Metal-based piezoresistive sensing devices could find a much wider applicability if their sensitivity to mechanical strain could be substantially improved. Here, we report a simple method to enhance the strain sensitivity of metal films by over two orders of magnitude and demonstrate it on specially designed microcantilevers. By locally inhomogenizing thin gold films using controlled electromigration, we have achieved a logarithmic divergence in the strain sensitivity with progressive microstructural modification. The enhancement in strain sensitivity could be explained using non-universal tunneling-percolation transport. We find that the Johnson noise limited signal-to-noise ratio is an order of magnitude better than silicon piezoresistors. This method creates a robust platform for engineering low resistance, high gauge factor metallic piezoresistors that may have profound impact on micro and nanoscale self-sensing technology.

No abstract

No abstract

Abstract-Electromigration has long been studied in the context of interconnect reliability in integrated circuits. It has also been used to create metal electrodes with nanogaps for molecular electronics. Here we report a new application of electromigration as a tool for locally engineering the microstructure of thin metal films. By controlling the level of disorder in the system, electromigration enables us to modify the electrical and electromechanical properties of the film. We have developed and implemented a feedback control algorithm for high precision control of the electromigration process. We have demonstrated the usefulness of the technique by using it to enhance the strain sensitivity of a metal based piezoresistive transducer. This enhancement can be attributed to the change in microstructure of the film which in turn changes the electronic transport mechanism.