Jun Fujii is responsible of several instruments of sample growth and characterization within NFFA Laboratory.
His main scientific interest is to study electronic, magnetic and geometrical structures of surface and interfaces by means of photoelectron spectroscopy, photoabsorption spectroscopy, x-ray magnetic circular dichroism, STM and STS. The electronic and geometrical structures of magnetic materials are of particular interest.
Here, we present an integrated ultra-high vacuum apparatus—named MBE-Cluster —dedicated to the growth and in situ structural, spectroscopic, and magnetic characterization of complex materials. Molecular Beam Epitaxy (MBE) growth of metal oxides, e.g., manganites, and deposition of the patterned metallic layers can be fabricated and in situ characterized by reflection high-energy electron diffraction, low-energy electron diffraction, Auger electron spectroscopy, x-ray photoemission spectroscopy, and azimuthal longitudinal magneto-optic Kerr effect. The temperature can be controlled in the range from 5 K to 580 K, with the possibility of application of magnetic fields H up to ±7 kOe and electric fields E for voltages up to ±500 V. The MBE-Cluster operates for in-house research as well as user facility in combination with the APE beamlines at Sincrotrone-Trieste and the high harmonic generator facility for time-resolved spectroscopy.
From our users
Appl. Surf. Sci., 514, 145925, (2020)
Catalytic activity of PtSn4: Insights from surface-science spectroscopies
G. D'Olimpio, D.W. Boukhvalov, J. Fujii, P. Torelli, A. Marchionni, J. Filippi, C.-N. Kuo, R. Edla, L. Ottaviano, C.S. Lue, F. Vizza, S. Nappini, A. Politano
Bulk PtSn4 has recently attracted the interest of the scientific community for the presence of electronic states exhibiting Dirac node arcs, enabling possible applications in nanoelectronics. Here, by means of surface-science experiments and density functional theory, we assess its suitability for catalysis by studying the chemical reactivity of the (0 1 0)-oriented PtSn4 surface toward CO, H2O, O2 molecules at room temperature and, moreover, its stability in air. We demonstrate that the catalytic activity of PtSn4 is determined by the composition of the outermost atomic layer. Specifically, we find that the surface termination for PtSn4 crystals cleaved in vacuum is an atomic Sn layer, which is totally free from any CO poisoning. In oxygen-rich environment, as well as in ambient atmosphere, the surface termination is a SnOx skin including SnO and SnO2 in comparable amount. However, valence-band states, including those forming Dirac node arcs, are only slightly affected by surface modifications. The astonishingly beneficial influence of surface oxidation on catalytic activity has been demonstrated by electrocatalytic tests evidencing a reduction of the Tafel slope, from 442 down to 86 mV dec−1, whose origin has been explained by our theoretical model. The use of surface-science tools to tune the chemical reactivity of PtSn4 opens the way toward its effective use in catalysis, especially for hydrogen evolution reaction and oxygen evolution reaction.
From our users
Phys. Rev. B, 94, 075141, (2016)
Electronic structure of the chiral helimagnet and 3d-intercalated transition metal dichalcogenide Cr1/3NbS2
N. Sirica, S.-K. Mo, F. Bondino, I. Pis, S. Nappini, P. Vilmercati, J. Yi, Z. Gai, P.C. Snijders, P.K. Das, I. Vobornik, N. Ghimire, M.R. Koehler, L. Li, D. Sapkota, D.S. Parker, D.G. Mandrus and N. Mannella
The electronic structure of the chiral helimagnet Cr1/3NbS2 has been studied with core level and angle-resolved photoemission spectroscopy (ARPES). Intercalated Cr atoms are found to be effective in donating electrons to the NbS2 layers but also cause significant modifications of the electronic structure of the host NbS2 material. In particular, the data provide evidence that a description of the electronic structure of Cr1/3NbS2 on the basis of a simple rigid band picture is untenable. The data also reveal substantial inconsistencies with the predictions of standard density functional theory. The relevance of these results to the attainment of a correct description of the electronic structure of chiral helimagnets, magnetic thin films/multilayers, and transition metal dichalcogenides intercalated with 3d magnetic elements is discussed.
Strada Statale 14 - km 163,5 - 34149 Trieste, ITALY
ph. +39 040 3756487 fax +39 040 226767
NFFA is a Progetto Internazionale financed by MIUR through CNR
(Istituto Officina dei Materiali, Trieste) and Elettra-Sincrotrone Trieste
and managed by the Commissione NFFA chaired by Giorgio Rossi
(Università di Milano and IOM-CNR).