碳纳米管接触电阻的研究

Carbon nanotubes are attracting extensive research due to their excellent properties. High contact resistance is one barrier to their applications in many fields such as micro-electronics, sensors, and new energy. The contact mechanism of carbon nanotubes with metals has not been fully understood so far. Existing models of contact resistance are often based on bulk materials and inapplicable at the nanoscale. Techniques and methods for improving electrical contact are still needed from an application point of view. The proposal aims to a systematic study of contact resistance of carbon nanotubes and its influencing factors, the conditions and methods for achieving a low contact resistance. In particular, a model which is applicable to carbon nanomaterials such as carbon nanotubes will be established and doping and current flow for lowing contact resistance will be investigated. The combination of these techniques for lowing contact resistance with electrode gap impedance measurement and feedback control during dielectrophoresis will also be studied for realizing automatic assembly of carbon nanotubes with low contact resistance. The research helps promote the industrial application of carbon nanotubes, especially in the fields related to nanoelectronics. The results will provide guidance to the study of contact resistance of other advanced nanomaterials including graphene.

碳纳米管由于卓越的性能成为当前纳米技术领域研究的热门材料，但与金属之间过高的接触电阻阻碍了其在微电子、传感器、新能源等诸多领域的应用。目前，碳纳米管与金属界面接触电阻的形成机理尚不完全清楚，现有分析模型大都基于宏观的块体材料，不适合纳米尺度材料的研究；在应用方面，有效地改善碳纳米管接触电阻的技术和方法依然缺乏。此立项旨在系统研究影响碳纳米管接触电阻的各种因素，研究碳纳米管与金属界面实现低接触电阻的条件和方法，特别是研究适合于碳纳米管等纳米材料的接触电阻模型以及通过掺杂和通电产生焦耳热等技术有效降低碳纳米管接触电阻的方法，并研究将降低接触电阻方法与碳纳米管介电电泳组装间隙阻抗测量与反馈控制技术相结合，从而实现高自动化程度的碳纳米管低接触电阻组装。该研究对碳纳米管在纳米电子相关领域的应用将起到重要的推动作用，同时为其他先进纳米材料如石墨烯接触电阻的研究提供指导。

卓越的电学、热学和力学性能使碳纳米管和石墨烯成为当前纳米技术研究领域的热门材料，但与金属之间高的接触电阻阻碍了碳纳米管和石墨烯在纳米电子、新型传感器和新能源等众多领域的应用。本项目对碳纳米管的接触电阻进行了较为系统的理论与实验研究。首先，利用基于密度泛函理论的第一性原理构建了本征、含缺陷、掺杂碳纳米管和石墨烯与金属界面的纳米尺度接触模型，并对碳纳米管和石墨烯与金属之间的交互作用从吸附能、电荷转移、电荷密度、前线轨道、能带结构和态密度等几方面进行了模拟计算和分析，进而研究了碳纳米管和石墨烯的结构和尺寸、掺杂元素种类、掺杂点位、掺杂浓度、金属电极材料及接触方式对界面电子输运性能和接触电阻的影响。结果表明掺杂可有效改善碳纳米管和石墨烯与金属界面的交互作用和电子输运性能，进而改善碳纳米管和石墨烯与金属之间的接触电阻。其次，通过氢气热还原、无电沉积及以金属有机框架为媒介对碳纳米管的Au、Pd、Ni、Zn、Co等过渡金属掺杂进行了实验研究，探索出了使得掺杂金属纳米粒子粒径均一、分散均匀、掺杂量适中、与碳纳米管实现有效结合的工艺方法和参数。同时，研究了通电产生焦耳热过程中交变电压幅值、频率及通电时间对改善碳纳米管接触电阻的影响，得出电压是主要影响因素，施加幅值为1.5-3.5V之间的交变电压能够获得有效的降阻效果，电阻降低幅度最高可达50%。最后，采用间隙阻抗测量技术和程序控制对碳纳米管的介电电泳组装过程和随后的通电改善接触电阻过程进行实时监测和反馈控制，发掘出了一套既稳定可靠又具备较高自动化程度的碳纳米管组装-降阻技术。本项目研究对碳纳米管和石墨烯的应用将起到重要的推动作用，同时也为其他先进纳米材料接触电阻的研究提供指导。