The non-thermal behavior of low pressure unloadings is characterized by the reciprocal effect of cold neutral particles and ions with
relatively hot electrons, whereby the electron energy distribution function (EEDF) is strongly affected by the way of heating,
the plasma composition and in general substantially deviates from a maxwell distribution. On the other hand the
distribution function determines the formation of reactive radicals, which represent the actual carriers of plasma chemistry.
The goal of this project is to understand this mutual dependence better and thus open possibilities of affecting the plasma
characteristics (e.g. regarding the preferential production or suppression of certain species) in a controlled way. For this purpose if
possible detailed measurements of the plasma composition and the EEDF are to be accomplished with different filling gases and unloading
conditions, which then can be used as initial and control parameters for appropriate semi analytic and numeric model calculations.
The central topic of this subproject is the reciprocal effect of cold neutral particles and ions with relatively hot electrons in
reactive low pressure plasmas. The physically relevant size for the description of this reciprocal effect is the electron energy
distribution function (EEDF), whose form is determined both by the kind of the plasma heating as well as by (species- and energy-dependent)
impact cross sections.
Dissociative impact processes lead to the formation of radicals and new chemical reaction products, which change the composition of the
plasma, until a stationary condition adjusts itself with respect to the unloading characteristic EEDF and species distribution. A
purposeful influence of the EEDF would make it possible to intervene in this species distribution and control the plasma characteristics
regarding certain questions or applications.