Nanometer gaps by feedback-controlled electromigration

Nanometer-sized gap (or nanogap) is one of the most fundamental devices in the nanotechnology field. Park et. al., first proposed the open-circuit electromigration method to fabricate nanogaps, but the process is only repeatable if Au film is thinner than 20 nm. To overcome these drawbacks, we develop the feedback-controlled electromigration process and find that not only repeatable nanogaps can be created in thicker film (up to 120 nm or thicker in our experiments), but superior gap size control and topology are obtained. Moreover, we develop two new approaches to make free-standing nanogaps. The tunneling current between the nanogap electrodes was used to demonstrate a sensitive pressure and/or temperature sensor. Finally, we also develop a simple thermal-expansion method to measure the gap size without needing delicate instrument.