Probing the structure of vanadium tetracyanoethylene using electron energy-loss spectroscopy
Probing the structure of vanadium tetracyanoethylene using electron energy-loss spectroscopy
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DOI：
10.1063/5.0087997
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发表时间：
2022-08
期刊：
影响因子：
6.1
通讯作者：
Amanda H. Trout;S. Kurfman;Yueguang Shi;M. Chilcote;M. Flatté;E. Johnston-Halperin;D. McComb
中科院分区：
文献类型：
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作者：
Amanda H. Trout;S. Kurfman;Yueguang Shi;M. Chilcote;M. Flatté;E. Johnston-Halperin;D. McComb
基于分子的亚铁磁半导体四氰乙烯钒（V[TCNE] x, x [公式：见正文]2）由于其优异的相干磁波特性和易于片上集成而引起了量子信息界的兴趣。尽管具有这些吸引人的特性，但由于缺乏详细的原子和电子结构信息，对长程磁有序的电子结构和机制的详细理解仍然难以捉摸。先前通过 X 射线吸收近边光谱和扩展 X 射线吸收精细结构的研究已经产生了各种提出的结构，一般来说，V[TCNE] x 被认为是八面体配位的 V2+ 的三维网络，每个与六个 TCNE 分子键合。在这里，我们通过将密度泛函理论（DFT）的计算与V[TCNE] x 薄膜的扫描透射电子显微镜和电子能量损失谱（EELS）相关联，阐明了V[TCNE] x 薄膜的电子结构、结构排序和降解途径。低损耗 EELS 测量揭示了与 DFT 模型定量一致的带隙和激发态结构，包括结构内顶端和赤道 TCNE 配体之间的能量分裂，提供了由驱动这些薄膜中强大磁有序的电子结构的理论描述直接支持的实验结果。铁损 EELS 证实了八面体配位的 V+2 原子的存在。氧化后，C1s-π* 峰的变化表明 TCNE 的 C=C 优先受到攻击。此外，我们发现随着电影的老化，结构顺序会放松。这些结果为更全面和基本地了解此类金属配体化合物的磁有序和动力学奠定了基础。
The molecule-based ferrimagnetic semiconductor vanadium tetracyanoethylene (V[TCNE] x, x [Formula: see text] 2) has garnered interest from the quantum information community due to its excellent coherent magnonic properties and ease of on-chip integration. Despite these attractive properties, a detailed understanding of the electronic structure and mechanism for long-range magnetic ordering have remained elusive due to a lack of detailed atomic and electronic structural information. Previous studies via x-ray absorption near edge spectroscopy and the extended x-ray absorption fine structure have led to various proposed structures, and in general, V[TCNE] x is believed to be a three-dimensional network of octahedrally coordinated V2+, each bonded to six TCNE molecules. Here, we elucidate the electronic structure, structural ordering, and degradation pathways of V[TCNE] x films by correlating calculations of density functional theory (DFT) with scanning transmission electron microscopy and electron energy-loss spectroscopy (EELS) of V[TCNE] x films. Low-loss EELS measurements reveal a bandgap and an excited state structure that agree quantitatively with DFT modeling, including an energy splitting between apical and equatorial TCNE ligands within the structure, providing experimental results directly backed by theoretical descriptions of the electronic structure driving the robust magnetic ordering in these films. Core-loss EELS confirms the presence of octahedrally coordinated V+2 atoms. Upon oxidation, changes in the C1s- π* peak indicate that C=C of TCNE is preferentially attacked. Furthermore, we identify a relaxation of the structural ordering as the films age. These results lay the foundation for a more comprehensive and fundamental understanding of magnetic ordering and dynamics in these classes of metal–ligand compounds.