Co2MnSi/石墨烯异质结向Ge沟道高效低阻自旋注入及输运性质研究

Semiconductor-based spintronic device in which both the charge and spin of the electron are utilized to provide new functionalities such as nonvolatility，is one of the candidates for next generation electronic devices. A semiconducting germanium channel with high electron mobility is one candidate of the next generation MOSFETs, and thus studies on spintronic devices with a germanium channel have attracted increasing attention in recent years. However, the evolvement of the germanium spintronic device is seriously delayed at present due to the low spin injection efficiency, high resistance-area product, the unclear transport properties of electrons in germanium channel and the unknown physical mechanism of the anomalous scaling of Hanle effect curves. To solve the above-mentioned issues, we proposed a new research program here. Firstly, we will prepare a new heterostructure consisting of Co2MnSi/graphene/Ge, which will be further fabricated with three-terminal and four-terminal configurations to achieve an efficient and low-resistance spin injection into germanium. Secondly, the spin transport properties of the electrons in germanium channel will be disclosed by the measurement of a temperature and a bias voltage dependence of Hanle and spin valve effect. Finally, the spin injection method with three-terminal configuration and the x-ray photoelectron spectroscopy technology will be comprehensive utilized to analyze the physical mechanism of Hanle effect from electrics and energy band structures. The findings may open up a new way for future germanium-based spintronic devices and have great theoretical significance and valuable potential applications.

综合利用电子的电荷和自旋两种属性而发展的半导体自旋器件因具有信息存储的非挥发性等优点是最具前景的下一代电子器件之一。半导体Ge因具有高电子迁移率是下一代MOSFET的沟道材料之一，故Ge自旋器件备受关注。但目前向Ge沟道的自旋注入效率低、结电阻面积乘积高、自旋电子在Ge中的输运性质及影响Hanle曲线幅值的物理机制不清楚，使Ge自旋器件发展较为缓慢。针对此问题，本项目首先构筑新的Co2MnSi/石墨烯/Ge异质结，将其制备成三端子和非局域四端子电极配置的器件结构，拟实现向Ge沟道高效低阻自旋注入。其次，测定Hanle和自旋阀效应的温度和偏压依存性，拟揭示自旋电子在Ge沟道中的输运性质。最后，综合采用三端子电极配置的自旋电子注入方法和x-射线光电子能谱技术从电学和能带结构两方面研究影响Hanle曲线幅值的物理机制。以上研究成果可为Ge自旋电子器件开辟新途径，具有重要理论意义和应用前景。

本项目主要围绕从Co2MnSi/石墨烯异质结向Ge沟道高效低阻自旋注入及输运性质进行研究，旨在解决向Ge沟道的自旋注入效率低、结电阻面积乘积高、自旋电子在Ge中的输运性质及影响Hanle曲线幅值的物理机制不清楚等问题。根据项目申请书的研究内容，首先构筑了Co2MnSi/石墨烯/Ge异质结器件结构，通过x射线衍射谱图和VSM分别测定了异质结的晶体结构和磁学性质，实验结果表明，制备的异质结具有良好的晶体结构和磁学性质；其次，制备了三端子电极配置的器件结构，研究了石墨烯对Co2MnSi/石墨烯/Ge异质结肖特基势垒的影响，实验结果表明，石墨烯的厚度对Co2MnSi/石墨烯/Ge异质结的肖特基势垒有非常大的影响，Co2MnSi/石墨烯/Ge异质结的肖特基势垒高度由没有插入石墨烯时的0.61eV变成插入两层石墨烯后的0.34eV。经过对比分析，我们认为在插入石墨烯后，引起肖特基势垒高度降低的主要原因是金属诱导的带间电荷效应；最后制备了三端子电极配置的器件结构，测定了器件的Hanle效应，揭示了自旋电子在Ge沟道中的输运性质。在本项目的经费支持下，已在本领域主流期刊发表学术研究论文4篇，尚有后续结果待发表；在该项目实施过程中，共协助培养博士研究生2名，培养硕士研究生2名，参加国际及国内学术会议2次。总体而言，按计划开展了相应的研究工作，基本达到了预期目标要求。