An attempt to make a buried layer of indium in aluminium by ion implantation

Abstract

High-fluence ion implantation of 270 keV indium into aluminium single crystals were performed in an attempt to form buried layers. Indium and aluminium were chosen because of their low mutual solubility and the ability to form indium inclusions during implantation. Ion implantation and Rutherford backscattering (RBS) analysis were done in situ. A 540 keV He 2+ beam was used for RBS and channeling analysis of the crystals. The results show that by implanting in steps at elevated temperatures a higher peak concentration can be reached and this is essential in formation of buried layers. Peak concentrations as high as 43 at.% have been reached. The tabulated value of the sputtering coefficient for this system was found to be about 8, while weight loss measurements revealed a sputtering coefficient ∼3. Simulations of the experimental results show that if sputtering is the only effect considered the yield has to be as low as 1 in order to get the same depth profiles. This indicates that indium inclusions coalesce at the average ion range during annealing inducing a barrier effect.