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Understanding of single-layer and bilayer thin films of WO3 and Ta2O5 for electrochromic applications remains elusive. In this study, single layers of WO3 and Ta2O5 and bilayer thin films of WO3/Ta2O5 and Ta2O5/WO3 were prepared by the sol–gel method followed by spin coating. X-ray diffraction (XRD) analysis revealed the semicrystalline nature of WO3 and the absence of significant crystalline planes in Ta2O5. Raman spectroscopy confirmed the characteristic vibrational modes of WO3 and Ta2O5 in both single-layer and bilayer thin films. Enhancement in cyclic voltammetry (CV) was observed in Ta2O5/WO3 compared to other thin films. Additionally, Ta2O5/WO3 exhibited a greater change in transmittance (ΔT) relative to other configurations. The impact of proton irradiation on the thin films was further investigated, revealing modifications in their structural and phonon vibrational properties. Notably, the CV performance of the irradiated thin films was drastically reduced. X-ray absorption spectroscopy (XAS) provided insights into the modulation of hybridization of O with W/Ta and the charge states of W and Ta in the thin films. This study provides a comprehensive understanding of single-layer and bilayer electrochromic thin films and their response to proton irradiation, paving the way for the development of space-applicable electrochromic bilayer thin films with improved performance and stability. [ABSTRACT FROM AUTHOR]

Pulsed-laser deposition was utilized to fabricate Eu-doped ZnO epitaxial films on c-plane sapphire substrates with Eu concentrations ranging from 0.5 to 4.0 at. %. The structural properties were analyzed using x-ray diffraction surface normal radial scans and azimuthal cone scans, which confirmed the epitaxy of the film samples. Reciprocal space mapping was performed on ZnO(10 1 ̄ 1) to visualize the effect of Eu incorporation. X-ray fluorescence mapping confirmed the homogeneous distribution of Zn and Eu, and x-ray absorption near-edge structure spectra directly confirmed the trivalent state of Eu ions. The optical properties were assessed using temperature-dependent photoluminescence (PL). Various defects were identified. With increasing Eu dopant concentration, PL emissions from defects and the Eu 4f-intraband transitions gradually became the predominant features in the PL spectra at low temperatures. Furthermore, PL analysis suggested that Eu ions substituted Zn, occupying sites with lower C3v symmetry due to the distortion caused by Eu incorporation. [ABSTRACT FROM AUTHOR]

Anionic redox allows the direct formation of O─O bonds from lattice oxygens and provides higher catalytic in the oxygen evolution reaction (OER) than does the conventional metal ion mechanism. While previous theories have predicted and experiments have suggested the possible O─O bond, it has not yet been directly observed in the OER process. In this study, operando soft X‐ray absorption spectroscopy (sXAS) at the O K‐edge and the operando Raman spectra is performed on layered double CoFe hydroxides (LDHs) after intercalation with [Cr(C2O4)3]3−, and revealed a three‐step oxidation process, staring from Co2+ to Co3+, further to Co4+ (3d6L), and ultimately leading to the formation of O─O bonds and O2 evolution above a threshold voltage (1.4 V). In contrast, a gradual oxidation of Fe is observed in CoFe LDHs. The OER activity exhibits a significant enhancement, with the overpotential decreasing from 300 to 248 mV at 10 mA cm−2, following the intercalation of [Cr(C2O4)3]3− into CoFe LDHs, underscoring a crucial role of anionic redox in facilitating water splitting. [ABSTRACT FROM AUTHOR]

MoSSe is a semiconducting material with a layered structure similar to MoS2 and MoSe2, which shows potential applications in optoelectronics, solar cells, sensing, and catalysis. Synthesis of this material with a controllable structure and chemical composition represents a great challenge. Herein, we report a new method for the synthesis of MoSSe by employing an [Et4N]2[Mo3S4Se3Br6] complex as the sole precursor. Thermal annealing of this complex under an Ar atmosphere at moderate temperatures ranging from 350 °C to 650 °C resulted in the formation of pure MoSSe. The morphology and structure of MoSSe were characterized using SEM, HRTEM, XRD, Raman spectroscopy, X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). The effects of annealing temperature on the structure of MoSSe were also examined. [ABSTRACT FROM AUTHOR]

This study was meticulously conducted, delving into the epitaxial growth of nanothin β-In2Se3 films on sapphire (0001) using molecular beam epitaxy. The growth temperature was carefully set at 480 °C, and the selenium to indium flux ratio (RSe/In) was systematically varied from 1 to 100. The phase transformation from γ-In2Se3 to β-In2Se3 was precisely controlled by manipulating the RSe/In and confirmed through Raman scattering measurements and synchrotron-based grazing-incidence wide-angle X-ray scattering. The surface morphology for various RSe/In of In2Se3 was analyzed by atomic force microscopy (AFM). The lowest surface roughness is around 0.58 nm, which is achieved under the RSe/In = 60 growth condition. The nanothin β-In2Se3 film with a layer-by-layer atomic arrangement was verified by high-resolution transmission electron microscopy. According to the experimental results, the growth dynamics of In2Se3 are proposed to be step-flow growth and horizontal growth under RSe/In 45 and 60 conditions, respectively. This research underscores the control of the growth mechanism by Se/In flux and its role in facilitating the In2Se3 epitaxy for integration in the development of 2D-materials-based future electronic devices. [ABSTRACT FROM AUTHOR]

Integrating two-dimensional (2D) layered materials with wide bandgap β-Ga2O3 has unveiled impressive opportunities for exploring novel physics and device concepts. This study presents the epitaxial growth of 2D β-In2Se3/3D β-Ga2O3 heterostructures on c-Sapphire substrates by plasma-assisted molecular beam epitaxy. Firstly, we employed a temperature-dependent two-step growth process to deposit Ga2O3 and obtained a phase-pure (2 ¯ 01) β-Ga2O3 film on c-Sapphire. Interestingly, the in-situ reflective high-energy electron diffraction (RHEED) patterns observed from this heterostructure revealed the in-plane 'b' lattice constant of β-Ga2O3 ~ 3.038Å. In the next stage, for the first time, 2D In2Se3 layers were epitaxially realized on 3D β-Ga2O3 under varying substrate temperatures (Tsub) and Se/In flux ratios (RVI/III). The deposited layers exhibited (00l) oriented β-In2Se3 on (2 ¯ 01) β-Ga2O3/c-Sapphire with the epitaxial relationship of [ 11 2 ¯ 0 ] β-In2Se3 || [010] β-Ga2O3 and [ 10 1 ¯ 0 ] β-In2Se3 || [102] β-Ga2O3 as observed from the RHEED patterns. Also, the in-plane 'a' lattice constant of β-In2Se3 was determined to be ~ 4.027Å. The single-phase β-In2Se3 layers with improved structural and surface quality were achieved at a Tsub ~ 280 °C and RVI/III ~ 18. The microstructural and detailed elemental analysis further confirmed the epitaxy of 2D layered β-In2Se3 on 3D β-Ga2O3, a consequence of the quasi-van der Waals epitaxy. Furthermore, the β-Ga2O3 with an optical bandgap (Eg) of ~ 5.04 eV (deep ultraviolet) when integrated with 2D β-In2Se3, Eg ~ 1.43eV (near infra-red) can reveal potential applications in the optoelectronic field. [ABSTRACT FROM AUTHOR]

Molecular beam epitaxy (MBE) is demonstrated as an excellent growth technique for growing a low-defect GaN channel layer, which is crucial for controlling vertical leakage current and improving breakdown voltage (BV) in GaN-based high-electron mobility transistors (HEMTs). The 3D islands to 2D growth mode transition approach was induced by modulating substrate growth temperature (Tsub), displaying an overall improvement in film quality. A comprehensive investigation was conducted into the effects of Tsub on surface morphologies, crystal quality, and the optical and electrical properties of GaN films. Optimal results were achieved with a strain-relaxed GaN film grown at 690 °C, exhibiting significantly improved surface characteristics (root-mean-square roughness, Rq = 0.3 nm) and impressively reduced edge dislocations. However, the film with the smoothest surface roughness, attributed to the effect of the Ga-rich condition, possessed a high surface pit density, negatively affecting optical and electrical properties. A reduction in defect-related yellow emission further confirmed the enhanced crystalline quality of MBE GaN films. The optimized GaN film demonstrated outstanding electrical properties with a BV of ~1450 V, surpassing that of MOCVD GaN (~1180 V). This research significantly contributes to the advancement of MBE GaN-based high electron mobility transistor (HEMT) applications by ensuring outstanding reliability. [ABSTRACT FROM AUTHOR]