VO2 is one of the most studied vanadium oxides because it undergoes a reversible metal-insulator transition (MIT) upon heating with a critical temperature of around 340 K. One of the most overlooked aspects of VO2 is the band’s anisotropy in the metallic phase when the Fermi level is crossed by two bands: π* and d||. They are oriented perpendicularly in one respect to the other, hence generating anisotropy. One of the parameters tuning MIT properties is the unbalance of the electron population of π* and d|| bands that arise from their different energy position with respect to the Fermi level. In systems with reduced dimensionality, the electron population disproportion is different with respect to the bulk leading to a different anisotropy. Investigating such a system with a band-selective spectroscopic tool is mandatory. In this manuscript, we show the results of the investigation of a single crystalline 8 nm VO2/TiO2(101) film. We report on the effectiveness of linearly polarized resonant photoemission (ResPES) as a band-selective technique probing the intrinsic anisotropy of VO2.
From our users
Phys. Rev. Materials, 5, 104403, (2021)
Identification of hidden orbital contributions in the La0.65Sr0.35MnO3 valence band
F. Offi, K. Yamauchi, S. Picozzi, V. Lollobrigida, A. Verna, C. Schlueter, T.-L. Lee, A. Regoutz, D. J. Payne, A. Petrov, G. Vinai, G. M. Pierantozzi, T. Pincelli, G. Panaccione, and F. Borgatti
Hybridization of electronic states and orbital symmetry in transition metal oxides are generally considered key ingredients in the description of both their electronic and magnetic properties. In the prototypical case of La0.65Sr0.35MnO3 (LSMO), a landmark system for spintronics applications, a description based solely on Mn 3d and O 2p electronic states is reductive. We thus analyzed elemental and orbital distributions in the LSMO valence band through a comparison between density functional theory calculations and experimental photoelectron spectra in a photon energy range from soft to hard x rays. We reveal a number of hidden contributions, arising specifically from La 5p, Mn 4s, and O 2s orbitals, considered negligible in previous analyses; our results demonstrate that all these contributions are significant for a correct description of the valence band of LSMO and of transition metal oxides in general.
NFFA Thesis
University of Milan Master's Degree Thesis, (2021)
Transient grating spectroscopy with a magnetic probe: a study on phonon-driven magnons in a ferromagnetic thin film
M. Brioschi (Supervisors: G. Rossi, G. Panaccione, R. Cucini)
Materials and heterostructures that exhibit coupling between elastic and magnetic degrees of freedom are of both fundamental and technological interest. In particular, they have great potential for novel energy-efficient spintronic devices because acoustic waves can generate coherent and long-living spin waves through inverse magnetostriction, which consists in variations in the magnetization due to lattice deformations. As optical methods are versatile, non-invasive and contactless, an all-optical approach has been implemented and applied to study magnetoelastic coupling in a ferromagnetic film on a glass substrate. The present thesis work was performed at the NFFA-SPRINT facility of IOM-CNR in the Fermi@Elettra hall at Trieste, where I actively contributed to the realization and characterization of an all new experimental setup which is able to combine transient grating spectroscopy with a time-resolved Faraday polarimetry.
From our users
J. Elec. Spectr. Rel. Phenom., 146902, (2019)
Operando photoelectron emission spectroscopy and microscopy at Elettra soft X-ray beamlines: From model to real functional systems
M. Amati, V. Bonanni, L. Braglia, F. Genuzio, L. Gregoratti, M. Kiskinova, A. Kolmakov, A. Locatelli, E. Magnano, A.A. Matruglio, T.O. Menteş, S. Nappini, P. Torelli, P. Zeller
Implementation of in-situ and operando experimental set-ups for bridging the pressure gap in characterization techniques based on monitoring of photoelectron emission has made significant achievements at several beamlines at Elettra synchrotron facility. These set-ups are now operational and have been successfully used to address unsolved issues exploring events occurring at solid–gas, solid–liquid and solid-solid interfaces of functional materials. The sections in the article communicate the research opportunities offered by the current set-ups at APE, BACH, ESCAmicroscopy and Nanospectroscopy beamlines and outline the next steps to overcome the present limits.
From our users
J. Vac. Sci. Technol. B, 37, 061209, (2019)
Transparent conductive oxide-based architectures for the electrical modulation of the optical response: A spectroscopic ellipsometry study
M. Sygletou, F. Bisio, S. Benedetti, P. Torelli, A. di Bona, A. Petrov, and M. Canepa
Transparent conductive oxides are a class of materials that combine high optical transparency with high electrical conductivity. This property makes them uniquely appealing as transparent conductive electrodes in solar cells and interesting for optoelectronic and infrared-plasmonic applications. One of the new challenges that researchers and engineers are facing is merging optical and electrical control in a single device for developing next-generation photovoltaic, optoelectronic devices and energy-efficient solid-state lighting. In this work, the authors investigated the possible variations in the dielectric properties of aluminum-doped ZnO (AZO) upon gating by means of spectroscopic ellipsometry (SE). The authors investigated the electrical-bias-dependent optical response of thin AZO films fabricated by magnetron sputtering within a parallel-plane capacitor configuration. The authors address the possibility to control their optical and electric performances by applying bias, monitoring the effect of charge injection/depletion in the AZO layer by means of in operando SE versus applied gate voltage.
From our users
OSA Technical Digest, paper EW2B.5, (2018)
A Novel High Order Harmonic Source for Time- and Angle-Resolved Photoemission Experiments
P. Miotti, F. Cilento, R. Cucini, A. De Luisa, A. Fondacaro, F. Frassetto, D. Kopić, D. Payne, A. Sterzi, T. Pincelli, G. Panaccione, F. Parmigiani, G. Rossi, and L. Poletto
The design and characterization of a HHG source conceived for Time and Angle Resolved PhotoElectron Spectroscopy (TR-ARPES) experiments are presented. The harmonics are selected through a grating monochromator with an innovative design able to provide XUV radiation for two distinct TR-ARPES setups.
From our users
Chemical Physics Letters, 683. 135, (2017)
Time resolved resonant photoemission study of energy level alignment at donor/acceptor interfaces
R. Costantini, T. Pincelli, A. Cossaro, A. Verdini, A. Goldoni, S. Cichoň, M. Caputo, M.Pedio, G. Panaccione, M.G. Silly, F. Sirotti, A. Morgante, M. Dell'Angela
The knowledge of the picosecond dynamics of the energy level alignment between donor and acceptor materials in organic photovoltaic devices under working conditions is a challenge for fundamental material research. We measured by means of time-resolved Resonant X-ray Photoemission Spectroscopy (RPES) the energy level alignment in ZnPc/C60 films. We employed 800 nm femtosecond laser pulses to pump the system simulating sunlight excitation and X-rays from the synchrotron as a probe. We measured changes in the valence bands due to pump induced modifications of the interface dipole. Our measurements prove the feasibility of time-resolved RPES with high repetition rate sources.
NFFA Thesis
University of Milan PhD Thesis, (2017)
Probing electron correlation dynamics: a multi-technique study applied to the half-metallic oxide La3-xSrxMnO5
This thesis completes my work as doctoral student of the Scuola di Dottorato in Fisica, Astrofisica e Fisica Applicata at the Università degli Studi di Milano that has been carried out, starting in November 4236, mostly at the Laboratorio TASC of IOM-CNR3 in the premises of the Elettra - Sincrotrone Trieste and FERMI@Elettra infrastructures4, in the framework of the NFFA and APE-beamline facilites5, as well as by accessing international large scale infrastructures and laboratories. The activity has addressed the development of experimental methodologies and novel instrumentation oriented to the study of the dynamical properties of highly correlated materials after high energy excitation. The science programme has been carried out by exploiting ultrafast femtosecond probes from the optical regime (Ti-Sa lasers, fibre laser oscillators) to the extreme UV-soft X rays at FERMI, to the picosecond hard X-rays from the SPring-: and Diamond synchrotron radiation source. The sample synthesis of correlated oxides and its characterization has been performed within the NFFA facility and APE-group collaboration in Trieste as well as the design and construction of the all new laser High Harmonic Generation beam line NFFA-SPRINT and its end station for time resolved vectorial electron spin polarimetry.
NFFA Thesis
University of Modena and Reggio Emilia Master's Thesis, (2014)
Towards Spin-resolved/Time-resolved Photoelectron Spectroscopy at the fs time scale: construction and commissioning of the ULTRASPIN apparatus
This thesis reports on the construction and commissioning tests of the novel experimental set-up needed for a long term research project, named ULTRASPIN, aiming at establishing time resolved spin-resolved photoemission measurements with ultra-short (10−14 s) photon pulses from Free Electron Laser beamlines or from table-top UV/Soft-X beamlines.
The ULTRASPIN project started in the summer 2013, building on competences and instrumentation in part available from the APE-beamline group of IOM-CNR at Elettra, and with the partial support of an European contract (EXSTASY-EXperimental STation for the Analysis of the Spin Dynamics, Grant agreement N.PIIF-GA-2012-326641) and related fellowship of a world-expert of Mott scattering.
I have been involved from the beginning in the final design, in the construction and commissioning of a novel stray-field free UHV apparatus for preparing and hosting atomically clean surfaces and for measuring the spin-polarization of the photo-emitted electrons with “single pulse” sensitivity down to the 10−14 s time scale, as well as in the standard high frequency spectroscopy mode. In the commissioning phase I have participated to test experiments on ULTRASPIN as well as to relevant experiments conducted in other apparatuses.
Login
You're being redirected, please wait few moments...