A Study of the Electrical Properties of the Polydopamine Coating of CNTs: A New Path to Fabricate Copper-Carbon Composites

Abstract

In present days, the continuous miniaturization of electronic devices comes along with a problematic reduction of their life-time. This is due to the underlying current density being operated increasingly close to the maximum current-carrying capacity (ampacity) of the materials (copper, gold...) used in the conduction channels of micro-circuitry. In this respect, there is a growing attention for new materials with higher ampacity and copper-carbon nanotube (CNT) composites could constitute a promising alternative. The interest of such copper-carbon composites relies on the combination of the complementary properties of both materials: the high conductivity of copper and the high ampacity of CNTs.However, the fabrication of an efficient Cu-CNT composite still remains a huge challenge and, up to now, the metal filling of a CNT matrix using electrochemical methods systematically requires an organic solvent based solution, which is not industrially and ecologically friendly. This constitutes an important drawback of those types of fabrication paths.A new promising way to fabricate such a composite by electrochemistry is shown in our work (see figure 1). It is based on the coating of CNTs by polydopamine (pda) cross-linked with copper ions. The coated CNTs are sprayed to form a matrix and the interstices are then filled with metallic copper by using an electrochemical step in aqueous solution.It is relevant to study how pda impacts the CNT surface conductivity and to try to increase it in order to promote electron transfer through the copper-CNT interface. In this respect, we want to evaluate the conductivity of CNT surface by using AFM probing. To assess the impact of pda, we compare conductivity values of uncoated CNTs with coated CNTs. We also show the change in conductivity when the coated CNTs are annealed at different temperatures under inert atmosphere conditions. To better understand the electrical properties, we characterize the CNT coatings before and after thermal treatment with FTIR, STEM, XPS, and DSC, which in particular shows the transformation of the pda layer and the formation of well-dispersed nuclei on the CNT surface. Figure 1