Octahedral conversion of a-SiO2 host matrix by pulsed ion implantation

Abstract

The results of measurements of X-ray photoelectron spectra (XPS) of a-SiO2 host material after pulsed implantation with [Mn+] and [Co+, Mn+] ions as well as DFT-calculations are presented. The low-energy shift is found in XPS Si 2p and O 1s core-levels of single [Mn+] and dual [Co+, Mn+] pulsed ion-implanted a-SiO2 (E=30 keV, D=2×1017cm-2) with respect to those of untreated a-SiO2. Similar changes are found in XPS Si 2p and O 1s of stishovite compared to those of quartz. This means that the pulsed ion implantation induces the local high pressure effect that leads to the appearance of SiO6-structural units in a-SiO2 host, forming "stishovite-like" local atomic structure. This process can be described within an electronic bonding transition from the fourfold "quartz-like" to sixfold "stishovite-like" high-pressure phase in the SiO2 host matrix. It is found that such octahedral conversion depends on the fluence and starts with doses higher than D=3×1016cm-2. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.