In-situ investigation on the microscale breakdown in air atmosphere by an optical diagnosis method

Electrical breakdown properties at microscale is very vital not only to the insulation issues of microdevices but also to the micro plasma applications. Herein, we reported an optical diagnosis method for the in-situ investigation on the microscale breakdown in air atmosphere. The in-situ optical measurement system comprises of the optical microscope to amplify the light emission (with the resolution of 1μm) and the Intensified charge-coupled device (ICCD) camera to capture the transient light emission (with the resolution of 2ns). Results show that when the gap width is 40 μm, the breakdown starts from the cathode for the flat-top breakdown, while the breakdown starts from the cathode and the anode simultaneously for the rising-edge breakdown. Moreover, the intensity of light emission around the electrodes is much higher than that inside the gap, indicating that the charged particles multiplication process mainly takes place close to the electrodes as the gap width decreases. The present study is envisaged to be important for the understanding of the initiation and propagation of charged particles under the pulsed voltage.