Irregular dielectric boundaries

In 1987, Swartz [73] measured the thermal boundary resistance between metal films and the dielectric substrates onto which the films were deposited, in the range 0.6-200 K. A typical example is the measurement of the thermal contact resistance between indium and sapphire [72]. To minimize the dependence on surface irregularities, indium was vacuum deposited onto the sapphire rods the two surfaces were then pressed together and annealed. Analogous measurements have been carried out also with lead and aluminium. In all these cases, it has been clear that the contact resistance was strongly dependent on the sample preparation. In particular, obtained data suggest that the contact between the two materials was not complete. 

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