Ion beam analysis of nanoporous surfaces produced by He-implantation and oxidised by plasma-immersion ion-implantation

Helium ion implantation into metals can lead to ordered bubble structures that develop into nanoporous cavity structures at high dose levels. Such cavity structures, and the oxides that can be formed on them, have been investigated previously for materials implanted using ion accelerators. These materials have unique features that offer potential for applications. Here, we investigate pulsed plasma-immersion ion-implantation (PI3 TM) a a means of forming nanoporous oxide surfaces on a larger scale. 40 keV helium, and 20 keV oxygen, is implanted into Ti metal and two Ti alloys (including Ti-6Al-4V), and NRA, RES, HERDA, TEM and Raman spectroscopy are used to characterise the resulting cavity structure and surface oxides. He implantation at a temperature of 160 degrees C produces cavities,similar to 2 nm across, in close-packed, apparently random structures. Oxygen implantation into substrates that are not pre-implanted with He, causes significant formation of TiO2 (rutile). Pre-implantation with He causes an increase in the amount of oxide and in the proportion of oxide that is amorphous. (C) 2000 Elsevier Science B.V. All rights reserved.