[en] The surface and sub-surface regions of silicon and a range of titanium- and vanadium-based metals have been modified by implantation of helium at energies of 20-50 keV, using the Plasma Immersion Ion Implantation (PI³) facility at ANSTO. In the case of silicon, the resulting structure has been altered further, either by thermal annealing, or by thermal annealing following the application of a thin, sputtered, film of gold onto the surface. For the metals, the implanted structure has been oxidised in several ways; thermally, anodically, and by plasma implantation. Surfaces modified in these ways might be expected to have unique chemical and physical properties. They have been investigated by a range of techniques including electron microscopy, Raman spectroscopy, Rutherford backscattering spectrometry, and nuclear reaction analysis. The structure and phases of oxides developed on plasma-implanted metals are compared with those on unimplanted, but otherwise identically treated, metals. Corresponding results for helium-ion implantation at higher energies are also presented. It is shown that implantation can affect the blend of oxide phases at the surface and the degree of oxidation