  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.
