Cross-sectional TEM investigation of tin-implanted SiO2 glass

We report on 300 kV Sn+-implantation into high purity silica substrates at liquid nitrogen and room temperature. The evolution of the Sn depth profiles in dependence on subsequent heat treatments was monitored by cross-sectional transmission electron microscopy, energy-dispersive X-ray spectrometry analyses, and Rutherford backscattering spectrometry. Using selected-area electron diffraction, the existence of nanocrystalline β-Sn particles could be proved in the as-implanted state independent on the substrate temperature during implantation. After subsequent exposure to 873 K for 1 h, the upper part of the tin distribution becomes oxidised, whereas the deeper fraction of tin nanocrystallites undergoes a coarsening resulting into several 10 nanometer large, spherical β-Sn crystals. If the implantation is followed by a heat treatment at 1373 K for 6 h, tin is entirely oxidised and its distribution is shifted further towards the surface.