Thin Film Diluted Magnetic Semiconductors with Tetradymite Structure

该项目探讨了同时存在的电子和自旋自由度的tetradymite型A2V B3VI（A = Bi，Sb; B = Te，Se）家庭的半导体。通过这些材料的薄膜，可以在四亚甲基石型半导体中引入相对高浓度的磁性杂质，从而获得更高的居里温度。该项目的重点是几个目标：1）展示Sb2Te3，Bi2Te3和Bi2Se3薄膜的生长，以及这些二元化合物掺杂过渡金属的合金和超晶格; 2）探索磁性杂质的掺入上限（相图）在这些主机;和3）追求一个全面的程序表征的结构，磁性，以及所获得的DMS（稀磁半导体）膜的输运性质。磁杂质的作用在辉碲铋矿半导体和它们的影响性能将研究采用电导率，磁阻，热电，热导率，比热，霍尔效应，磁化强度，和磁化率测量从2K到300K的温度和0至9 T的磁场。该项目有望推进稀磁半导体的基础知识，从而为未来的自旋电子学应用奠定基础。由于所提出的材料中使用的晶体结构和磁性离子与传统的稀磁半导体（如Mn掺杂的III-V族或II-VI族化合物）明显不同，因此该项目可能会对半导体磁性的基本问题以及可能的磁性问题产生新的影响。具有明显的八面体原子配位的碲铋矿型晶体结构的高度各向异性环境可能在磁序的发展中起关键作用;这与具有明显的四面体键合的Mn掺杂的锌尖晶石或纤锌矿结构的立方环境形成对比。该项目解决了材料科学与技术相关性主题领域的基本材料和凝聚态物理研究问题，并强调研究与教育的一体化。研究生和本科生将参与电子/磁性材料的合成，加工和表征。在MBE增长，半导体物理和磁学领域的研究生和本科生的培训为他们提供了研究和教育的特殊机会，以及对未来劳动力的良好投资。该项目由DMR电子材料和凝聚态物理计划共同支持。

This project explores the simultaneous presence of electronic and spin degrees of freedom in the tetradymite-type A2V B3VI (A=Bi, Sb; B=Te, Se) family of semiconductors. The incorporation of relatively high concentrations of magnetic impurities in tetradymite-type semiconductors, and thus higher Curie temperatures, is sought through thin films of these materials. The project focuses on several objectives: 1) to demonstrate the growth of thin films of Sb2Te3, Bi2Te3, and Bi2Se3 -as well as alloys and superlattices of these binary compounds-doped with transition metals; 2) to explore the upper limits of incorporation of the magnetic impurities (phase diagram) in these hosts; and 3) pursue a comprehensive program of characterization of the structural, magnetic, and transport properties of the obtained DMS (dilute magnetic semiconductor) films. The role of the magnetic impurities in the tetradymite semiconductors and their impact on properties will be studied employing electrical conductivity, magnetoresistance, thermopower, thermal conductivity, specific heat, Hall effect, magnetization, and magnetic susceptibility measurements from temperatures of 2K to 300K and in magnetic fields of 0 to 9 T. The project is expected to advance basic knowledge of diluted magnetic semiconductors and thereby help lay groundwork for future spintronics applications. Since the crystal structure and the magnetic ions utilized in the proposed materials are distinctly different from traditional diluted magnetic semiconductors such as Mn-doped III-V or II-VI compounds, the project may shed new light on fundamental issues of magnetism in semiconductors, and possibly of magnetism generally. The highly anisotropic environment of the tetradymite-type crystal structure with its pronounced octahedral coordination of atoms may play a key role in the development of magnetic order; this is in contrast to the cubic environment of Mn-doped zinc-blende or wurtzite structures with their distinct tetrahedral bonding.%%% This project addresses basic materials and condensed matter physics research issues in a topical area of materials science with technological relevance, and places emphasis on the integration of research and education. Graduate and undergraduate students will be involved in the synthesis, processing, and characterization of electronic/magnetic materials. Training of graduate and undergraduate students in the areas of MBE growth, semiconductor physics, and magnetism provides special opportunities for them in research and education, and a sound investment in the future workforce. The project is jointly supported by the DMR Electronic Materials and Condensed Matter Physics programs.***