高性能石墨烯/二硫化钼接触特性及机理研究

In recent years, two-dimensional materials such as graphene and MoS2, with their devices, have become the new hotpot in semiconductor research. However, the performance of MoS2/based transistors is often limited by the large electrical resistance across the metal/MoS2 contact. This project aimed a hotspot and difficulty in the study on electrical contacts of semiconductor device, combining the metallic graphene with wide bandgap MoS2, nearly barrier-free ohm contacts to MoS2 transistors is achieved. Through a process of alloy-metal catalyzed, multiple porous structures with end-contacted edges are created in the graphene portions. We demonstrate that through a proper understanding and design of nanostructures of graphene and the right choice of number of MoS2 layers, the origin intrinsic interface scattering and band engineering of this 2D material can be harvested. This breakthrough is largely attributed to the fact that we succeeded in eliminating contact resistance effects that limited the device performance in the past unrecognized. As a theoretical investigation, based on thermal electrons emitting and density functional theory, the ohm contact interface state, coulomb scattering and the origin of the Schottky barrier height is discussed. This work will open up the way to further improvements in 2D semiconductor performance and introduces MoS2 as an interesting system for studying correlation effects in mesoscopic systems. It will hold great promise to meet the contact performance required for the integration of two-dimensional materials in future integrated circuits and flexible electron device.

近年来，以石墨烯、二硫化钼为代表的二维材料与器件成为国际半导体的研究热点。其中二硫化钼/金属界面的接触电阻问题已经严重阻碍了晶体管的性能。本项目针对国际二维材料在半导体器件接触电极研究中的热点和难点，将石墨烯零带隙金属性与二硫化钼宽带隙的半导体性相结合，利用多孔纳米结构的构筑剪裁，得到接近零势垒的欧姆接触，并建立完善的接触电极电荷输运模型。重点研究基于合金选择性刻蚀的机理，通过多孔结构的构筑和外延生长技术的结合，制备末端相连的有序石墨烯边缘以增强与二硫化钼、金属间界面接触。通过石墨烯纳米结构的剪裁、能带调控，探究二硫化钼层数、界面散射之间的关联机制，为接触电极的应用提供理论和实验基础。这项工作将利于丰富纳米结构技术和二维材料电子输运理论体系，并在介观体系中观察二硫化钼的关联机制开辟新道路。对于的加快二维材料在集成电路及柔性电子器件领域实用化进程，具有非常重要的科学意义及应用价值。

本项目针对二维材料在半导体器件接触电极研究中的热点和难点，将石墨烯零带隙金属性与二硫化钼宽带隙的半导体性相结合，利用多孔纳米结构的构筑剪裁，得到接近优良的欧姆接触，并建立完善的接触电极电荷输运模型。本项目进展顺利，在CVD法制备单晶石墨烯方面取得了突破性进步晶圆面积从2英寸到2米，而单晶晶畴尺寸从最初的数十微米，到超过一毫米，也给石墨烯器件制备提供坚实基础；首次采用低气压化学气相沉积技术一步法直接新型多孔雪花状石墨烯基纳米结构，该结构具有良好的电学性能，为新型电极接触提供基础；研究了不同氧等离子体处理时间下不同层状石墨烯膜与Ti/Au电极的二硫化钼膜的接触电阻，获得了低的接触电阻。基于石墨烯/二硫化钼范德华 外延异质结，利用多孔纳米结构的调控使得接触势垒低，从而得到低接触电阻、高迁移率的晶体管特性。通过石墨烯纳米结构的剪裁、能带调控，揭示了二硫化钼层数、界面散射之间的关联机制，为接触电极的应用提供理论和实验基础。在本项目的资助下，项目负责人以第一作者及通讯作者发表SCI论文7篇，申请及授权国家发明专利共11项，其中成果转化2项，顺利完成既定目标。