Observation of overpressurized bubbles in helium‐irradiated aluminium films

Aluminium polycrystalline thin films implanted with high doses of He+ ions are studied by electron microscopy and by X‐ray and electron diffraction. With increasing He+ dose, the radius of the electron diffraction rings is observed to increase markedly indicating a homogeneous and isotropic decrease of the aluminium lattice parameter over the implanted region. The overall data seem to support the idea that most of the implanted He atoms precipitate into bubbles and subject the surrounding metal matrix to an average compression which, at higher doses, may reach several hundred kilobars. Copyright © 1979 WILEY‐VCH Verlag GmbH & Co. KGaA