The XAFS-DET work package of the European LEAPS-INNOV project is developing a high-purity Germanium detectors for synchrotron applications requiring spectroscopic-grade response. The detectors integrate three key features: (1) newly designed monolithic Germanium sensors optimised to mitigate charge-sharing events, (2) an improved cooling and mechanical design structure supported by thermal simulations, and (3) complete electronic chain featuring a low-noise CMOS technology-based preamplifier. enabling high X-ray count rate capability over a broad energy range (5-100 keV). This paper discusses the first integration and characterization of one of the two multi-element Ge detectors at the European Synchrotron Radiation Facility (ESRF). The integration phase included validating high-throughput front-End electronics, integrating them with the Ge sensor, and operating them at liquid nitrogen temperature, in addition to the experimental characterization, which consists of electronics noise study and spectroscopic performance evaluation.
Palladium diselenide (PdSe2) is a two-dimensional (2D) transition metal dichalcogenide van der Waals material that exhibits a unique wrinkled pentagonal structure that results in strong anisotropic layer-dependent properties. Owing to these unique properties the material has a great potential for applications in electronic, optoelectronic, photonic and thermoelectric devices. Here, we study the electronic properties of monolayer (ML) PdSe2 in a Schottky junction by contacting the material with a tungsten scanning tunneling microscope (STM) tip. The STM-induced lifting of the 2D layer leads to structural warping of the top layer, which causes significant changes in the electronic properties of PdSe2 as well as the electrostatic potential across the junction. We compare the STM-determined work function of the warped PdSe2 ML with the work function of bulk PdSe2 as obtained by Kelvin probe force microscopy and electronic structure obtained by synchrotron-based angle-resolved photoemission spectroscopy, and x-ray photoelectron spectroscopy.
Tailoring the electronic properties of graphene is crucial for a variety of applications. In this study, we investigate the graphene growth on the high Miller-index, anisotropic Ir(311) surface, where it self-organizes into one-dimensional ripples accompanied by a short-wavelength, two-dimensional wave pattern that is spatially confined between them. By employing a combination of spectroscopy- and microscopy-based techniques, we show that carbon atoms on the ripples interact weakly with the substrate, whereas those in the flatter region between two ripples experience stronger interaction with iridium atoms, leading to a partial rehybridization of carbon orbitals towards sp3 character. Complementary density functional theory calculations identify at least three distinct families of non-equivalent carbon atoms within the graphene layer and reveal that atoms on ripples are subjected to compressive strain. Since both compressive strain and corrugation are key factors in influencing graphene's chemical reactivity, the coexistence of two different wave pattern on graphene/Ir(311) system points to a region-specific reactivity. This spatial modulation of properties offers exciting potential for the design of bifunctional catalysts, particularly for hydrogen storage applications and for advanced materials in spintronic.
Performances in micro-X-ray absorption near edge spectroscopy at the TwinMic beamline on biological specimens; a more comprehensive analytical tool for the biology community.
This study investigates the potential use of volcanic ash (VA) material from Mount Cameroon as an adsorbent for the removal of selenium (VI) from contaminated solutions. Selenium-sorbed materials were synthesized via a batch adsorption method, and the resulting samples were characterized using scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray absorption spectroscopy (XAS). The results suggest that Se-sorbed VA material can adopt the local structure of CaSeO3 and its chemical composition was associated with CaSeO3, Na2SeO3, and Na2SeO4. The adsorption mechanisms were related to ion exchange, adsorption, and chemical reduction. Langmuir model was found to be suitable for the adsorption data indicating that the surface of VA adsorbent presents monolayer and homogeneous actives sites. XAS technique could be applied to track changes in oxidation state, resolve the adsorption mechanism, and identify the chemical species and local structure of the sorbed element in the adsorbent material.
