AN ATTEMPT TO MAKE A BURIED LAYER OF INDIUM IN ALUMINUM BY ION-IMPLANTATION

High-fluence ion implantation of 270 keV indium into aluminium single crystals were performed in an attempt to form buried layers. Indium an d aluminium were chosen because of their low mutual solubility and the ability to form indium inclusions during implantation. Ion implantati on and Rutherford backscattering (RES) analysis were done in situ. A 5 40 keV He2+ beam was used for RES and channeling analysis of the cryst als. The results show that by implanting in steps at elevated temperat ures 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 f or this system was found to be about 8, while weight loss measurements revealed a sputtering coefficient similar to 3. Simulations of the ex perimental results show that if sputtering is the only effect consider ed the yield has to be as low as 1 in order to get the same depth prof iles. This indicates that indium inclusions coalesce at the average io n range during annealing inducing a barrier effect.