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

TL;DR

This study investigates how tin ions behave in amorphous silica matrices after implantation and thermal treatment, revealing two distinct embedding mechanisms and a Sn-loss effect due to structural re-arrangement.

Contribution

It combines experimental XPS and PL analyses with DFT calculations to elucidate the mechanisms of Sn incorporation and clustering in a-SiO2 after thermal annealing, highlighting the Sn-loss phenomenon.

Findings

Sn-embedding occurs via substitution or clustering.

Thermal annealing induces Sn-metal cluster formation.

Sn-loss is linked to host-structure re-arrangement.

Abstract

Amorphous a-SiO2 host-matrices were implanted with Sn-ions with and without posterior thermal tempering at 900 {\deg}C for 1 hour in ambient air. X-ray photoelectron spectroscopy analysis (XPS core-levels, XPS valence band mapping), photoluminescence (PL) probing, and density functional calculations (DFT) were employed to enable a detailed electronic structure characterization of these samples. It was experimentally established that the process of Sn-embedding into the a-SiO2 host occurs following two dissimilar trends: the Sn4+ -> Si4+ substitution in a-SiO2:Sn (without tempering), and Sn-metal clustering as interstitials in a-SiO2:Sn (900 {\deg}C, 1 hour). Both trends were modeled using calculated formation energies and partial densities of states (PDOS) as well as valence band (VB) simulations, which yielded evidence that substitutional defect generation occurs with the help of ion-implantation stimulated translocation of the host-atoms from their stoichiometric positions to the interstitial void. Experimental and theoretical data obtained coincide in terms of the reported Sn-loss effect in a-SiO2:Sn (900 {\deg}C, 1 hour) due to thermally-induced electronic host-structure re-arraignment, which manifests as backward host-atoms translocation into stoichiometric positions and the posterior formation of Sn-metal clusters.