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Open AccessArticle

Structural Evolution of MoO3 Thin Films Deposited on Copper Substrates upon Annealing: An X-ray Absorption Spectroscopy Study

1
Department of Physics, Università di Roma Tor Vergata, via della Ricerca Scientifica 1, 00133 Rome, Italy
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Istituto Nazionale Fisica Nucleare, Laboratori Nazionali di Frascati, via Enrico Fermi 40, 00044 Frascati, Italy
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Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, UK
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Istituto Nazionale Fisica Nucleare, Sezione di Milano, Via Celoria 16, 20133 Milano, Italy
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Rome International Centre for Material Science Superstripes, RICMASS, via dei Sabelli 119A, 00185 Rome, Italy
*
Author to whom correspondence should be addressed.
Condens. Matter 2019, 4(2), 41; https://doi.org/10.3390/condmat4020041
Received: 14 March 2019 / Revised: 13 April 2019 / Accepted: 15 April 2019 / Published: 18 April 2019
(This article belongs to the Special Issue High Precision X-Ray Measurements)
Structural changes of MoO3 thin films deposited on thick copper substrates upon annealing at different temperatures were investigated via ex situ X-Ray Absorption Spectroscopy (XAS). From the analysis of the X-ray Absorption Near-Edge Structure (XANES) pre-edge and Extended X-ray Absorption Fine Structure (EXAFS), we show the dynamics of the structural order and of the valence state. As-deposited films were mainly disordered, and ordering phenomena did not occur for annealing temperatures up to 300 °C. At ~350 °C, a dominant α-MoO3 crystalline phase started to emerge, and XAS spectra ruled out the formation of a molybdenum dioxide phase. A further increase of the annealing temperature to ~500 °C resulted in a complex phase transformation with a concurrent reduction of Mo6+ ions to Mo4+. These original results suggest the possibility of using MoO3 as a hard, protective, transparent, and conductive material in different technologies, such as accelerating copper-based devices, to reduce damage at high gradients. View Full-Text
Keywords: molybdenum; TM oxides; XAFS; thin films molybdenum; TM oxides; XAFS; thin films
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Macis, S.; Rezvani, J.; Davoli, I.; Cibin, G.; Spataro, B.; Scifo, J.; Faillace, L.; Marcelli, A. Structural Evolution of MoO3 Thin Films Deposited on Copper Substrates upon Annealing: An X-ray Absorption Spectroscopy Study. Condens. Matter 2019, 4, 41.

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