Local adsorption structure and bonding of porphine on Cu(111) before and after self-metalation

We have experimentally determined the lateral registry and geometric structure of free-base porphine (2H-P) and copper-metalated porphine (Cu-P) adsorbed on Cu(111), by means of energy-scanned photoelectron diffraction (PhD), and compared the experimental results to density functional theory (DFT) calculations that included van der Waals corrections within the Tkatchenko-Scheffler approach. Both 2H-P and Cu-P adsorb with their center above a surface bridge site. Consistency is obtained between the experimental and DFT-predicted structural models, with a characteristic change in the corrugation of the four N atoms of the molecule's macrocycle following metalation. Interestingly, comparison with previously published data for cobalt porphine adsorbed on the same surface evidences a distinct increase in the average height of the N atoms above the surface through the series 2H-P, Cu-P, cobalt porphine. Such an increase strikingly anti-correlates the DFT-predicted adsorption strength, with 2H-P having the smallest adsorption height despite the weakest calculated adsorption energy. In addition, our findings suggest that for these macrocyclic compounds, substrate-to-molecule charge transfer and adsorption strength may not be univocally correlated

Tracking interfacial changes of graphene/Ge(110) during in-vacuum annealing

Graphene quality indicators obtained by Raman spectroscopy have been correlated to the structural changes of the graphene/Germanium interface as a function of in-vacuum thermal annealing. Specifically, it is found that graphene becomes markedly defected at 650 {\deg}C. By combining scanning tunneling microscopy, x-Ray Photoelectron Spectroscopy and Near Edge x-ray Absorption Fine Structure Spectroscopy, we conclude that these defects are due to the release of H_{2} gas trapped at the graphene/Germanium interface. The H_{2} gas was produced following the transition from the as-grown hydrogen-termination of the Ge(110) surface to the emergence of surface reconstructions in the substrate. Interestingly, a complete self-healing process is observed in graphene upon annealing to 800 {\deg}C. The subtle interplay revealed between the microscopic changes occurring at the graphene/Germanium interface and graphene's defect density is valuable for advancing graphene growth, controlled 2D-3D heterogeneous materials interfacing and integrated fabrication technology on semiconductors

The crystal structure, chemical bonding, and magnetic properties of the intercalation compounds CrxZrTe2 (x = 0–0.3)

New intercalation compounds CrxZrTe2 were synthesized in the Cr concentration range of x = 0–0.3. A thorough study of the crystal and electronic structure has been performed. It was found that there is competition in the distribution of the Cr atoms over the octa- and tetrahedral sites in the van der Waals gap, depending on the Cr content. The ordering of the Cr atoms was found at x ≥ 0.25; at the same time, the lattice symmetry decreases from trigonal P-3m1 to monoclinic F2/m. This ordering stabilizes the octahedral coordination of the Cr atoms by Te atoms. The analysis of the experimental data on the electronic structure and DOS calculations showed that the Cr 3d states are spin-split. However, these Cr states are still overlapped by non-spin-split Zr and Te states. © 2021 Elsevier B.V.The research was carried out within the state assignment of Minobrnauki of Russia (theme “Electron” No. AAAA-A18-118020190098-5, theme “Spin” No. AAAA-A18-118020290104-2 and theme “Quantum” No. AAAA-A18-118020190095-4) and with partial financial support of the RFBR (project 20-03-00275). This work has been done using facilities of the Shared Service Centre “Ural-M”, Institute of Metallurgy of the Ural Branch of the Russian Academy of Sciences. The sample synthesis were performed within the RSF grant (project No.17-73-10219). I.P., and S.N. acknowledge funding from EUROFEL project (RoadMap Esfri). This project has received funding from the EU-H2020 research and innovation program under grant agreement No 654360 having benefitted from the Access provided by IOM-CNR in Trieste (Italy) within the framework of the NFFA-Europe Transnational Access Activity. We thank Federica Bondino and Elena Magnano for the kind support and we acknowledge the Elettra Sincrotrone Trieste for providing access to its synchrotron radiation facilities

Surface investigation and aluminum oxide estimation on test filters for the ATHENA X-IFU and WFI detectors

The ATHENA mission provides the demanded capabilities to address the ESA science theme "Hot and Energetic Universe". Two complementary instruments are foreseen: the X-IFU (X-ray Integral Field Unit) and WFI (Wide Field Imager). Both the instruments require filters to avoid that the IR radiation heats the X-IFU cryogenic detector and to protect the WFI detector from UV photons. Previous experience on XMM filters recommends to employ bilayer membrane consisting of aluminum deposited on polyimide. In this work, we use the X-ray Photoelectron Spectroscopy (XPS) to quantify the native aluminum oxide thickness that affects the spectral properties of the filter. The estimation of the oxide thickness of the prototype filter for ATHENA is a considerable information for the conceptual design of the filters. © (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only

Effects of thermal annealing on the structural and electronic properties of rare earth-implanted MoO3 nanoplates

The compositional, structural and morphological recovery of α-MoO nanoplates implanted with Eu and Er ions has been assessed as a function of post-implantation thermal treatments. Rapid thermal annealing induces the formation of phases different from α-MoO and seems to be unable to recover the original oxygen content of the nanostructures. In contrast, conventional annealing in air at 450 °C for 4 hours fully recovers the original molybdenum trioxide structure and leads to an effective optical activation of both Er and Eu ions. Synchrotron-based X-ray photoelectron spectroscopy and X-ray absorption studies confirm the incorporation of the rare earth ions into their trivalent charge state and reveal the modification of the original valence band structure of the nanoplates.This work has been supported by MINECO through projects MAT2012-31959, MAT2015-65274-R and CSD2009-0013. KL thanks FCT Portugal for her grant as “Investigador FCT”. CM acknowledges the financial support by the “Ramón y Cajal” Program of MINECO (RYC-2014-16626)