碳化硅材料中缺陷诱导铁磁性的研究

Defect-induced ferromagnetism, also referred as “d0 ferromagnetism” in contrast to traditional ferromagnets containing partially filled 3d or 4f electrons, not only challenges the basic understanding of ferromagnetism, but also allows for potential spintronic applications. Very recently, SiC single crystals have been shown to be ferromagnetic after ion and neutron bombardment or after Aluminum doping. As an important technologic material, SiC is commercially available at large scale and with high quality at the microelectronic grade. Therefore, SiC presents a suitable model system for studying defect-induced ferromagnetism in addition to carbon based materials. Tentatively, it is proposed that VSi-VC divacancies form local magnetic moments arising from sp states which couple ferromagnetically due to the extended tails of the defect wave functions. In this work, based on our previous research experience on magnetic semiconductors and ion beam material modification, we introduce the method of ion irradiation to the investigation of defect induced ferromagnetism. Non-magnetic ions of different energies will be selected for irradiation, such as H,O,N,Al, to probe into how (1) the surrounding of ferromagnetic defects and (2) carrier influences ferromagnetism. The possibility of SiC-based diluted magnetic semiconductors will also be inspected. Our project provides not only an alternative way to work out the mechanism of defect induced ferromagnetism, but also great perspective to realize SiC-based spintronics with room-termperature ferromagnetism.

缺陷诱导的铁磁性,不仅挑战了人们对传统铁磁性的认识，而且表现出良好的自旋电子学应用前景。做为一种典型的宽禁带半导体，SiC具有高热传导性和化学稳定性，同时可以较容易做到高质量的制备，因此是一种研究缺陷诱导铁磁性的可靠材料。最近的研究表明，SiC单晶在经历中子、惰性气体离子轰击或Al掺杂后表现出室温铁磁性。前期的工作确定了该铁磁性来自VSi-VC双空位。在该项目中，我们将成熟的离子束辐照技术应用于缺陷诱导铁磁性这一新兴的研究领域，提出采用不同能量的非磁性离子如H、O、N、Al对6H-SiC进行辐照，并结合高温退火处理来研究：1）周围化学环境对铁磁性的影响；2）不同载流子环境下铁磁性的变化以及载流子和局域磁矩间的耦合。本项目不仅推动对缺陷相关磁矩之间耦合机制的理解以及相关理论模型的建立，同时也为自旋电子学的发展提供一条新的思路。

SiC中缺陷诱导的铁磁性来源被证实来自VSi-VC双空位。在该项目中，我们在前期工作的基础上，1）采用不同能量的非磁性离子如H、O等对SiC单晶进行辐照，选取不同能量，不同剂量的离子产生不同的缺陷分布区域以及不同的化学环境，系统研究样品铁磁性的变化；2）采用磁性离子Mn注入结合不同高温退火条件，研究了载流子浓度等对铁磁性变化的影响。我们发现了磁矩周围化学环境、铁磁性离子替位掺杂等对铁磁性具有明显的作用。我们的研究结果不仅提供了缺陷相关铁磁性磁矩之间耦合机制的理解思路，同时也具有巨大的自旋电子学器件的应用前景。此外，在此基础上，我们还探讨了Si基稀磁半导体制备的可能性，成功实现了单晶Si中P型载流子的激活，通过优化条件，使得载流子浓度达到了成熟稀磁半导体的水平；以及实现了离子辐照精确调控GaMnAs材料的居里温度，并讨论了其费米能级附近的能带结构。

内容获取失败，请点击重试