Protective and/or diffusion barrier layer

The invention relates to a chemical, mechanical and/or optical protective and/or diffusion barrier layer ( 16 ) disposed on a metal or plastic substrate ( 14 ). Said layer consists of an organic layer matrix ( 10 ) with metal-containing particles ( 12 ) dispersed therein said metal-containing organic layer ( 16 ) being plasma-polymerized starting from at least one hydrocarbon which can be substituted and one metal-containing component. The protective and/or diffusion barrier layer ( 16 ) is used in a thickness (d) in the submicron range and contains metal particles ( 12 ) finely dispersed therein, that have a grain size that lies below 50% of the layer thickness (d). The organic layer matrix ( 10 ) is deposited by plasma polymerization from a process gas that comprises at least one hydrocarbon that can also be substituted and one metal-containing component and/or an inorganic gas in a reactor that can be evacuated. During the progression of the process organic monomers having different polarities and/or metal-containing components having different concentrations can be introduced into the reactor. The protective and/or diffusion barrier layer, ( 16 ) is for example used as anticorrosive layer of metal substrates ( 14 ) or as a flexible diffusion barrier with an adjustable electroconductivity for plastic packagings. The inventive method is inter alia used for providing fibers, whiskers and rods with an electroconductive coating.