AI 中文总结
本研究拓展拓扑转化法，从GaAs、AlAs等III-V族半导体合成两种新型Zintl薄膜及对应纳米线，其带隙、磁性质显示出热电、自旋电子学等应用潜力。
AI 中文摘要
Zintl相因具有多样的结构、磁性、热电、拓扑及光学性质而受到广泛关注。近期，研究人员通过分子束外延技术，利用纤锌矿型和闪锌矿型InAs纳米线的拓扑转化，合成了具有轴子磁拓扑特性的Zintl相Eu₃In₂As₄和Eu₅In₂As₆纳米线。本研究拓展了该方法，证明拓扑互扩散生长不仅适用于InAs之外的更多III-V族半导体，还可用于将三维衬底表面转化为Zintl薄膜及纳米线。我们报道两种新化合物的生长：从GaAs衬底转化得到Eu₅Ga₂As₆薄膜，从AlAs薄膜转化得到Eu₅Al₂As₆薄膜；同时将纤锌矿型和闪锌矿型GaAs纳米线转化为Eu₅Ga₂As₆纳米线。尽管其化学计量比与此前报道的Eu₅In₂As₆相同，但显微镜和衍射分析显示其为单一相的Pnma空间群而非Pbam，凸显了对称性导向的拓扑途径可构建新型Zintl骨架。这些化合物具有复杂的磁相图，包含三个磁转变，包括两种不同的反铁磁序，以及在施加磁场下通过自旋翻转转变演变为另一种反铁磁相的倾斜反铁磁相。从头算预测两种Zintl相均为半导体，Eu₅Ga₂As₆的带隙为0.79 eV，Eu₅Al₂As₆的带隙为0.90 eV。较低的对称性和更高的结构复杂性表明其晶格热导率被抑制，兼具热电应用潜力，以及在自旋电子学和探测器技术中的应用前景。本研究提供了一种与外延兼容的路线，可直接从相关III-V族半导体中发现并集成磁性Zintl薄膜和纳米线。
英文摘要
Zintl phases draw broad interest for their diverse structural, magnetic, thermoelectric, topological and optical properties. Recently, Zintl Eu$_3$In$_2$As$_4$ and Eu$_5$In$_2$As$_6$ nanowires with axion magneto-topology have been synthesized by molecular beam epitaxy via topotactic conversion of InAs wurtzite and zincblende nanowires. Here we extend this methodology, demonstrating that topotaxial mutual-exchange growth applies not only to a broader set of III-V semiconductors beyond InAs but also to three-dimensional substrates whose surfaces are converted into Zintl thin films, as well as to nanowires. We report the growth of two new compounds: Eu$_5$Ga$_2$As$_6$ thin films converted from GaAs substrates, and Eu$_5$Al$_2$As$_6$ thin films from AlAs films. We also convert GaAs nanowires of both wurtzite and zincblende structures into Eu$_5$Ga$_2$As$_6$ nanowires. Though the stoichiometry is the same as in the previously reported Eu$_5$In$_2$As$_6$ case, microscopy and diffraction reveal a single-phase Pnma symmetry group rather than Pbam, highlighting symmetry-guided topotactic pathways to new Zintl frameworks. The compounds host an intricate magnetic phase diagram with three magnetic transitions, including two distinct antiferromagnetic orders and a canted antiferromagnetic phase that evolves into another antiferromagnetic phase under applied field through a spin-flop transition. Ab initio calculations predict that both Zintls are semiconductors with gaps of 0.79 eV in Eu$_5$Ga$_2$As$_6$ and 0.90 eV in Eu$_5$Al$_2$As$_6$. The lower symmetry and increased structural complexity suggest suppressed lattice thermal conductivity, pointing to thermoelectric potential alongside prospects in spintronics and detector technologies. These results give an epitaxy-compatible route for discovering and integrating magnetic Zintl thin films and nanowires directly from relevant III-V semiconductors.
Comments47 pages, 20 figures, 2 tables
