A particle-in-cell simulation of the breakdown mechanism in microdischarges with an improved secondary emission model

In this paper, the failure of the breakdown voltage from the Paschens law at extremely small electrode separations is studied. The electrical breakdown in microgaps occurs at the voltages far below the Paschen curve minimum breakdown limit and the modified Paschen curve should be used. Offered explanation for the departure from the Paschens law at small gap spacings is based on the increasing of the yield of the secondary electrons. The high electric fields existing in small gaps may enhance the secondary electron yield and this would lead to a lowering of the breakdown voltage and to the departure from the Paschens law. Particle-in-cell/Monte-Carlo (PIC/MCC) simulations with a new secondary emission model have been performed to estimate the importance of this mechanism in the discharge breakdown. Obtained simulation results suggest that deviations from the Paschen curve across the micron and submicorn gap spacing can be attributed to the ion-enhanced field emissions. (c) 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim