Chemical States of Implanted Aluminum Ions in Silica and Silicon Ions in Alumina

Aluminum and silicon ions have been implanted in silica glass and α-alumina single crystal, respectively, to doses ranging from 1 × 10¹⁵ to 1 × 10¹⁷ ions·cm^-2. The chemical states of these implanted ions have been studied by X-ray fluorescence spectroscopy. It is found that the implanted aluminum atoms are coordinated only by oxygen atoms, irrespective of implantation dose. On the other hand, the implanted silicon atoms are coordinated only by oxygen atoms at low doses and by both oxygen and silicon atoms at high doses. Although the chemical state of the aluminum atoms is unchanged by heat treatment, that of the silicon atoms is changed toward a less positively charged state. It is inferred that the chemical states of the implanted atoms are controlled by the transport process, although these tend to obey the thermodynamic stability.