Thermal contact conductance of adhered microcantilevers

The thermal contact conductance G for polycrystalline silicon cantilever beams that are adhered to an underlying substrate is examined using two different optical techniques. Using time-domain thermoreflectance, we measure G=9±2 MW m−2 K−1 at 25 °C and G=4±1 MW m−2 K−1 at 150 °C. The room temperature value is confirmed using a modified Angstrom method, which establishes a lower limit of G>5 MW m−2 K−1. This contact conductance is a factor of 10–105 greater than values reported for metal–metal and ceramic–ceramic interfaces. The large interfacial conductance is consistent with the presence of a thin layer of water trapped between the cantilever and the substrate. The thermal conductivity Λ of the phosphorus doped polysilicon cantilever is nearly isotropic with Λcross plane=65 W m−1 K−1, and Λin plane=70 W m−1 K−1 at room temperature.