Low-resistance electrical contact to carbon nanotubes with graphitic interfacial layer

Carbon nanotubes (CNTs) are promising candidates for transistors and interconnects for nanoelectronic circuits. Although CNTs intrinsically have excellent electrical conductivity, the large contact resistance at the interface between CNT and metal hinders its practical application. Here, we show that electrical contact to the CNT is substantially improved using a graphitic interfacial layer catalyzed by a Ni layer. The p-type semiconducting CNT with graphitic contact exhibits high on-state conductance at room temperature and a steep subthreshold swing in a back-gate configuration. We also show contact improvement to the semiconducting CNTs with different capping metals. To study the role of the graphitic interfacial layer in the contact stack, the capping metal and Ni catalyst were selectively removed and replaced with new metal pads deposited by evaporation and without further annealing. Good electrical contact to the semiconducting CNTs was still preserved after the new metal replacement, indicating that the contact improvement is attributed to the presence of the graphitic interfacial layer.