站立式石墨烯嵌层结构的强磁阻效应产生原理与调控研究

Magnetoresistance effect devices are widely applied in electric navigating and magnetic field measurement, consuming a lot of metal resources since they are prepared from magnetic metallic films. Since graphene can generate magnetoresistance effect due to spin polarize at the edge defects, it has attracted much attentions, though the directly growth of graphene based 3-dimensional magnetoresistance device is not realized yet. Based on above background, this application proposed a scientific problem of "Originating Principles and Managing Research of Strong Magnetoresistance Effect in Standing-Up Graphene Sheet Embedded Carbon Structure", and tend to carry out studies in three aspects: magnetoresistance originating due to orderly arrangement of embedded graphene sheets, the enhancement of magnetoresistance due to size effect, and the response of parallel connected graphene sheets. The graphene sheets are vertically formed by low energy electron inducing, the graphene sheets stacking, in plane size and parallel connected number are modified by electron irradiation parameters, growth height and mask size. ESR and Raman spectra are introduced to study the electronic structure, thereafter the originating principles of strong magnetoresistance are proposed. PPMS is introduced to investigate the magnetoresistance value, thereafter the managing principles of magnetoresistance is proposed. This research aims at revealing the originating of magnetoresistance in standing-up graphene sheet, and provide scientific foundamentals for the design of new graphene-based magnetoresistance devices.

磁阻效应传感器在现代微机电系统中发挥着重要作用。由于其消耗了大量金属资源，亟需研制新型非金属磁阻效应器件。多层石墨烯由于边缘与缺陷处自旋极化引起的磁阻效应而得到极大关注，但目前尚未实现磁阻效应器件的原位制造。针对上述背景，本研究提出"站立式石墨烯嵌层结构的强磁阻效应产生原理与调控研究"这一科学问题，围绕石墨烯嵌层有序排列的磁阻效应起源，尺寸效应下磁阻效应的增强机制和多嵌层并联下磁阻效应的协同响应等三项内容开展研究。以电子照射诱导碳原子键合实现石墨烯嵌层站立生长，通过照射电子密度与能量，生长高度和掩模间距对其生长形态、层内尺寸和并联嵌层数量进行原位调控。利用电子自旋共振和拉曼光谱分析电子结构，探讨磁阻效应产生原理，利用物理特性测试系统分析磁致电阻变化，探索磁阻效应增强机制与调控原理。本研究旨在揭示站立式石墨烯嵌层结构的强磁阻效应产生原理，为新型石墨烯基磁阻效应器件设计提供科学基础。

围绕“站立式石墨烯嵌层结构的强磁阻效应产生原理与调控研究”，重点开展工作内容如下：1.低能电子照射下站立式石墨烯嵌层结构的诱导生长与调控；2.站立式石墨烯嵌层结构的室温强磁性产生原理与调控；3.站立式石墨烯嵌层结构的强磁阻效应产生原理与调控；4.离子/电子混合照射纳米表面制造原理。采用ECR低能电子照射方式诱导石墨烯嵌层结构在衬底表面站立生长，得到了电子照射能量与密度对站立式石墨烯嵌层的结构与形态调控规律，获得了国际上最强的室温铁磁性碳纳米表面(0.37emu/g)，并首次提出了电子照射调控下石墨烯纳晶结构演化与电学磁学特性的相图(Wang, et. al., Nanoscale, 2015, 7:4475)；发现了站立式石墨烯嵌层结构的室温强磁阻效应，提出了基于石墨烯边缘铁磁性诱导的载流子自旋散射输运机制以及磁阻效应产生机理，并在国际上首次利用变温拉曼光谱捕捉到载流子密度突变导致的铁磁性-反铁磁转变(Wang, et. al., Carbon, 2017, 112:162-168)；利用电子照射对非晶碳纳米表面进行后处理，诱导其表面形成石墨烯纳晶结构，利用离子照射对石墨烯嵌层结构进行刻蚀，显著降低其表面粗糙度，获得超光滑导电碳纳米表面。在国际上首次提出离子/电子混合照射的纳米表面制造原理(Wang, et. al., Surf. Coat. Tech., 2016, 308:50-56)，以及基于电子照射诱导化学反应的超薄碳纳米表面刻蚀加工方法(Wang, et. al., Appl. Phys. Lett., 2016, 109:053104)。研究成果对深入理解站立式石墨烯嵌层结构的自旋输运特性有重要启示意义，为进一步探索碳基室温磁性纳米传感器打下了坚实基础，为拓展低能电子照射在先进纳米制造的应用开辟了新思路。