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

Abstract

The results of measurements of X-ray photoelectron spectra (XPS) of a-SiO 2 host material after pulsed implantation with quartz. This means that the pulsed ion implantation induces the local high pressure effect that leads to the appearance of SiO 6 -structural units in a-SiO 2 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 SiO 2 host matrix. It is found that such octahedral conversion depends on the fluence and starts with doses higher than D ¼ 3Â10 16 cm À2.

Sn-loss effect in a Sn-implanted a-SiO2 host-matrix after thermal annealing: A combined XPS, PL, and DFT study

“…KU-type ("wet" sintering approach) quartz glass was used as a host-matrix for Sn-ion pulsed implantation (see for details Ref. [25]). The following ion-implantation stimulated synthesis was XPS survey (fast wide scan) and core-level analysis of the samples under study were made using a PHI XPS Versaprobe 5000 spectrometer (ULVAC-PHI, USA) with an Al Kα X-Ray source (1486.6 eV) and energy resolution of ΔE ≤ 0.5 eV [25].…”

“…[25]). The following ion-implantation stimulated synthesis was XPS survey (fast wide scan) and core-level analysis of the samples under study were made using a PHI XPS Versaprobe 5000 spectrometer (ULVAC-PHI, USA) with an Al Kα X-Ray source (1486.6 eV) and energy resolution of ΔE ≤ 0.5 eV [25]. As the probing depth of the XPS is approximately 8 Å due to the inelastic mean free path (IMFP) of excited electrons [26], it is quite surface sensitive, being close to that of the total electron yield (TEY) absorption measurements.…”

“…The situation becomes even more exaggerated if the analyzed multi-shell multi-electron element is embedded into a wide-gap insulating material because of the significant differential charging of the sample due to the loss of photoelectrons and the posterior unpredictable driftdischarge. This might be avoided by the short-time multipoint X-ray exposure mode for XPS spectra recording, which was applied with the following summation and averaging of the XPS data obtained [25]. Also the ASTM standards for the XPS measurements were strictly implemented and then additional photoluminescence (PL) probing was performed for additional validation.…”

“…First-principle-based modelling using density functional theory (DFT) was performed to determine the formation energies of various configurations of structural defects induced by Snion implantation of a-SiO 2 and a theoretical description of the electronic structure. These calculations were performed with the use of the SIESTA pseudopotential code [32], a technique that has recently been successful in similar studies regarding impurities in SiO 2 [25]. All calculations were made employing the Perdew-Burke-Ernzerhof variant of the generalized gradient approximation (GGA-PBE) [37] for the exchange-correlation potential in the spinpolarized mode.…”

Ion irradiation induced structural modifications and increase in elastic modulus of silica based thin films

“…A further shift toward lower binding energy is also observed after irradiation with 9 MeV Cu 3+ ions with a fluence of 10 16  ions/cm 2 . However, this shift cannot be solely related to carbon incorporation within the silica network, as the partial transformation of tetrahedrally to octahedrally coordinated silica also decreases the binding energy of silicon due to the higher extra-atomic relaxation energy in octahedrally coordinated silica in comparison with tetrahedrally coordinated silica7475. It should be noted that based on the binding energy of the Si 2p peak, it can be concluded that the concentration of SiC in the films is negligible.…”