Condens. Matter 2017, 2(4), 38; https://doi.org/10.3390/condmat2040038
Nanoscale Phase Separation and Lattice Complexity in VO2: The Metal–Insulator Transition Investigated by XANES via Auger Electron Yield at the Vanadium L23-Edge and Resonant Photoemission
Augusto Marcelli 1,2,3,*
, Marcello Coreno 3, Matus Stredansky 4,5, Wei Xu 2,6, Chongwen Zou 7, Lele Fan 8, Wangsheng Chu 7, Shiqiang Wei 7, Albano Cossaro 5, Alessandro Ricci 2, Antonio Bianconi 2,9,10 and Alessandro D’Elia 4,5
, Marcello Coreno 3, Matus Stredansky 4,5, Wei Xu 2,6, Chongwen Zou 7, Lele Fan 8, Wangsheng Chu 7, Shiqiang Wei 7, Albano Cossaro 5, Alessandro Ricci 2, Antonio Bianconi 2,9,10 and Alessandro D’Elia 4,5
1
Laboratori Nazionali di Frascati, Istituto Nazionale di Fisica Nucleare, 00044 Frascati, Italy
2
RICMASS, Rome International Center for Materials Science Superstripes, Via dei Sabelli 119A, 00185 Rome, Italy
3
ISM-CNR, Istituto Struttura della Materia, LD2 Unit, Basovizza Area Science Park, 34149 Trieste, Italy
4
Department of Physics, University of Trieste, Via A. Valerio 2, 34127 Trieste, Italy
5
IOM-CNR, Laboratorio Nazionale TASC, Basovizza SS-14, km 163.5, 34012 Trieste, Italy
6
Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Beijing 100049, China
7
National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230026, China
8
Key Laboratory for Advanced Technology in Environmental Protection of Jiangsu Province, Yancheng Institute of Technology, Yancheng 224051, China
9
IC-CNR, Istituto di Cristallografia, Via Salaria km 29, 00015 Roma, Italy
10
National Research Nuclear University Mephi, Kashirskoe shosse 31, 115409 Moscow, Russia
*
Author to whom correspondence should be addressed.
Received: 28 September 2017 / Revised: 27 November 2017 / Accepted: 7 December 2017 / Published: 10 December 2017
(This article belongs to the Special Issue Control and Enhancement of Quantum Coherence in Nanostructured Materials)
Abstract
Among transition metal oxides, VO2 is a particularly interesting and challenging correlated electron material where an insulator to metal transition (MIT) occurs near room temperature. Here we investigate a 16 nm thick strained vanadium dioxide film, trying to clarify the dynamic behavior of the insulator/metal transition. We measured (resonant) photoemission below and above the MIT transition temperature, focusing on heating and cooling effects at the vanadium L23-edge using X-ray Absorption Near-Edge Structure (XANES). The vanadium L23-edges probe the transitions from the 2p core level to final unoccupied states with 3d orbital symmetry above the Fermi level. The dynamics of the 3d unoccupied states both at the L3- and at the L2-edge are in agreement with the hysteretic behavior of this thin film. In the first stage of the cooling, the 3d unoccupied states do not change while the transition in the insulating phase appears below 60 °C. Finally, Resonant Photoemission Spectra (ResPES) point out a shift of the Fermi level of ~0.75 eV, which can be correlated to the dynamics of the 3d// orbitals, the electron–electron correlation, and the stability of the metallic state. View Full-TextKeywords:
vanadium dioxide; resonant photoemission; metal–insulator transition; XANES; Auger electron yield; strained film; phase separation
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Marcelli, A.; Coreno, M.; Stredansky, M.; Xu, W.; Zou, C.; Fan, L.; Chu, W.; Wei, S.; Cossaro, A.; Ricci, A.; Bianconi, A.; D’Elia, A. Nanoscale Phase Separation and Lattice Complexity in VO2: The Metal–Insulator Transition Investigated by XANES via Auger Electron Yield at the Vanadium L23-Edge and Resonant Photoemission. Condens. Matter 2017, 2, 38.
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