A thermophone-based bridge circuit for the measurement of electrical and thermal properties of thin films

Abstract

Sound can be generated via modulated Joule heating of thin conductive films. Its amplitude and phase are sensitive to the electrical and thermal properties of the film. Here we show how such sound can be used to measure and quantify these properties. In particular, we experimentally determine the relative conductances of electrical paths in a multi-branched thin film, which can then be used to find the temperature dependence of the film conductance. This is achieved by nullifying the sound at a given point in the sound field using simple voltage control. This method, essentially an acoustic analogue of an electrical bridge circuit, is advantageous since it allows for electrical and thermal properties to be measured simultaneously. These attributes benefit the characterisation of complex circuit architectures, as well as thermal sensing.