The oxidation kinetics of Mg-, Si- and Fe-implanted aluminum by using X-ray photoelectron spectroscopy

The oxidation kinetics of Mg-, Si- and Fe- implanted aluminum has been stud ied at room temperature and a water vapour pressure of 2.0 x 10(-6) Pa usin g X-ray photoelectron spectroscopy. The elements Mg, Si and Fe were implant ed into pure aluminum at low ion doses from 6.0 x 10(12) to 3.6 x 10(13) io ns cm(-2). Secondary ion mass spectrometry (SIMS) depth profiles have shown that the element distributions of Mg and Fe in aluminum are consistent wit h the theoretical depth profiles calculated using a TRIM program. The impla nted elements are distributed in the near surface region with their maximum concentration at a depth of similar to 50 nm. In the case of implanted Si, however, the SIMS depth profile shows no maximum concentration peak, and t he near-surface concentration is much higher than that calculated. This is ascribed to diffusion of Si toward the surface during implantation. The oxi dation kinetics of implanted aluminum have shown that surface concentration s of implanted Si, as low as 40 ppm, cause an increase in the Al oxidation rate compared to the pure metal. By contrast, equivalent concentrations of implanted Mg in aluminum result in a lowered oxidation rate until the oxide reaches a thickness of 3 monolayers, after which a rapid increase in oxida tion occurs. Implanted Fe in the same concentration range does not cause an y change in oxidation rate of aluminum. These oxidation kinetics can be exp lained on the basis of metal vacancies in the defect structure of aluminum thin oxide films. The effects of surface damage caused by ion beam during t he implantation experiment were also determined by measurements of oxidatio n kinetics. (C) 1999 Published by Elsevier Science B.V. All rights reserved .