Study Of The Breakdown Characteristics Of Micro-electrodes In Atmospheric Pressure By PIC/MCC Simulation

Micro-discharge is a discharge which is limited in a narrow space.It is different from the conventional discharge structure.For example,the breakdown characteristics will diverge from the Paschen curves in large-scale counterparts.At present,the micro-discharge is widely used in industrial fabrication,spectrum analysis,equipment testing and other fields.So the micro-discharge has drawn more attentions in plasma research.In order to understand the characteristics of micro-discharge,the discharges between micro-electrodes at atmosphere pressure were investigated by PIC/MCC method,and the influences of dielectric layer surround the discharge space were also analyzed.Firstly,the breakdown characteristics in a small space defined by micro-electrode at atmosphere pressure were investigated.The distribution of electrons,electron energy,and the accumulation of charge on the dielectric surface were analyzed.It shows that the breakdown voltage will decreases as the electrodes changing from 20 to 100 ?m.The distributions of electrons at electrode diameter of 20 ?m and 100?m are really different.The breakdown with 100 ?m diameter electrodes depend on the initial charges.While using electrodes with 20 ?m diameter,the breakdown depends on the initial and second electrons of cathode.Correspondingly surface charges on dielectric layer in 20 ?m discharge space are much more than that in 100 ?m.So it is much difficult that the breakdown is ignited in20 ?m discharge space than in 100 ?m.Secondly,the influences of dielectric layer on discharge were analyzed.The result show that the breakdown voltage will increasing with increasing the dielectric thickness,also with increasing the roughness of dielectric surface.With thicker dielectric,the breakdown is depended on both initial electrons and second electrons of the cathode.While with a thinner dielectric,the breakdown depends mainly on the initial electrons.The discharges in our simulation are not influenced by the reflection ratio of charged particle on dielectric layer.