Detachment of alumina films from aluminium by 100 keV H+ ions

Irradiation of aluminium covered by anodic oxide films 3–14 nm thick using 100 keV H+ ions is shown to result in detachment of the oxide film. A dose of 6.6 × 1016 H+ ions cm−2 on a 6.5 nm thick film causes the removal of large pieces of oxide with dimensions at least 15 µm. Atomic force microscopy analysis shows that the location of the failure is within ∼1 nm of the metal/oxide interface. The large aspect ratio (width to thickness) of the detached pieces is thus ∼2000 : 1 and indicates that there is a disruption of the oxide bonding over large areas. The bombardment also results in the formation of blisters with diameters up to several hundred nanometres in the oxide, accompanied by shallow depressions, ∼5 nm deep in the underlying metal. The detachment is suggested to be associated with either condensation of vacancies generated in the metal by the H+ ions or accumulation of hydrogen atoms deposited in the metal by the ion beam in the region of the metal/oxide interface. Although the beam energy and dose were expected to cause some disruption in the implanted material, the complete detachment of large areas of oxide was not anticipated. In fact, this appears to be the first time such gross detachment of an anodic film by H+ ion irradiation has been reported