2014, Huang, Y., Fang, Y., Zhang, Z., Zhu, L., Sun, M.

Due to its amazing ability to manipulate light at the nanoscale, plasmonics has become one of the most interesting topics in the field of light-matter interaction. As a promising application of plasmonics, surface-enhanced Raman scattering (SERS) has been widely used in scientific investigations and material analysis. The large enhanced Raman signals are mainly caused by the extremely enhanced electromagnetic field that results from localized surface plasmon polaritons. Recently, a novel SERS technology called remote SERS has been reported, combining both localized surface plasmon polaritons and propagating surface plasmon polaritons (PSPPs, or called plasmonic waveguide), which may be found in prominent applications in special circumstances compared to traditional local SERS. In this article, we review the mechanism of remote SERS and its development since it was first reported in 2009. Various remote metal systems based on plasmonic waveguides, such as nanoparticle-nanowire systems, single nanowire systems, crossed nanowire systems and nanowire dimer systems, are introduced, and recent novel applications, such as sensors, plasmon-driven surface-catalyzed reactions and Raman optical activity, are also presented. Furthermore, studies of remote SERS in dielectric and organic systems based on dielectric waveguides remind us that this useful technology has additional, tremendous application prospects that have not been realized in metal systems.

2010, Rivera, C., Pereiro, J., Navarro, A., Muñoz, E., Brandt, O., Grahn, H.T.

Group-III nitrides are considered to be a strategic technology for the development of ultraviolet photodetectors due to their remarkable properties in terms of spectral selectivity, radiation hardness, and noise. The potential advantages of these materials were initially obscured by their large density of intrinsic defects. The advances were thus associated in general with improvements in material quality. Although technology still also needs improvement, efforts are being intensified in the fabrication of advanced structures for photodetector applications. In particular, this review discusses the recent progress in group-III-nitride photodetectors, emphasizing the work reported on quantum-well-based photodetectors, the use of novel structures exploiting the effect of piezoelectric polarization-induced fields, and polarization-sensitive photodetectors. Furthermore, some ideas can be generalized to other material systems such as ZnO and their related compounds, which exhibit the same crystal structure as group-III nitrides. © Rivera et al.; Licensee Bentham Open.

2021, Ozga, C., Honisch, C., Schmidt, P., Holzapfel, X., Zindel, C., Küstner-Wetekam, C., Richter, C., Hergenhahn, U., Ehresmann, A., Knie, A., Hans, A.

We report the adaptation of an electron–photon coincidence detection scheme to the multibunch hybrid mode of the synchrotron radiation source BESSY II (Helmholtz-Zentrum Berlin). Single-event-based data acquisition and evaluation, combined with the use of relative detection times between the coincident particles, enable the acquisition of proper coincidence signals from a quasi-continuous excitation pattern. The background signal produced by accidental coincidences in the time difference representation is modeled using the non-coincident electron and photon spectra. We validate the method by reproducing previously published results, which were obtained in the single bunch mode, and illustrate its usability for the multibunch hybrid mode by investigating the photoionization of CO2 into CO+2 B satellite states, followed by subsequent photon emission. The radiative lifetime obtained and the electron binding energy are in good agreement with earlier publications. We expect this method to be a useful tool to extend the versatility of coincident particle detection to arbitrary operation modes of synchrotron radiation facilities and other excitation sources without the need for additional experimental adjustments.

2014, Treske, Uwe, Heming, Nadine, Knupfer, Martin, Büchner, Bernd, Koitzsch, Andreas, Di Gennaro, Emiliano, Scotti di Uccio, Umberto, Miletto Granozio, Fabio, Krause, Stefan

LaAlO3 and NdGaO3 thin films of different thicknesses have been grown by pulsed laser deposition on TiO2-terminated SrTiO3 single crystals and investigated by soft X-ray photoemission spectroscopy. The surface sensitivity of the measurements has been tuned by varying photon energy hν and emission angle Θ. In contrast to the core levels of the other elements, the Sr 3d line shows an unexpected splitting for higher surface sensitivity, signaling the presence of a second strontium component. From our quantitative analysis we conclude that during the growth process Sr atoms diffuse away from the substrate and segregate at the surface of the heterostructure, possibly forming strontium oxide

2022, Kretschmar, M., Hadjipittas, A., Major, B., Tümmler, J., Will, I., Nagy, T., Vrakking, M. J. J., Emmanouilidou, A., Schütte, B.

Multi-electron dynamics in atoms and molecules very often occur on sub- to few-femtosecond time scales. The available intensities of extreme-ultraviolet (XUV) attosecond pulses have previously allowed the time-resolved investigation of two-photon, two-electron interactions. Here we study double and triple ionization of argon atoms involving the absorption of up to five XUV photons using a pair of intense attosecond pulse trains (APTs). By varying the time delay between the two APTs with attosecond precision and the spatial overlap with nanometer precision, we obtain information on complex nonlinear multi-photon ionization pathways. Our experimental and numerical results show that Ar2+ is predominantly formed by a sequential two-photon process, whereas the delay dependence of the Ar3+ ion yield exhibits clear signatures of the involvement of a simultaneous two-photon absorption process. Our experiment suggests that it is possible to investigate multi-electron dynamics using attosecond pulses for both pumping and probing the dynamics.

2020, Hermans Y., Klein A., Sarker H.P., Huda M.N., Junge H., Toupance T., Jaegermann W.

CuFeO2 is recognized as a potential photocathode for photo(electro)chemical water splitting. However, photocurrents with CuFeO2-based systems are rather low so far. In order to optimize charge carrier separation and water reduction kinetics, defined CuFeO2/Pt, CuFeO2/Ag, and CuFeO2/NiOx(OH)y heterostructures are made in this work through a photodeposition procedure based on a 2H CuFeO2 hexagonal nanoplatelet shaped powder. However, water splitting performance tests in a closed batch photoreactor show that these heterostructured powders exhibit limited water reduction efficiencies. To test whether Fermi level pinning intrinsically limits the water reduction capacity of CuFeO2, the Fermi level tunability in CuFeO2 is evaluated by creating CuFeO2/ITO and CuFeO2/H2O interfaces and analyzing the electronic and chemical properties of the interfaces through photoelectron spectroscopy. The results indicate that Fermi level pinning at the Fe3+/Fe2+ electron polaron formation level may intrinsically prohibit CuFeO2 from acquiring enough photovoltage to reach the water reduction potential. This result is complemented with density functional theory calculations as well. © 2020 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

2013, Roth, S., Sheppard, C.J.R., Wicker, K., Heintzmann, R.

To enhance the resolution of a confocal laser scanning microscope the additional information of a pinhole plane image taken at every excitation scan position can be used (Sheppard 1988). This photon reassignment principle is based on the fact that the most probable position of an emitter is at half way between the nominal focus of the excitation laser and the position corresponding to the (off centre) detection position. Therefore, by reassigning the detected photons to this place, an image with enhanced detection efficiency and resolution is obtained. Here we present optical photon reassignment microscopy (OPRA) which realizes this concept in an all-optical way obviating the need for image-processing. With the help of an additional intermediate optical beam expansion between descanning and a further rescanning of the detected light, an image with the advantages of photon reassignment can be acquired. However, just as in computational photon reassignment, a loss in confocal sectioning performance is caused by working with relatively open pinholes. The OPRA system shares properties such as flexibility and ease of use with a confocal laser scanning microscope, and is therefore expected to be of use for future biomedical routine research.