A plasma glow discharge and/or dielectric barrier discharge generating assembly (1) comprising at least one pair of substantially equidistant spaced apart electrodes (2), the spacing between the electrodes being adapted to form a plasma zone (8) upon the introduction of a process gas and enabling passage, where required, of gaseous, liquid and/or solid precursor(s) characterized in that at least one of the electrodes (2) comprises a housing (20) having an inner (5) and outer (6) wall, wherein the inner wall (5) is formed from a non-porous dielectric material, and which housing (20) substantially retains an at least substantially non-metallic electrically conductive material.