Synthesis and optical absorption properties of TiO2 nanostructures in SiO2 by sequential implantation of Cu and Ti ions

Optical-grade silica samples were singly or sequentially implanted with 100 keV Cu and 40 keV Ti ions at the same fluence of 1 × 1017 ions/cm2, and were then subjected to furnace annealing in nitrogen ambient. Structure, spatial distribution as well as optical absorption properties of the synthesized nanostructures have been investigated in detail by using various techniques. Our results clearly show that high fluence Ti ion implantation together with subsequent annealing at high temperature could lead to formation of TiO2 nanoparticles with both rutile and anatase phases in SiO2 substrate, which causes an absorption band edge at about 365 nm. The pre-implantation of Cu ion could not only largely enhance growth of the TiO2 nanoparticles during annealing, but also significantly reduce the corresponding band gap energy. Moreover, results from cross sectional transmission electron microscopy measurements demonstrate that the pre-implanted Cu atoms participates into the thermal growth of the TiO2 nanoparticles, which may be responsible for the large redshift of the absorption behavior obtained in the Cu and Ti sequentially implanted SiO2.