Physical properties of epitaxial SrMnO 2.5−δ F γ oxyfluoride films
Physical properties of epitaxial SrMnO 2.5−δ F γ oxyfluoride films
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外延SrMnO 2.5-δ F γ氟氧化物薄膜的物理性能
DOI：
10.1088/1361-648x/ab2414
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
May, Steven J
中科院分区：
文献类型：
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作者：
Wang, Jiayi;Shin, Yongjin;Gauquelin, Nicolas;Yang, Yizhou;Lee, Christopher;Jannis, Daen;Verbeeck, Johan;Rondinelli, James M;May, Steven J
近年来，通过阴离子取代来修饰外延钙钛矿氧化物的电子性能，取代了常用的阳离子取代，成为掺杂外延钙钛矿氧化物的一种替代方法。本文以聚四氟乙烯为氟源，通过对srmno2.5薄膜进行拓扑氟化，制备了外延氧化氟化srmno2.5−δ F γ薄膜。制备了氧化srmno3薄膜，并与氟化样品进行了比较。通过调整氟化条件，系统地控制了x射线光发射光谱探测的F含量。电子输运测量表明，增加的F含量（高达γ= 0.14）系统地增加了电阻率，尽管在这些薄膜中F取代O引起了名义上的电子掺杂。相反，氧化后的srmno3表现出电阻率和传导活化能的降低。随着F含量的增加，光学吸收特征发生蓝移。密度泛函理论计算表明，F作为电子输运的散射中心，控制了观察到的薄膜的弱铁磁行为，降低了锰酸盐薄膜的带间光学跃迁。这些结果与大量电子掺杂的La 1−x Ce x mno3形成对比，说明了共价阴离子取代如何产生与具有相同标称b位氧化态的a位取代钙钛矿不同的物理行为。
Recently, topotactic fluorination has become an alternative way of doping epitaxial perovskite oxides through anion substitution to engineer their electronic properties instead of the more commonly used cation substitution. In this work, epitaxial oxyfluoride SrMnO 2.5− δ F γ films were synthesized via topotactic fluorination of SrMnO 2.5 films using polytetrafluoroethylene as the fluorine source. Oxidized SrMnO 3 films were also prepared for comparison with the fluorinated samples. The F content, probed by x-ray photoemission spectroscopy, was systematically controlled by adjusting fluorination conditions. Electronic transport measurements reveal that increased F content (up to γ= 0.14) systematically increases the electrical resistivity, despite the nominal electron-doping induced by F substitution for O in these films. In contrast, oxidized SrMnO 3 exhibits a decreased resistivity and conduction activation energy. A blue-shift of optical absorption features occurs with increasing F content. Density functional theory calculations indicate that F acts as a scattering center for electronic transport, controls the observed weak ferromagnetic behavior of the films, and reduces the inter-band optical transitions in the manganite films. These results stand in contrast to bulk electron-doped La 1− x Ce x MnO 3, illustrating how aliovalent anionic substitutions can yield physical behavior distinct from A-site substituted perovskites with the same nominal B-site oxidation states.