Raman Measurement of Heat Transfer in Suspended Individual Carbon Nanotube

The excellent thermal performance of carbon nanotube (CNT) has been noticed long ago and attracted much attention. In the experiments, the electrical and thermal contact resistances remain the unsolved key problems causing undesirable measurement uncertainty. Recently, a micro-Raman spectroscopy technique has been applied to perform non-contact measurement for individual CNT, thus the contact resistances during the measurement process can be avoided. In this method, the temperature rise of CNT is a function of laser absorption probability and thermal properties, these parameters are coupled together. In this work, the thermal conductivity and optical absorption of the same CNT sample are decoupled and determined simultaneously. The thermal conductivity is obtained by measuring the temperature rise caused by a direct current heating, where the laser heating effect can be eliminated. Then the optical absorption is obtained by solving the heat transfer equation considering the thermal conductivity as a known parameter. The CNT sample is 24.8 mu m in length and 3 nm in diameter. The measured thermal conductivity is 2630 Wm(-1)K(-1) and the optical absorption is 0.194%. The heat transfer coefficient is evaluated using a kinetic two-layer model, which has been proven by the previous experiment. Because the length of CNT is much larger than the size of the focused laser spot, the experimental result is insensitive to the contact resistances at the ends of CNT.