Thermal boundary conductance between carbon nanotubes and surrounding material by molecular dynamics simulations

The scaling down of feature size in electronics and nanodevices leads to increased concentration of heat. Management of the heat dissipation is currently the biggest limitation in building smaller and faster processors. Being motivated by a new use for carbon nanotubes as heat fins to cool nanosystems, this thesis aims to investigate the thermal boundary conductance between nanotubes and the surrounding materials, which is not well understood to this date. Characterization of the thermal boundary conductance is important also for electric devices in general as it determines the affordable electric load. The heat transport from a single-walled carbon nanotube (SWNT) to a matrix of surrounding liquid or solid argon (Ar), is simulated by molecular dynamics simulations. The entire SWNT was subjected to a pulse of heat to observe the interfacial heat transfer. Depending on the phase of the Ar, the key physics of the heat transfer at the interface are expected to range from random molecular collisions to modal energy transport based on the lattice vibrations (phonons). As a result, significant modal interactions were observed not only for solid but also for liquid Ar, since the liquid forms an adsorption layer around the SWNT with solid-like characteristics. The layer interacts strongly with the nanotube and suppresses vibrations (phonons) with a certain frequency band. Despite the considerable modal interaction, previously reported nanotube-length dependence of thermal conductance was not observed in the current simulations. The cause of the discrepancy is discussed by highlighting the difference of the two numerical studies. In conclusion, the thesis work characterized a key system for constructing thermal fins for the feature use in nanotechnology. The strong modal interaction observed between carbon nanotubes and the surrounding liquid Ar stimulates the idea to create thermal filters where a selected frequency bands can be assigned as the heat transfer channels between a carbon nanotube and the surrounding liquid.