Hybrid modeling of a capacitively coupled radio frequency glow discharge in argon: Combined Monte Carlo and fluid model

A hybrid model has been developed for a capacitively coupled rf glow discharge in argon, employed as a spectroscopic source in the field of analytical chemistry. The cell is a rather small cylinder with a very small rf-powered electrode (only 5 mm in diameter). The typical working conditions applied for analytical spectroscopy are a gas pressure of 6 Torr and incoming power of 10 W. The hybrid model consists of a Monte Carlo model for the electrons and a fluid model for the electrons and argon ions. The latter model also contains Poisson's equation, to obtain a self-consistent electric-field distribution. The input values for the model are the gas pressure, the discharge power, the cell geometry and the collision cross sections. The typical calculated results include the rf and de bias voltage, the electrical current at the rf electrode, the potential distribution, the density of argon ions and electrons, the electron energy-distribution function and information about the collision processes of the electrons. These results are presented throughout the discharge cell and as a function of lime in the rf cycle. Moreover, we have investigated how many rf cycles have to be followed with the Monte Carlo model before a periodic steady stare is reached.