Most chemical reactions do not occur spontaneously, i.e. simply by mixing the reaction partners. In the majority of cases, an energy supply is required as activation energy even if the reaction is "exothermic", i.e. if energy is released over the entire course of the reaction. Energy is generally supplied by increasing the temperature. In all the above cases, the chemical reaction thus coincides with a – usually significant – temperature increase. This is problematic if the chemical reaction is to take place on a temperature-sensitive substrate. In the low-pressure plasma, there is no or almost no temperature increase due to the excitation. In case of HF excitation, ions, radicalsand excited atoms remain largely cold (also refer to ⇒ cold plasma) while being highly reactive, e.g. reacting spontaneously with other particles to form new bonds. Therefore, one of the great benefits of plasma chemistry is the absence of thermal stress on temperature-sensitive substrates.