Plasma driven superpermeation of hydrogen through group Va metals

A barrier for the absorption of hydrogen molecules generated by a nonmetallic film on a metal surface may result in superpermeation of suprathermal hydrogen particles. Virtually all the sticking or implanted particles may permeate through the metallic membrane, with a permeation flux depending neither on the metal temperature nor on its thickness. Niobium and vanadium membranes with oxicarbide monolayer films were immersed in a hydrogen plasma in order to study their interaction with hydrogen ions in the energy range from a few eV to 250 eV, controlled by changing the membrane bias. A stable superpermeation flux was observed up to ion energies of tens of eV without special efforts to maintain the surface film. We found that the nonmetal monolayer film remains absolutely stable under the sputtering, including chemical sputtering, by hydrogen particles of energy less than ≈50 eV. Thus superpermeability appears to be an intrinsic feature of the investigated systems of “nonmetallic film–metal–hydrogen particles of energy lower than 50 eV.”