Electric field breakdown at micrometreseparations in air and nitrogen atatmospheric pressure

For efficient operation, micromotors and microactuators, such as those employed in microsystems, are required to operate with high electric fields at electrode separations of the order of micrometres. An apparatus was built to accurately measure the breakdown voltage for electrode spacings as low as 0.5 µm. Breakdown voltage measurements in air and nitrogen are presented and discussed for the gap range 0.5 to 15 µm. Energy dispersive analysis of X-rays (EDAX) confirms the transfer of material from cathode to anode and vice versa during the breakdown mechanism. The Paschen law has been confirmed not to be applicable at gap settings of less than 4 µm. The shape of the curve and the breakdown voltage values are found to be the same for different gases and different high pressures up to 4 µm separation. Below this value, an analytical explanation of the breakdown voltage based on quantum tunnelling of electrons is obtained in terms of electrical field enhancement at microprotrusions and the work function of the electrode material.