Khosravi Rad Babak, Mehrfar Amir Hossein, Sadeghi Neisiani Zahra, Khaje Mahdi, Eslami Majd Abdollah
Optoelectronics and Nanophotonics Research Group, Faculty of Electrical and Computer Engineering, Tarbiat Modares University, Tehran, Iran.
Faculty of Electrical and Computer Engineering, Malek Ashtar University of Technology, Tehran, Iran.
Sci Rep. 2024 Apr 22;14(1):9190. doi: 10.1038/s41598-024-58360-9.
Contact resistance, as one of the main parameters that limits the performance of graphene-based transistors, is highly dependent on the metal-graphene contact fabrication processes. These processes are investigated and the corresponding resistances are measured based on the transfer length method (TLM). In fabrication processes, when annealing is done on chemical vapor deposition (CVD)-grown graphene samples that are transferred onto SiO/Si substrates, the adhesion of graphene to the substrate is improved, and poly methyl methacrylate (PMMA) residues are also reduced. When the metal deposition layer is first applied to the graphene, and then, the photolithography process is performed to define the electrodes and graphene sheet, the graphene-metal contact resistance is better than that in other methods due to the removal of photoresist residues. In fact, by changing the sequence of the fabrication process steps, the direct contact between photoresist and graphene surface can be prevented. Thus, the contact resistance is reduced and conductivity increases, and in this way, the performance of graphene transistor improves. The results show that the fabrication process has a noticeable effect on the transistor properties such as contact resistance, channel sheet resistance, and conductivity. Here, by using the annealing process and changing the order of photolithography processes, a contact resistance of 470 Ω μm is obtained for Ni-graphene contact, which is relatively favorable.
接触电阻作为限制基于石墨烯的晶体管性能的主要参数之一，高度依赖于金属 - 石墨烯接触制备工艺。基于转移长度法（TLM）对这些工艺进行了研究并测量了相应的电阻。在制备工艺中，当对转移到SiO/Si衬底上的化学气相沉积（CVD）生长的石墨烯样品进行退火时，石墨烯与衬底的附着力得到改善，聚甲基丙烯酸甲酯（PMMA）残留也会减少。当首先在石墨烯上施加金属沉积层，然后进行光刻工艺以定义电极和石墨烯片时，由于光刻胶残留的去除，石墨烯 - 金属接触电阻比其他方法更好。实际上，通过改变制备工艺步骤的顺序，可以防止光刻胶与石墨烯表面直接接触。因此，接触电阻降低且电导率增加，从而石墨烯晶体管的性能得到改善。结果表明，制备工艺对诸如接触电阻、沟道薄层电阻和电导率等晶体管特性有显著影响。在此，通过使用退火工艺并改变光刻工艺的顺序，对于镍 - 石墨烯接触获得了470Ω·μm的接触电阻，这是相对良好的。
