Effect of underetching on thermal conductivity measurement of suspended nanofilm

The measurement of the in-plane thermal conductivity of a nanofilm by the direct-current heating method is examined by a numerical heat transfer simulation to obtain reliable data for nanosensor applications. A platinum film of 500 nm in width and 10 μm in length is fabricated to be suspended between two terminals. An underetched part always exists on the edge of the terminals owing to the isotropic etching process, which causes a temperature jump at the end of the suspended film. As a result, the thermal conductivity measured by the direct- current heating method is found to be underestimated from the intrinsic properties of the suspended nanofilm. Numerical simulations are conducted to calculate the temperature jump and the necessary correction of thermal conductivity is derived, which critically depends on the width of the underetched part. The corrected thermal conductivity is discussed with the simultaneously obtained electrical conductivity in comparison with the bulk data.