Engineering thermal boundary conductance of a metal/polymer interface

Printable, flexible organic electronics is based on polymers and other organic molecules, and have the advantages of reducing dependence on silicon and rare earth materials, in addition to being light and low cost. Heat management of organic electronics is a challenge due to the large density of interfaces between highly dissimilar materials, such as metals and polymers. Heat conduction in low dimensional materials is currently one of the unsolved fundamental scientific issues, especially in the case of an interface with characteristic length scales ranging from a few atoms to tens of nanometers between dissimilar materials. Here we used spin-coating to fabricate 1-15 nm thick polymer (polymethyl methacrylate, PMMA) films on silicon substrate and coated with ultra-thin gold film or gold film with a 2 nm titanium layer interfacing the polymer. We employed frequency-domain thermoreflectance (FDTR) to measure the effective thermal conductivity of the polymer films and hence obtained the thermal boundary conductance between metal and polymer. The PMMA thickness dependent thermal boundary conductance was revealed. The presence of titanium layer increased thermal boundary conductance to twofold, and attributed to the strengthened mechanical adhesion between titanium and polymer compared to the gold-polymer interface. These results help inform the engineering of metal/polymer interfaces for maximizing heat transfer.