通过激光诱导缺陷降低金属-石墨烯接触电阻
Reducing the metal-graphene contact resistance through laser-induced defects
AI总结：
本研究提出一种可规模化的激光辐照方法，通过在镍接触石墨烯器件的接触区诱导缺陷来降低比接触电阻，20mW激光可将R_C从900Ω·μm降至250Ω·μm，为石墨烯及二维材料的接触电阻优化提供了可行方案。
摘要：
石墨烯已被广泛研究用于各类电子和光电子应用。已报道的金属与石墨烯之间的接触电阻，更确切地说是其比接触电阻（R_C），范围从几十Ω·μm到几kΩ·μm不等。用于制备石墨烯欧姆接触的可量产解决方案仍是研究热点。在此，我们报道了一种基于石墨烯激光辐照的可规模化方法，用于降低镍接触器件中的R_C。采用波长λ=532 nm的激光在接触区域诱导缺陷，该过程通过显微拉曼光谱进行原位监测。物理损伤则通过异位原子力显微镜和扫描电子显微镜进行观测。我们采用传输线法（TLM），在环境和真空条件下，分别从经过激光处理和未经过激光处理的背栅石墨烯器件中提取R_C。结果显示，接触区经过激光辐照的器件R_C显著降低，且降低幅度与激光功率呈正相关。在20 mW激光功率辐照的器件中，获得了约250 Ω·μm的最低R_C，而未处理器件的R_C为900 Ω·μm。这种降低归因于缺陷密度的增加，缺陷会形成微晶边缘和面内悬挂键，从而增强载流子从金属向石墨烯的注入。我们的研究表明，激光辐照是一种可规模化的技术，可用于降低石墨烯以及潜在其他二维材料的R_C。
英文摘要：
Graphene has been extensively studied for a variety of electronic and optoelectronic applications. The reported contact resistance between metal and graphene, or rather its specific contact resistance (R{_C}), ranges from a few tens of Ω μm up to a few kΩ μm. Manufacturable solutions for defining ohmic contacts to graphene remain a subject of research. Here, we report a scalable method based on laser irradiation of graphene to reduce the R{_C} in nickel-contacted devices. A laser with a wavelength of λ = 532 nm is used to induce defects at the contact regions, which are monitored \textit{in-situ} using micro-Raman spectroscopy. Physical damage is observed using \textit{ex-situ} atomic force and scanning electron microscopy. The transfer line method (TLM) is used to extract R{_C} from back-gated graphene devices with and without laser treatment under ambient and vacuum conditions. A significant reduction in R{_C} is observed in devices where the contacts are laser irradiated, which scales with the laser power. The lowest R{_C} of about 250 Ω μm is obtained for the devices irradiated with a laser power of 20 mW, compared to 900 Ω μm for the untreated devices. The reduction is attributed to an increase in defect density, which leads to the formation of crystallite edges and in-plane dangling bonds that enhance the injection of charge carriers from the metal into the graphene. Our work suggests laser irradiation as a scalable technology for R{_C} reduction in graphene and potentially other two-dimensional materials.
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