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We investigate the effective oxidation state and local environment of yttrium in photochromic YHO thin film structures produced by e-beam evaporation, along with their chemical structure and optical properties. Transmission electron microscopy images reveal the oxidized yttrium hydride thin film sample exhibiting a three-layered structure. X-ray photoelectron spectroscopy (XPS) measurements manifest that the oxidation state of yttrium is modified, dependent on the film's composition/depth. Furthermore, Ion beam analysis confirms that this variability is associated with a composition gradient within the film. X-ray absorption spectroscopy at the Y K-edge reveals that the effective oxidation state of yttrium is approximately +2.5 in the transparent/bleached state of YHO. Spectroscopic ellipsometry investigations showed a complex non-linear optical depth profile of the related sample confirming the dominant phase of YHO and the presence of Y2O3 and Y towards the middle of the film. The first evidence of (n; k) dispersion curves for e-beam sputtered photochromic YHO thin films are reported for transparent and dark states. [ABSTRACT FROM AUTHOR]

The following research paper concerns the analysis and characterisation of commercially available surface-enhanced Raman scattering (SERS) substrates. SERS has long been a potentially very powerful method with a great deal of interest around it; however, there are still many obstacles which do not allow SERS to be easily applied to real-world detection and analysis problems. As such, research around the various types of substrates is ongoing, in the hope of streamlining and improving the Raman enhancement mechanism. Scanning electron microscope images were obtained for each of the three substrates, and their features and scales were described. Enhanced Raman spectra for Rhodamine B were obtained for a range of concentrations using each of the three substrates, and, in addition, surface enhancement maps are presented. Enhancement factors were calculated for the 1358 cm−1 peak of Rhodamine B. Complementing the experimental work, theoretical FEM modelling in COMSOL Multiphysics was performed, with the resulting calculations yielding an enhancement prediction adequately accurate to the real substrates. [ABSTRACT FROM AUTHOR]

We demonstrated the linear, radial, and annular ripple formation on the surface of GaAs. The formation of linear ripples was optimized by the number of shots and the fluence of 30 ps, 532 nm pulses. The radial and annular nanoripples were produced under the ablation using doughnut-like beams possessing azimuthal and radial polarizations, respectively. We compare the ripples and grooves formed by a linearly polarized Gaussian beam relative to an annular vector beam. The joint overlap of sub-wavelength grooves with ripples formed by azimuthally and radially polarized beams was reported. The conditions under which the shape of radial and ring-like nano- or micro-relief on the GaAs surface can be modified by modulating the polarization of laser pulse were determined. The resultant surface processing of GaAs using a laser beam with different polarization modes is useful for exploring valuable insights and benefits in different applications. [ABSTRACT FROM AUTHOR]

A pn‐heterojunction is fabricated by depositing an n‐type β‐Ga2O3 film by pulsed laser deposition (PLD) on c‐cut Al2O3. P‐type cuprous oxide films, Cu2O, are then deposited by PLD, as well as by radio frequency (RF) magnetron sputtering. It is concluded that hole injection is prohibited by a 3.26 eV valence band barrier, as measured by X‐ray photo‐electron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). Heterojunction diode structures are prepared on the front side and electrical measurements demonstrate a rectification ration of 8 orders of magnitude and an ideality factor close to 2, indicating interface recombination‐controlled forward current. The junction is also optically active and shows a very fast photo‐response to 275 nm UV light. [ABSTRACT FROM AUTHOR]

This study presents a thorough investigation of Na2FeP2O7 (NFP) cathode material for sodium-ion batteries and its composites with carbon and reduced graphene oxide (rGO). Our findings demonstrate that rGO sheets improve cycling performance in NFP/C/rGO composite in the absence of solid electrolyte interphase (SEI)-stabilizing additives. However, once SEI is stabilized with the help of fluoroethylene carbonate electrolyte additive, NFP with carbon additive (NFP/C) exhibits a superior electrochemical performance when compared to NFP/rGO and NFP/C/rGO composites. The decreases in capacity and rate capability are proportional to the amount of rGO added, and lead to an increase in overvoltage and internal resistance. Based on our results, we attribute this effect to worsened sodium kinetics in the bulk of the electrode—the larger ionic radius of Na+ hinders charge transfer in the presence of rGO, despite the likely improved electronic conductivity. These findings provide a compelling explanation for the observed trends in electrochemical performance and suggest that the use of rGO in Na-ion battery electrodes may present challenges associated with ionic transport along and through rGO sheets. [ABSTRACT FROM AUTHOR]