The effects of strain and atomic mobility on the amorphization of Al by Mn implantation at RT

The crystalline to amorphous phase transformation was studied by performing Mn implantations into Al thin films and single crystals at RT. Structural changes and the lattice site occupation of the Mn atoms were directly observed as a function of Mn concentration by X-ray diffraction, Rutherford backscattering (RBS) and channeling experiments. A detailed analysis of the strain distribution upon implantation is given taking into account the lattice site occupation of the Mn atoms and the atomic mobility during implantation at RT. At Mn concentrations 1–2 at% the mainly substitutionally incorporated Mn atoms distort the Al lattice considerably. These distortions provide the driving force for local lattice rearrangements that lead to the formation of amorphous clusters. Experimental results are further consistent with the assumption that the atomic density of these amorphous clusters is equal to the fcc value thus minimizing the strains after transformation. From the results it is concluded that the strain energy is the single most important factor in the amorphization process, determining both the instability of the supersaturated solid solution and the transformation to the amorphous state.