A Microelectrothermal Bridge Circuit With Complementary Parameter Estimation Algorithm for Direct Measurement of Thermal Conductivity

We describe a novel microelectrothermal test structure and a complementary data analysis algorithm for direct measurement of the thermal conductivity of metallic thin films and nanowires. The device is a thermal analog of an electrical bridge circuit, such as the Wheatstone bridge, as is commonly used to measure electrical impedance. The microelectrothermal bridge circuit addresses the problem of parasitic heat loss to supporting structures-a major obstacle to direct measurement of thermal properties. A nonlinear least-squares parameter extraction method developed specifically for the thermal bridge circuit further reduces the influence of unmodeled heat paths and accounts for complex sample geometry. Thus, accurate measurements may be made when fabrication of suspended structures is difficult or undesirable. The technique is demonstrated on arrays of aluminum nanowires on glass substrates, with excellent results. The Al nanowire experiments are also used to show the improved performance of the parameter extraction algorithm over a standard approach.