Department of Electrical and Computer Engineering, National University of Singapore , Singapore, Singapore 117583.
Nano Lett. 2014 Jul 9;14(7):3840-7. doi: 10.1021/nl500999r. Epub 2014 Jun 10.
Annealing is a postprocessing treatment commonly used to improve metal-graphene contacts with the assumption that resist residues sandwiched at the metal-graphene contacts are removed during annealing. Here, we examine this assumption by undertaking a systematic study to understand mechanisms that lead to the contact enhancement brought about by annealing. Using a soft shadow-mask, we fabricated residue-free metal-graphene contacts with the same dimensions as lithographically defined metal-graphene contacts on the same graphene flake. Both cases show comparable contact enhancement for nickel-graphene contacts after annealing treatment signifying that removal of resist residues is not the main factor for contact enhancement. It is found instead that carbon dissolves from graphene into the metal at chemisorbed Ni- and Co-graphene interfaces and leads to many end-contacts being formed between the metal and the dangling carbon bonds in the graphene, which contributes to much smaller contact resistance.
退火是一种常用的后处理方法，用于改善金属-石墨烯接触，其假设是在退火过程中去除夹在金属-石墨烯接触处的残留物质。在这里，我们通过进行系统研究来检验这一假设，以了解导致退火引起的接触增强的机制。我们使用软阴影掩模，在同一石墨烯薄片上与光刻定义的金属-石墨烯接触相同的尺寸制造了无残留的金属-石墨烯接触。在退火处理后，镍-石墨烯接触的两种情况都表现出相当的接触增强，这表明去除残留物质不是接触增强的主要因素。相反，发现碳原子从石墨烯中溶解到化学吸附的 Ni 和 Co-石墨烯界面中的金属中，导致金属和石墨烯中悬空的碳键之间形成许多端接触，这有助于减小接触电阻。
