Oxidation Kinetics of Mg-, Si-, and Fe-Implanted Aluminum by Using X-ray Photoelectron Spectroscopy

Abstract

The oxidation kinetics of Mg-, Si-, and Fe-implanted aluminum has been studied at room temperature and a water vapor pressure of 2.0 {times} 10{sup {minus}6} Pa using X-ray photoelectron spectroscopy. The elements Mg, Si, and Fe were implanted into high-purity aluminum at low ion doses from 6.0 {times} 10{sup 12} to 3.6 {times} 10{sup 13} ions {center_dot} cm{sup {minus}2}. Secondary ion mass spectrometry (SIMS) depth profiles have shown that the element distributions of Mg and Fe in aluminum are consistent with the theoretical depth profiles calculated using a TRIM (transport of ions in matter) program. The implanted elements are distributed in the near-surface region with their maximum concentration at the depth of {approximately} 50 nm. In the case of implanted Si, however, SIMS depth profile shows no maximum concentration peak and the near-surface concentration is much higher than that calculated. This is ascribed to diffusion of Si toward the surface during implantation. Oxidation kinetics of implanted aluminum have shown that surface concentrations of implanted Si, as low as 40 ppm, cause an increase in the Al oxidation rate compared to the pure metal. By contrast, implanted Mg, surface concentration from 20 to 120 ppm, results in a lowered oxidation ratemore » until the oxide reaches a thickness of {approximately}0.55 nm, and after that a rapid increase in oxidation occurs. Implanted Fe does not cause any change in the oxidation rate of aluminum. These oxidation kinetics can be explained on the basis of metal vacancies in the defect structure of aluminum thin oxide films. The effects of surface damage caused by the ion beam during the implantation experiment were also determined by measurements of oxidation kinetics.« less