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HAXPES Systems

Hard X-ray Photoelectron Spectroscopy (HAXPES) can be performed either at synchrotrons or with laboratory sources, like the µFOCUS 730 HE monochromator. The analyzers require higher voltages, making special power supplies and detectors necessary. Optimized geometries are needed for high count rates. A combination with standard X-ray sources is attractive. By this, users are able to perform surface and bulk sensitive measurements at the same sample.

RELATED PRODUCTS

PUBLICATIONS

  1. (2021) <p>A comparative study of electrochemical cells for in situ x-ray spectroscopies in the soft and tender x-ray range</p>

    n situ x-ray spectroscopies offer a powerful way to understand the electronic structure of the electrode–electrolyte interface under operating conditions. However, most x-ray techniques require vacuum, making it necessary to design spectro-electrochemical cells with a delicate interface to the wet electrochemical environment. The design of the cell often dictates what measurements can be done and which electrochemical processes can be studied. Hence, it is important to pick the right spectro-electrochemical cell for the process of interest. To facilitate this choice, and to highlight the challenges in cell design, we critically review four recent, successful cell designs. Using several case studies, we investigate the opportunities and limitations that arise in practical experiments.



    J.-J. Velasco-Vélez, L. J. Falling, D. Bernsmeier, M. J Sear, P. C. J. Clark, T.-S. Chan, E. Stotz, M. Hävecker, R. Kraehnert, and A. Knop-Gericke
    Juan-Jesús Velasco-Vélez et al 2021 J. Phys. D: Appl. Phys. 54 124003
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  2. (2021) <p>In situ investigation of the bismuth vanadate/potassium phosphate interface reveals morphological and composition dependent light-induced surface reactions</p>

    Bismuth vanadate (BiVO4) is an established n-type oxide semiconductor for photoelectrochemical oxygen evolution. Direct charge carrier recombination at the solid/liquid interface is a major cause of efficiency loss in BiVO4-based devices. Intrinsic and extrinsic surface states (SSs) can act as electron and hole traps that enhance the recombination rate and lower the faradaic efficiency. In this study, we investigate the BiVO4/aqueous KPi interface using two types of samples. The samples were prepared at two different deposition and annealing temperatures (450 °C and 500 °C) leading to different morphologies and stoichiometries for the two samples. Both samples exhibit SSs in the dark that are passivated under illumination. In situ ambient pressure hard x-ray photoelectron spectroscopy experiments performed under front illumination conditions reveal the formation of a bismuth phosphate (BiPO4) surface layer for the sample annealed at 450 °C, whereas the sample annealed at 500 °C exhibits band flattening without the formation of BiPO4. These results imply that the light-induced formation of BiPO4 may not be responsible for SS passivation. Our study also suggests that slight differences in the synthesis parameters lead to significant changes in the surface stoichiometry and morphology, with drastic effects on the physical-chemical properties of the BiVO4/electrolyte interface. These differences may have important consequences for device characteristics such as long-term stability.



    M. Favaro, I.Y. Ahmet, P. C. J. Clark, F. F. Abdi, M. J. Sear, R. van de Krol, and D. E. Starr
    Marco Favaro et al 2021 J. Phys. D: Appl. Phys. 54 164001
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  3. (2021) <p>Spectroscopic analysis with tender X-rays: SpAnTeX, a new AP-HAXPES end-station at BESSY II</p>

    We present a newly developed end-station at BESSY II dedicated to in situ Spectroscopic Analysis with Tender X-rays (SpAnTeX). The core of the end-station is a new SPECS PHOIBOS 150 HV NAP electron spectrometer. First, we show that the system has successfully achieved high electron transmission and detection efficiency under gas pressures up to 30 mbar and photon energies ranging between 200 eV and 10 keV. Second, using two features of this spectrometer (a new lateral resolution lens and a 3D delay line detector), we show that the endstation enables collection of the photoelectron spatial distribution under realistic working conditions (p ≥ 20 mbar) with a resolution better than 30 μm and the possibility to perform time resolved studies using a continuous tender X-ray source. We conclude by reporting an example of the possible experiments that can be performed using this new endstation using the Dip-and-Pull technique.

    Although mainly focused on the characterization of solid/liquid interfaces using AP-HAXPES, the end-station can be used at soft X-ray beamlines for more traditional AP-XPS experiments. The Dip-and-Pull module also demonstrates good electrochemical performance. The wide pressure and photon energy range covered by this end-station also enables investigations of solid/solid, solid/gas, liquid/vapor and liquid/liquid interfaces at pressures up to 30 mbar with tender X-rays.



    M. Favaro, P. C. J. Clark, M. J. Sear, M. Johansson, S. Maehl, R. van de Krol, and D.E. Starr
    Surface Science
    Volume 713, November 2021, 121903
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