A system for forming a thin film on a substrate uses a plasma to activate at least one gaseous precursor in a plasma generator fluidly coupled with a reaction space. The plasma generator is operative to generate a plasma from at least a portion of the precursor gas with at least one pair of plasma electrodes, one plasma electrode having a non-native electrically conductive adlayer exhibiting property characteristics that cause the adlayer to be substantially conserved and chemically active with at least one of the gases present within the plasma generation region.