HIGH-FLUENCE ION-IMPLANTATION OF IN INTO AL CRYSTALS - FORMATION AND EVOLUTION OF BURIED LAYERS

Al(110) single-crystal samples were implanted at T = 200 degrees C wit h 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 prec ipitates growing with fluence in topotactical alignment with the host matrix. High-fluence implantation was used in an attempt to produce si ngle-crystal buried layers of In embedded into Al. Rutherford back-sca ttering (RBS)-channelling analysis of the implanted samples and transm ission electron microscopy studies of the incorporated In layer morpho logy were carried out. With increasing fluence the peak In concentrati on 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). Th e buried layer thus formed was found to have fragmentary morphology co nsisting os large In precipitates. During further implantation the pea k concentration decreased drastically to reach a steady state; In orde r to study a possible effect of sputtering on the In profile evolution , sputtered atoms were collected in situ on carbon foils during implan tation. The foils were subsequently analysed by RES analysis to determ ine the partial sputtering yields for In and Al independently. Both pa rtial sputtering yields were found to change with fluence. The evoluti on of the In depth distribution profile showed that the high peak conc entrations are achieved as a result of competition between the diffusi on of the implanted indium and matrix surface erosion due to sputterin g.