Micro-discharge and electric breakdown in a micro-gap

Very weak light emission due to micro-discharges in the micro-gap of an electrostatic actuator under a high electric field can be imaged using a highly sensitive CCD camera. In this paper, we focus, in particular, on the relation between the micro-discharge and the electric field breakdown. Micro-discharges attributed to local breakdown is observed even if the electric field strength is below the breakdown threshold. The observations of the micro-discharge give important information on the irregularity and inhomogeneity of the electric field. It is found that irregular instability and inhomogeneous distribution of the electric field develop micro-discharges. The micro-discharge evaporates the electrode material, which results in increasing pressure in the gap, and finally grows to the breakdown. This effect seems to be remarkable, especially in narrow gaps. Furthermore, the electric breakdown threshold depends on the electrode material. A silicon-to-silicon gap configuration shows a higher breakdown threshold as well as the prebreakdown threshold in comparison to a silicon-to-metal gap.