Electronic Structure of β-NaxV2O5 (x ≈ 0.33) Polycrystalline Films: Growth, Spectroscopy, and Theory

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• 作者：Bo Chen ; Jude Laverock ; Dave Newby ; Jr. ; Ting-Yi Su ; Kevin E. Smith ; Wei Wu ; Linda H. Doerrer ; Nicholas F. Quackenbush ; Shawn Sallis ; Louis F. J. Piper ; Daniel A. Fischer ; Joseph C. Woicik
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：January 16, 2014
• 年：2014
• 卷：118
• 期：2
• 页码：1081-1094
• 全文大小：754K
• ISSN：1932-7455

文摘

We present a detailed study of the microstructure and electronic structure of 尾-Na_xV₂O₅ (x 鈮?0.33) polycrystalline films, combining film growth, X-ray spectroscopies, and first-principles calculations. High-quality crystalline and stoichiometric V₂O₅ and 尾-Na_0.33V₂O₅ films were grown by a sol鈥揼el process, spin-coating, and rapid thermal annealing. The V₂O₅ film, which exhibits a rough surface, is preferentially oriented in the (001) direction perpendicular to the surface, whereas the b-axis of 尾-Na_0.33V₂O₅ is oriented in the substrate plane. The 尾-Na_0.33V₂O₅ film consists of a nested layered structure composed of single-crystalline rods of a few hundred nanometers in diameter and a few micrometers in length. Photoemission and X-ray absorption measurements of 尾-Na_0.33V₂O₅ confirm the Na incorporation and the presence of mixed V⁵⁺ and V⁴⁺ species and weakly occupied V 3d states. At the V L-edge, X-ray absorption and resonant inelastic X-ray measurements suggest a larger crystal field for 尾-Na_0.33V₂O₅ compared with isoelectronic 尾-Sr_0.17V₂O₅. We observe the lowest local crystal-field dd* transition at an energy of 鈭?.6 卤 0.1 eV for 尾-Na_0.33V₂O₅, which is substantially larger than 尾-Sr_0.17V₂O₅; this large difference is interpreted as arising from the stronger distortions to the VO₆ octahedra in 尾-Na_0.33V₂O₅.