Interfacial thermal conductance limit and thermal rectification across vertical carbon nanotube/graphene nanoribbon-silicon interfaces

Various models were previously used to predict interfacial thermal conductance of vertical carbon nanotube (CNT)-silicon interfaces, but the predicted values were several orders of magnitude off the experimental data. In this work, we show that the CNT filling fraction (the ratio of contact area to the surface area of the substrate) is the key to remedy this discrepancy. Using molecular dynamics, we have identified an upper limit of thermal interface conductance for C-Si interface which is around 1.25GW/m(2)K, corresponding to a 100% filling fraction of carbon nanotube or graphene nanoribbon on substrate. By extrapolating to low filling fraction (similar to 1%) that was measured in experiments, our predicted interfacial thermal conductance agrees with experimental data for vertical CNT arrays grown on silicon substrate (similar to 3MW/m(2) K). Meanwhile, thermal rectification of more than 20% has been found at these C-Si interfaces. We observed that this is strongly dependent on the interfacial temperature drop than the filling fraction. This new effect needs to be considered in future thermal interface materials design. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4790367