I-II-V族稀磁半导体的结构和物性关联机制研究

We focus on the synthesis, microstructural and physical property studies of the diluted magnetic I-II-V semiconductor Li(Zn, Mn)As series. Using aberration-corrected transmission electron microscopy and scanning transmission electron microscopy, we plan to carry out microstructural investigations with atomic resolution for the paramagnetic and ferromagnetic Li1+yZn1-xMnxAs (Nominal composition: 0 ≤ x ≤ 0.15; -0.1 ≤ y ≤ 0.2) compounds. We plan to determine the relationship between the structures and different Curie temperatures Tc and reveal the origin of modulated structures. In this project, we plan to conduct several works. 1) We will reveal the charge controlling mechanism induced by Li doping. 2) Besides, we will analyze the spin controlling mechanism induced by Mn doping and the long range ordering caused by the substitution of Zn by Mn. Based on the above studies, we aim to reveal the relationship between the structures and properties, and the charge and spin controlling mechanism in the diluted magnetic semiconductors. We will provide meaningful information for the searching for the diluted magnetic semiconductors with novel and excellent properties.

制备I-II-V族稀磁半导体Li(Zn, Mn)As系列样品，开展相应的电学性质和磁学性质的研究，利用球差校正透射电镜对顺磁和铁磁Li1+yZn1-xMnxAs样品（名义配比0 ≤ x ≤ 0.15；-0.1 ≤ y ≤ 0.2）进行原子尺度的微结构分析，确定对应不同居里温度TC的晶体结构，揭示形成调制结构的原因。研究Li掺杂的电荷调控机制，同时，探索Mn原子掺杂所构成的有序结构及其自旋调控机制。揭示I-II-V族稀磁半导体的微观结构与新颖物性的关联，探究电子电荷与自旋两个自由度调控的物理机制，为寻找性能优异的稀磁半导体材料提供实验依据。

采用固相反应方法分别合成了单相性好的Li(Zn, Mn)As及Li(Zn/Cd, Mn)P系列多晶样品。通过X射线衍射验证其单相性，并对这些样品进行了磁性和电输运性质的测量，确定了居里温度Tc和引入的载流子类型。通过球差校正电镜对调制相进行了微结构分析，研究了调制结构的起源和与物性的关联机制。构造了相应的结构模型，并对实验数据进行了模拟。在Li1.0Zn0.9Mn0.1As1.0顺磁样品和Li1.1Zn0.9Mn0.1As1.0铁磁样品（Tc ~ 37 K）中，通过HAADF和ABF像研究，首次发现Li和Zn离子位置的交换产生2a公度调制结构。根据第一性原理计算，推断过量的Li掺杂会在Li1+yZn0.9Mn0.1As1.0系列样品中引起铁磁性。此外，制备了Li(Cd, Mn)P系列样品，比制备的Li(Zn, Mn)P系列样品的Tc高三分之一。我们总结出：在以上I-II-V族稀磁半导体体系中，调制结构将影响由Li掺杂引起的电子电荷控制机制，而Mn掺杂所引起的电子自旋调控机制受到过量Li离子掺杂的影响；通过增加体系中p型载流子的浓度，可以有效提高居里温度。