Unveiling the Electronic Structure of Pseudotetragonal WO 3 Thin Films
Résumé
WO3 is a binary 5d compound which has attracted remarkable attention due to the vast array of structural transitions that it undergoes in its bulk form. In the bulk, a wide range of electronic properties has been demonstrated, including metal-insulator transitions and superconductivity upon doping. In this context, the synthesis of WO3 thin films holds considerable promise for stabilizing targeted electronic phase diagrams and embedding them in technological applications. However, to date, the electronic structure of WO 3 thin films is experimentally unexplored, and only characterized by numerical calculations. Underpinning such properties experimentally would be important to understand not only the collective behavior of electrons in this transition-metal oxide, but also to explain and engineer both the observed optical responses to carriers' concentration and its prized catalytic activity. Here, by means of tensile strain, we stabilize WO3 thin films into a stable phase, which we call pseudo-tetragonal, and we unveil its electronic structure by combining photoelectron spectroscopy and density functional theory calculations. This study constitutes the experimental demonstration of the electronic structure of WO3 thin-films and allows us to pin down the first experimental benchmarks of the fermiology of this system.
Controlling the electronic properties of quantum systems allows us to realize technological applications with improved performance, stability, and durability, as well as significantly lower dissipation [1-3]. This is particularly relevant for 5d-based transition metal oxides, which might provide a platform for integration into existing technology, with improved current densities, enhanced electrochromic and photovoltaic responses, and reduced switching energies [4-12]. Therefore, understanding the electronic structure of quantum systems is a crucial task, especially for newly synthesized materials, and it allows to pin down the hallmarks that describe their conductivity, their Fermi surfaces, and the relationship of the latter with symmetries and crystal structure.
Here, by using pulsed laser deposition (PLD) [13-15], we exploit epitaxial strain to synthesize a thermally stable phase in thin films of the 5d compound WO3 (on a LaAlO3 substrate, LAO) and, by using angle-resolved photoelectron spectroscopy (ARPES), we unveil the electronic structure
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