Surface modification of aluminium by plasma immersion ion implantation

Nitrogen plasma immersion ion implantation (PIII) into pure aluminium was performed at voltages of -10 to -30 kV. Different temperatures, from 250 to 500 degrees C and incident fluences of 1.2-3.6 X 10(18) nitrogen atoms/cm(2) were used to investigate the diffusion behaviour and AIN phase formation. X-Ray diffraction (XRD) shows the formation of cubic AIN at temperatures below 300 degrees C, whereas hexagonal AIN appears beyond 390 degrees C. No observable diffusion was measured, using ion beam techniques, at temperatures below 300 degrees C, limiting the retained dose to approximately 10% of the incident ion flux. At higher temperatures, thermally activated diffusion with an activation energy of approximately 1 eV leads to an inward diffusion, albeit not the formation of thick stoichiometric ALN layers. The retained dose is increased to approximately 35% for 500 degrees C and a fluence of 1.2 X 10(18) nitrogen atoms/cm(2). A long diffusion tail of nitrogen, below the solubility limit is detectable with SIMS, correlated with a lattice expansion of the native Al by approximately 0.7%. (C) 2000 Elsevier Science S.A. All rights reserved.