-enhanced chemical vapor deposition (PECVD) undergo substantial degradation and oxidation at temperatures above 250 °C. This, together with the difficulty of PECVD in depositing conformal coatings on complex geometries such as high-aspect-ratio features, has limited the applicability of a-C:H:Si:O. Here, the unique capabilities of plasma immersion ion implantation and deposition (PIIID) to grow silicon oxide-rich diamond-like carbon materials that are ultrasmooth, continuous, and conformal on high-aspect-ratio topographies are explored. The high concentration of silicon and oxygen in PIIID-grown films (23 ± 5 at.% and 11 ± 4 at.%, respectively) is unrivalled for this class of materials, and drastically increases the resistance to oxidation at high temperatures, compared with PECVD-grown films. The results open the path for using a-C:H:Si:O in applications involving exposure of materials to extreme environments.
关键词： ultrasmooth films,X-ray photoelectron spectroscopy (XPS),diamond-like carbon,NEXAFS,thermal stability
更新于2025-09-10 09:29:36
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Water Dissociation and Hydroxyl Ordering on Anatase
摘要： We studied the interaction of water with the anatase TiO2e001T surface by means of scanning tunneling microscopy, x-ray photoelectron spectroscopy, and density functional theory calculations. Water adsorbs dissociatively on the ridges of a (1 × 4) reconstructed surface, resulting in a (3 × 4) periodic structure of hydroxyl pairs. We observed this process at 120 K, and the created hydroxyls desorb from the surface by recombination to water, which occurs below 300 K. Our calculations reveal the water dissociation mechanism and uncover a very pronounced dependence on the coverage. This strong coverage dependence is explained through water-induced reconstruction on anatase TiO2e001T-e1 × 4T. The high intrinsic reactivity of the anatase TiO2e001T surface towards water observed here is fundamentally different from that seen on other surfaces of titania and may explain its high catalytic activity in heterogeneous catalysis and photocatalysis.
关键词： x-ray photoelectron spectroscopy,scanning tunneling microscopy,anatase TiO2,hydroxyl ordering,density functional theory,water dissociation
更新于2025-09-10 09:29:36
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Zirconium distribution in solution-derived BaZrO3 - YBa2Cu3O7-δ epitaxial thin films studied by X-ray photoelectron spectroscopy
摘要： Superconducting YBa2Cu3O7-δ films with different amounts of BaZrO3 nanoinclusions were deposited on SrTiO3(001) by low-fluorine chemical solution deposition with the aim of introducing artificial vortex pinning centres. The Zr concentration over the film thickness could be determined by X-ray photoelectron spectroscopy combined with Ar+ ion etching. The Zr/Y ratio has a constant behaviour in the film's bulk. Zr segregation occurs near the surface and Zr diffusion into the substrate is observed near the interface. Conversely, Sr and Ti from the substrate diffuse into the films. Y3d lineshape analysis and X-Ray Diffraction data pointed out that Ti diffusion causes the formation of Y-Ti-O based spurious phases.
关键词： Chemical solution deposition,X-ray photoelectron spectroscopy,Vortex pinning,Yttrium barium copper oxide,Barium zirconate
更新于2025-09-10 09:29:36
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Band alignment of atomic layer deposited SiO <sub/>2</sub> on (010) (Al <sub/>0.14</sub> Ga <sub/>0.86</sub> ) <sub/>2</sub> O <sub/>3</sub>
摘要： The (AlxGa1?x)2O3/Ga2O3 system is attracting attention for heterostructure ?eld effect transistors. An important device design parameter is the choice of gate dielectric on the (AlxGa1?x)2O3 and its band alignment at the heterointerface. The valence band offset at the SiO2/(Al0.14Ga0.86)2O3 heterointerface was measured using x-ray photoelectron spectroscopy. The SiO2 was deposited by atomic layer deposition (ALD) onto single-crystal β-(Al0.14Ga0.86)2O3 grown by molecular beam epitaxy. The bandgap of the SiO2 was determined by re?ection electron energy loss spectroscopy as 8.7 eV, while high resolution XPS data of the O 1s peak and onset of elastic losses were used to establish the (Al0.14Ga0.86)2O3 bandgap as 5.0 eV. The valence band offset was determined to be 1.60 ± 0.40 eV (straddling gap, type I alignment) for ALD SiO2 on β-(Al0.14Ga0.86)2O3. The conduction band offset was 2.1 ± 0.08 eV, providing for a strong electron transport restriction.
关键词： x-ray photoelectron spectroscopy,(Al0.14Ga0.86)2O3,SiO2,atomic layer deposition,conduction band offset,band alignment,valence band offset
更新于2025-09-10 09:29:36
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Reference Module in Chemistry, Molecular Sciences and Chemical Engineering || In Situ Photoelectron Spectroscopy
摘要： X-ray photoelectron spectroscopy (XPS) is based on the photoelectric effect, which is the emission of electrons from a solid, liquid, or gas once excited with photons (ultraviolet radiation or X-rays or even g-rays) of sufficient energy. XPS measured thus the occupied states. It is not the intensity of the radiation, which causes the emission, but the wavelength l, which is related with their frequency n and energy Ephoton via the relations Ephoton = hn = hc/l of the photons. The kinetic energy Ekin of such photoelectrons yields a spectrum which allows for the determination of the binding energy EB of electrons expelled from the core levels, and the binding energy of hybridized states is Ekin = Ephoton - EB - 4spectrometer; 4 is the work function of the spectrometer. relationship between measured variables in the valence band. The quantitative
关键词： X-ray photoelectron spectroscopy,photoelectric effect,binding energy,work function,valence band
更新于2025-09-10 09:29:36
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(TiO <sub/>2</sub> ) <sub/>1?x</sub> (TaON) <sub/>x</sub> Solid Solution for Band Engineering of Anatase TiO <sub/>2</sub>
摘要： Band engineering of anatase TiO2 was achieved by means of an anatase (TiO2)1?x(TaON)x (TTON) solid solution. Epitaxial thin films of TTON (0.1 ≤ x ≤ 0.9) were synthesized by nitrogen plasma-assisted pulsed laser deposition on (LaAlO3)0.3(SrAl0.5Ta0.5O3)0.7 substrates. Epitaxial growth of anatase TTON was confirmed by X-ray diffraction. The lattice constants of the TTON thin films increased with TaON content in accordance with Vegard’s law, indicating formation of a complete solid solution. The bandgaps, band alignment, and refractive indices of the TTON thin films were investigated by combination of spectroscopic ellipsometry and X-ray photoelectron spectroscopy. The bandgap of the anatase TTON systematically decreased with increasing x, mainly because of an upward shift in the valence band maximum caused by broadening of the valence band as a result of hybridization of the shallow N 2p orbital. The position of the conduction band minimum was rather insensitive to chemical composition, which makes the band alignment of anatase TTON suitable for photocatalytic water splitting with visible light. The refractive index of anatase TTON monotonically increased with an increase in x.
关键词： Epitaxial thin films,Vegard’s law,X-ray photoelectron spectroscopy,TTON solid solution,Band engineering,Photocatalytic water splitting,Spectroscopic ellipsometry,Nitrogen plasma-assisted pulsed laser deposition,Anatase TiO2
更新于2025-09-10 09:29:36
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A challenge for x-ray photoelectron spectroscopy characterization of Cu(In,Ga)Se2 absorbers: The accurate quantification of Ga/(Ga?+?In) ratio
摘要： CIGS (Cu(In,Ga)Se2) layers are among the more efficient photovoltaic absorbers for thin film solar cells and remain competitive in the worldwide landscape of solar cells devices and modules with also new emerging markets (flexible or metallic substrates, tandem, low or high band gap CIGS…). Their properties are governed by different key composition parameters, and among them the GGI ratio ([Ga]/[Ga]+[In])) which controls the gap value. Indeed, the GGI determination is an important metrological challenge at the surface of the CIGS layer, particularly before the buffer deposition. Using X-Ray Photoelectron Spectroscopy (XPS), we propose here a specific methodology to determine this ratio at the surface. In order to, a surface preparation of the CIGS by chemical treatments, combining an initial flattening by HBr:Br2:H2O etching with a finishing step performed in KCN:H2O, is implemented. This chemical engineering leads to a quasi “perfect” surface, flattened and cleared from surface oxide and selenide phase on which our XPS methodology for GGI determination is tested. The photopeaks choice to obtain the most coherent GGI ratio quantification is discussed. In particular we focus on the Ga3d-In4d region, situated in narrow binding energy domain, and discuss why this photopeak combination can be considered as the most adapted for a representative GGI determination. Quantitative fitting procedure of the Ga3d-In4d region is qualified on a reference epitaxial InxGa1-xAs layer and its implementation in the CIGS case is shown.
关键词： X-ray photoelectron spectroscopy,Surface chemical engineering,Gallium,Indium,copper indium gallium selenide,Surface composition
更新于2025-09-10 09:29:36
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Study of the oxidation at the Al <sub/>2</sub> O <sub/>3</sub> /GaSb interface after NH <sub/>4</sub> OH and HCl/(NH <sub/>4</sub> ) <sub/>2</sub> S passivations and O <sub/>2</sub> plasma post atomic layer deposition process
摘要： In this work, the Al2O3/GaSb interface has been studied by x-ray photoelectron spectroscopy in order to improve interfacial and electrical properties of metal–oxide–semiconductor structures based on GaSb. First, different passivations using NH4OH or (NH4)2S were studied with a dilution of 4% and 5%, respectively, in order to reduce native oxides on the GaSb surface. Then, we considered the oxidation of the Al2O3 and GaSb surface after treatments with an oxygen (O2) plasma post atomic layer deposition (ALD) process and with post deposition annealing at different temperatures. We found that (NH4)2S passivation leads to a lower quantity of native oxides on the GaSb surface and that the O2 plasma post ALD process enables the formation of an oxygen-rich layer within the Al2O3 at the interface reducing the GaSb surface oxidation after post deposition annealing of the oxide.
关键词： x-ray photoelectron spectroscopy,(NH4)2S,post deposition annealing,Al2O3/GaSb interface,NH4OH,atomic layer deposition,O2 plasma
更新于2025-09-10 09:29:36