Octahedral conversion of a-SiO sub(2) host matrix by pulsed ion implantation

The results of measurements of X-ray photoelectron spectra (XPS) of a-SiO sub(2) host material after pulsed implantation with [Mn super(+)] and [Co super(+), Mn super(+)] 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 super(+)] and dual [Co super(+), Mn super(+)] pulsed ion-implanted a-SiO sub(2) (E=30 keV, D=210 super(17)cm super(-2)) with respect to those of untreated a-SiO sub(2). 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 SiO sub(6)-structural units in a-SiO sub(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 sub(2) host matrix. It is found that such octahedral conversion depends on the fluence and starts with doses higher than D=310 super(16)cm super(-2).