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

TL;DR

This study demonstrates that pulsed ion implantation can induce a local high-pressure phase transition in a-SiO2, transforming its structure from quartz-like to stishovite-like octahedral units, depending on ion dose.

Contribution

It reveals that pulsed ion implantation causes a high-pressure phase transition in a-SiO2, forming stishovite-like structures, a novel insight into ion-induced structural modifications.

Findings

High-energy ion implantation induces local high-pressure effects.

Transition to stishovite-like structure occurs above a dose of 3×10^16 cm^-2.

XPS spectra show shifts consistent with octahedral SiO6 units.

Abstract

This is the 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*10^17 cm^-2) with respect to those of untreated a-SiO2.The 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 which leads to an appearance of SiO6-structural units in alpha-SiO2 host, forming "stishovite-like" local atomic structure. This process can be described within electronic bonding transition from the four-fold "quartz-like" to six-fold "stishovite-like" high-pressure phase in SiO2 host-matrix. It is found that such octahedral conversion depends on the fluence and starts with doses higher than D = 3*10^16 cm^-2.