Modelling of low–pressure gas breakdown in uniform DC electric field by PIC technique with realistic secondary electron emission M. Radmilovi´ c–Radjenovi´ c, Z. Lj. Petrovi´ c, G. N. Malovi´ c, D. Mari´ c Institute of Physics, P. O. Box 57, 11001 Belgrade, Serbia and Montenegro e–mail: marija@phy.bg.ac.yu, zoran, malovic, draganam@phy.bg.ac.yu B. Radjenovi´ c Vinˇ ca Institute of Nuclear Sciences, P. O. Box 522, Belgrade, Serbia and Montenegro Received 27 April 2006 This paper compares the basic phenomenological model based on the Townsend’s the- ory and the detailed simulation of the gas breakdown in argon in uniform DC electric field. Calculations were carried out by using a one–dimensional particle–in–cell/Monte Carlo (PIC/MCC) code with three velocity components with a new secondary emission model. The simulation results clearly show how different models of the secondary electron emission affect the breakdown voltage. The fact that results of simulation are in a good agreement with the available experimental data merely means that phenomenological se- condary electron yields were developed to fit the experiment. However, oversimplified models cannot predict all features of Townsend discharges and cannot be reconciled with binary collision data. One such example is the need to predict the DC volt–ampere cha- racteristics in order to reveal the predominant physical processes by studying the j/p 2 scaling. PACS : 52.25.Jm Key words : breakdown voltage, secondary electron emission, simulations 1 Introduction The understanding and control of electrical breakdown across the interelec- trode gap is critically important both for a deeper understanding of fundamental plasma behavior and for industrial applications. Ignition of the DC glow discharge represents one of the oldest problems in the study of low–pressure gas discharges [1]–[3]. At the same time, DC and pulsed DC discharges are widely applied in the microelectronics industry, in plasma display panels, for depositing thin films, for semiconductor processing, surface modification, waste treatment, etc. [4], [5]. In large scale systems, the experimentally observed Paschen law has been suc- cessfully explained by the Townsend theory [6]. Paschen curves dictate the break- down voltage for a particular gas as a function of the pd (pressure p times electrode distance d) product. This breakdown voltage curve represents a balance between the number of electrons lost by diffusion and drift in the inter–electrode gap and the number of secondary electrons generated at the cathode [7]. The breakdown voltage B996 Czechoslovak Journal of Physics, Vol. 56 (2006), Suppl. B