近表面掺杂SnO2外延薄膜的磁性修饰及其对石墨烯的自旋注入研究

Spintronic materials and devices are striking subjects and have aroused considerable interest in both academic and industrial community in the past years, which have not only scientific significances but also wide application prospects. In this proposal, the magnetic behavior of near-surface doped epitaxial SnO2 films and its efficiency of spin-injections of graphene will be investigated. In the preresearch of this proposal, room-temperature ferromagnetism has been observed in epitaxial SnO2 films. The method of near-surface doping will improve the concentration of the substituted defects and reduce the interaction distance between local magnetic moments, thus, further enhance the long-range ferromagnetic exchange and spin polarization of the system; Using epitaxial SnO2 film as a tunnel barrier, it can be good candidate of spin-injections materials into graphene by doping with magnetism, which have well lattice and resistance compatibility. It will transport the spin-polarized currents into graphene efficiently; At last, we take these near-surface-doped epitaxial SnO2 films as the basic spin-injection materials to design graphene-based spin diode or field-effect transistor, realizing spin injection, transportation and detection in future devices.

自旋电子材料及其相关器件是近年来的研究热点，受到学术界和工业界广泛关注，该研究不仅具有重要的科学意义而且蕴含着广泛的应用前景。本项目提出研究近表面掺杂SnO2外延薄膜的磁性及其对石墨烯的自旋注入效率。前期工作已在体掺杂的SnO2外延薄膜中观察到室温铁磁性，本研究中通过近表面掺杂的方法提高替位缺陷的浓度并降低所诱发局域磁矩的相互作用距离，从而进一步增强该体系的长程铁磁交换作用及自旋极化率；直接选取SnO2外延薄膜作为隧穿层，通过对隧穿层的掺杂构造出与石墨烯具有良好晶格和阻抗匹配的自旋注入材料，将实现石墨烯中自旋极化电流的高效注入；最后，以自旋注入材料的研究作为基础设计石墨烯基自旋二极管或场效应管，对自旋流加以调控，实现从自旋注入、输运到探测的器件化预测。

自旋电子材料及其相关器件是近年来的研究热点，受到学术界和工业界广泛关注，且石墨烯等二维材料的发现为微型化电子器件提供了新的平台。因此，在低维材料中实现高自旋极化输运不仅具有重要的科学意义而且蕴含着广泛的应用前景。本项目提出研究近表面掺杂SnO2外延薄膜的磁性及其对石墨烯的自旋注入效率。前期工作已在体掺杂的SnO2外延薄膜中观察到室温铁磁性，本研究中通过近表面掺杂的方法提高替位缺陷的浓度并降低所诱发局域磁矩的相互作用距离，从而进一步增强该体系的长程铁磁交换作用及自旋极化率。发现Al掺杂SnO2样品中呈现稳定的室温铁磁性，然而磁矩大小远低于理论值。通过后续的氧化退火处理，发现体系的局域磁矩主要来自于Al替位缺陷附近的氧空位。直接选取SnO2外延薄膜作为隧穿层，通过对隧穿层的掺杂构造出与石墨烯具有良好晶格和阻抗匹配的自旋注入材料，并对其自旋输运行为进行分析。利用第一性原理计算方法，分析的实现石墨烯高自旋极化的理论机制，发现自旋极化材料与石墨烯界面的耦合作用对自旋注入效率至关重要。通过施加应力和背栅电压，可以加强界面耦合作用，从而对体系的自旋极化率进行调控。该研究为解明了诱发非磁性体系高自旋极化的主要机理，为石墨烯基自旋场效应管的实验设计提供理论支撑。