Calculation of the uniform breakdown field strength of SF/sub 6/ gas

We calculated the uniform dielectric breakdown field strength of SF/sub 6/ gas over the temperature range of 300 to 3000 K. The local thermal equilibrium (ITE) composition of the dissociated gas is connected to the electron impact collision cross sections of the species SF/sub 6/, F/sub 2/, F and S. The critical reduced electric field strength of the composition is determined by a balancing electron generation and loss modeled by chemical reactions evaluated by the electron energy distribution function (EEDF) derived from the Boltzmann transport equation. At room temperature, pure SF/sub 6/ has a critical reduced electric field strength of 362 Td. With increasing temperature and decreasing density we found a small decrease of this value, whereas at temperatures higher than 1500 K, dissociation starts to decrease the dielectric strength of the composition. Furthermore, we found that generation of electrons by (associative) detachment from F/sup -/ starts to play an important role at temperatures >2500 K, where the critical field strength still has a value of 118 Td. This value is found to decrease rapidly afterwards with increasing temperature to the value of 38 Td at 3000 K. The calculated results agree very well with independently predicted values and measured data.