Giancarlo Panaccione has a Permanent Position as beamline scientist of the APE beamline at INFM (now CNR) since 1998 (Senior Researcher since 2011) and is responsible of the SPRINT Laboratory high harmonic generation beamline.
His present research interests are focused on the electronic and magnetic properties of quantum materials and nanomaterials. In particular, the activity is focused on achieving control of these properties via external tuning parameters, growth and fabrication of nanoscale heterostructures, possibly leading to new applications in quantum electronics and spintronics. His research activity is mostly devoted to the exploitation of Synchrotron Radiation spectroscopies for the study of correlated systems and novel quantum materials, following three main axes: (1) electronic and magnetic properties of low dimensional sys- tems (surfaces and interfaces), (2) electron confinement, and (3) complex oxides.
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.
Phys. Rev. Materials, 4, 025801, (2020)
Distinct behavior of localized and delocalized carriers in anatase TiO2 (001) during reaction with O2
C. Bigi, Z. Tang, G.M. Pierantozzi, P. Orgiani, P. K. Das, J. Fujii, I. Vobornik, T. Pincelli, A. Troglia, T.-L. Lee, R. Ciancio, G. Drazic, A. Verdini, A. Regoutz, P.D.C. King, D. Biswas, G. Rossi, G. Panaccione, and A. Selloni
Two-dimensional (2D) metallic states induced by oxygen vacancies (VOs) at oxide surfaces and interfaces provide opportunities for the development of advanced applications, but the ability to control the behavior of these states is still limited. We used angle resolved photoelectron spectroscopy combined with density-functional theory (DFT) to study the reactivity of VO-induced states at the (001) surface of anatase TiO2, where both 2D metallic and deeper lying in-gap states (IGs) are observed. The 2D and IG states exhibit remarkably different evolutions when the surface is exposed to molecular O2: while IGs are almost completely quenched, the metallic states are only weakly affected. DFT calculations indeed show that the IGs originate from surface VOs and remain localized at the surface, where they can promptly react with O2. In contrast, the metallic states originate from subsurface vacancies whose migration to the surface for recombination with O2 is kinetically hindered on anatase TiO2 (001), thus making them much less sensitive to oxygen dosing.
Phys. Rev. Materials, 4, 025006, (2020)
Direct insight into the band structure of SrNbO3
C. Bigi, P. Orgiani, J. Slawinska, J. Fujii, J.T. Irvine, S. Picozzi, G. Panaccione, I. Vobornik, G. Rossi, D. Payne, and F. Borgatti
We present the results of a photon energy and polarization dependent angle-resolved photoemission spectroscopy (ARPES) study on high quality, epitaxial SrNbO3 thin films prepared in situ by pulsed laser deposition (PLD). We show that the Fermi surface is composed of three bands mainly due to t(2g) orbitals of Nb 4d, in analogy with the 3d-based perovskite systems. The bulk band dispersion for the conduction and valence states obtained by density functional theory (DFT) is generally consistent with the ARPES data. The small discrepancy in the bandwidth close to the Fermi level seems to result from the interplay of correlation effects and the presence of vacancies. The ARPES results are complemented by soft x-ray photoemission spectroscopy measurements in order to provide indications on the chemical states and the stoichiometry of the material.
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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).