X-ray investigation of amorphization of ion-implanted Al-Mn

Structural modifications of Al thin films implanted with Mn+ ions at liquid-nitrogen-temperature (LNT) (similar to 77 K) were studied by X-ray powder diffraction. For each Mn concentration, strain and crystallite size were determined from X-ray line broadening For room-temperature (RT) implantation, amorphization begins at approximately 1 at.% Mn by thermally activated local atomic rearrangements which lead to the formation of amorphous zones or clusters. At LNT, a supersaturated solid solution is formed at mean Mn concentrations below 5 at.% Mn. At higher Mn concentrations, amorphous clusters formed throughout the sample in regions where the strain level reached a threshold value at a critical Mn concentration of 8.5%. Present investigations suggest a preferential short-range migration of Mn atoms from the remaining crystalline material to amorphous regions formed at LNT causing an Mn depletion and partial recovery of the crystalline regions. The maximum value of the atomic displacements U-st was found to be 0.13 +/- 0.01 Angstrom and the maximum value of the strain was (1.65 +/- 0.15) x 10(-3). The lattice constant a(0) of the host (Al) lattice was found to decrease by about 0.13%. (C) 1999 Elsevier Science B.V. All rights reserved.