Metal nanofibrils embedded in long free-standing carbon nanotube fibers with a high critical current density

Abstract

With the growth of nanoelectronics, the importance of thermal management in device packaging and the improvement of high-current-carrying interconnects/wires for avoiding the premature failure of devices have been emphasized. The heat and electrical transport properties of the bulk may not be valid in the characterization of a material at the nanometer level, because the phenomena that occur at the interfaces and grain boundaries become dominant. The failure mechanism of bulk metal interconnects has been understood in the context of electromigration; however, in nanoscale materials, the effect of the heat dissipation that occurs at the nanointerfaces may play an important role. Here, we report the preparation of continuous carbon nanotube (CNT)–Cu composite fibers that possess Cu nanofibrillar structures with a high current-carrying capacity. Various-shaped CNT–Cu microfibers with different Cu grain morphologies were produced via Cu electroplating on continuous CNT fibers. Cu fibril structures were embedded in the voids inside the CNT fiber during the early stage of electrodeposition. The temperature-dependent and magnetic field-dependent electrical properties and the ampacity of the produced CNT–Cu microfibers were measured, and the failure mechanism of the fiber was discussed. The interconnection of Cu nanograins on the surface of the individual CNTs contributed to the enhancement in the charge-carrying ability of the fiber. The effective ampacity of the Cu nanofibrils was estimated to be ~1 × 107 A/cm2, which is approximately 50 times larger than the ampacity measured for a bulk Cu microwire.