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. Nanoscale metal fibrils increase the maximum current a spun carbon nanotube fiber can carry before failing, researchers in South Korea demonstrate. Ensuring that components don’t overheat is a crucial consideration when designing electronic devices. High electrical currents can heat and thus damage the wires, or interconnects, that link different parts of the circuit. This is particularly important in nanoelectronics, where the interconnects are narrow. Sang Hyun Lee from the Korea Institute of Science and Technology, Jeonbuk, and colleagues addressed this problem by embedding copper fibrils within continuous carbon nanotube fiber. They compared various fibril shapes to systematically study the electrical and thermal properties at the interface between the copper and the carbon nanotube. The maximum current their composite fibers could tolerate before damage occurred was fifty times higher than for conventional copper microwires. The copper nanofibrils are formed at the void inside the long continuous carbon nanotube (CNT) fiber by electroplating. Electrical conduction through the composite fiber was dominated by the nanofibrils even though their cross-sectional area is much smaller than that of CNTs. The nanofibrils could carry a very high current density due to their bamboo-like structure and the thermal dissipation through CNTs.