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

Characterization of multifunctional β-NaEuF4/NaGdF4 core–shell nanoparticles with narrow size distribution

We characterized NaEuF4/NaGdF4 core–shell nanoparticles

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

Supplementary material of “A ferromagnetic Eu-Pt surface compound grown below hexagonal boron nitride”

The supplementary information file contains: Supplementary Figures S1-S8. Supplementary information and data are provided to further illustrate the intercalation process of Eu below the hBN/Pt substrate as well as magnetic easy axis determination of the Eu-Pt alloy below hBN.Peer reviewe

A ferromagnetic Eu-Pt surface compound grown below hexagonal boron nitride

One of the fundamental applications for monolayer-thick 2D materials is their use as protective layers of metal surfaces and in situ intercalated reactive materials in ambient conditions. Here we investigate the structural, electronic, and magnetic properties, as well as the chemical stability in air of a very reactive metal, Europium, after intercalation between a hexagonal boron nitride (hBN) layer and a Pt substrate. We demonstrate that Eu intercalation leads to a hBN-covered ferromagnetic EuPt2 surface alloy with divalent Eu2+ atoms at the interface. We expose the system to ambient conditions and find a partial conservation of the di-valent signal and hence the Eu–Pt interface. The use of a curved Pt substrate allows us to explore the changes in the Eu valence state and the ambient pressure protection at different substrate planes. The interfacial EuPt2 surface alloy formation remains the same, but the resistance of the protecting hBN layer to ambient conditions is reduced, likely due to a rougher surface and a more discontinuous hBN coating.We acknowledge financial support from grants PID2020-116093RB-C44 funded by the Spanish MCIN/AEI/10.13039/501100011033 and the Basque Government (Grant IT-1591-22) as well as from the German BMBF (grant 05K19KER). We acknowledge the European Synchrotron Radiation Facility for provision of beam time on ID32. ESRF access was provided through proposal MA-5454.76 Part of the research leading to the results has been supported by the project CALIPSOplus under Grant Agreement 730872 from the EU Framework Programme for Research and Innovation HORIZON 2020. Y. H. appreciates the support of Japan Society for the Promotion of Science (JSPS) Overseas Research Fellowships and I. P. and F. B. acknowledge financial support from EUROFEL project (RoadMap Esfri).Peer reviewe