Abstract：
Layered or chain materials have received significant research attention owing to their interesting physical properties, which can dramatically change when the material is thinned from bulk (three-dimensional) to thin two-dimensional sheet or one-dimensional (1D) chain form. Materials with the stoichiometry AX2 with A = Si or Ge and X = S or Se form an especially intriguing semiconducting class. For example, bulk silicon dichalcogenides (SiX2) consist of 1D chains held together by van der Waals forces. Although this structural configuration has the potential to reveal interesting physical phenomena within the 1D limit, obtaining SiX2 single chains has been challenging. We here examine experimentally and theoretically SiX2 materials in the low chain number limit. Carbon nanotubes serve as growth templates and stabilize and protect the structures, and atomic-resolution scanning transmission electron microscopy directly identifies the atomic structure. Two distinct chain structures are observed for SiX2. SixGe1-xS2(1-y)Se2y quaternary alloy chains are also synthesized and characterized, demonstrating tunable semiconducting properties at the atomic-chain level. Density functional theory calculations reveal that the band gap of these alloy chains can be widely tuned through composition engineering. This work offers the possibilities for synthesizing and controlling semiconductor compositions at the single-chain limit to tailor material properties.
摘要：
层状或链状材料由于其有趣的物理性质而受到了重要的研究关注，当材料从块状（三维）变薄到薄的二维薄片或一维（1D）链形式时，这可能会发生巨大变化。具有A=Si或Ge和X=S或Se的化学计量AX2的材料形成特别吸引人的半导体类。例如,块状硅二硫族化合物（SiX2）由范德华力保持在一起的1D链组成。尽管这种结构配置有可能在一维极限内揭示有趣的物理现象，获得SiX2单链一直是具有挑战性的。我们在这里通过实验和理论检查低链数极限的SiX2材料。碳纳米管作为生长模板，稳定和保护结构，和原子分辨率扫描透射电子显微镜直接识别原子结构。对于SiX2观察到两种不同的链结构。还合成了SixGe1-xS2（1-y）Se2y四元合金链并对其进行了表征，展示了在原子链水平上可调的半导体特性。密度泛函理论计算表明，这些合金链的带隙可以通过成分工程进行广泛的调整。这项工作提供了在单链极限下合成和控制半导体成分以定制材料特性的可能性。
