High-fluence ion implantation of In into Al crystals: formation and evolution of buried layers

摘要

Al(110) single-crystal samples were implanted at T = 200 degrees C with In+ ions of 250 keV energy with fluences ranging from 4 x 10(20) to 3 x 10(21)m(-2). The implantation resulted in the formation of In precipitates growing with fluence in topotactical alignment with the host matrix. High-fluence implantation was used in an attempt to produce single-crystal buried layers of In embedded into Al. Rutherford back-scattering (RBS)-channelling analysis of the implanted samples and transmission electron microscopy studies of the incorporated In layer morphology were carried out. With increasing fluence the peak In concentration was observed to increase gradually until a maximum value of (a)bout 38 at.% was reached at an implantation dose of 1.5 x 10(21) m(-2). The buried layer thus formed was found to have fragmentary morphology consisting os large In precipitates. During further implantation the peak concentration decreased drastically to reach a steady state; In order to study a possible effect of sputtering on the In profile evolution, sputtered atoms were collected in situ on carbon foils during implantation. The foils were subsequently analysed by RES analysis to determine the partial sputtering yields for In and Al independently. Both partial sputtering yields were found to change with fluence. The evolution of the In depth distribution profile showed that the high peak concentrations are achieved as a result of competition between the diffusion of the implanted indium and matrix surface erosion due to sputtering. [References: 30]