Effects of Ti-based interposer layer on graphene/carbon nanotube nano-contact resistance

Abstract

We demonstrate that the carbon nanotube (CNT)-graphene contact resistance can be improved by the introduction of an interposer layer and its surface treatment in order to improve the interfacing between vertical CNT interconnects and horizontal graphene lines. To this end, a method to measure the rear-end contact resistance over a nano-sized area without the need for a separate test structure was developed. Graphene-CNT exhibits a high contact resistance of 11. 66 MΩ/nm2 due to weak van der Waals force coupling. This contact resistance can be reduced via addition of a contact layer composed of Ti (resistance of ~1.23 MΩ/nm2) or Cu (~1.65 MΩ/nm2) between graphene and the CNT. In particular, the contact resistance between the vertical CNT interconnect and the horizontal graphene line is greatly improved when a Ti interlayer is applied because Ti exhibits excellent wettability with carbon, which leads to strong TiC bonding that affords a Schottky-barrier-free ohmic contact. Furthermore, the contact resistance can be improved by removing TiO bonds through a surface treatment.