Transient thermoreflectance from graphene composites with matrix of indium and copper

Transient thermoreflectance was measured from In and In-graphene composite films pressed on to different substrates that include Si, GaAs, Cu and Cu-graphene composite. Measurements were also made from Al film deposited on substrates of Cu and Cu-graphene composite. The experimental results were modeled using solution to the thermal diffusion equation to determine the thermal conductivity of the phases and thermal conductance of the interface. The In-graphene and Cu-graphene composites are found to spread the heat more rapidly than In and Cu, respectively. The interface thermal conductance of In or In-graphene film pressed on to Cu was found to be smaller than the observed values for metal-metal contacts reported in the literature although higher than the value observed for the interface between Pb-Sn eutectic solder alloy bonded to Cu. The interface thermal conductance between Al film deposited on mechanically polished Cu or Cu-graphene composite is also found to be much lower than the value observed previously. The smaller value of interface thermal conductance of either In or In-gr or Al film on different substrates is explained by absence of atomic level bonding, presence of rough surfaces with incomplete contact and oxygen or water vapor at the interface. Copyright 2013 Author(s). This article is distributed under a Creative Commons Attribution 3.0 Unported License. [http://dx.doi.org/10.1063/1.4794801]