Synthesis, Structure And Optical Properties Of Nanomaterials Embedded In SiO₂ By Zn And Ti Ion Implantation

TiO₂ is an important semiconductor material with advantages of high chemical and thermal stability,non-toxicity,super-hydrophilic property,and so on,which are widely used in the fields of solar cells,photocatalysis,self-cleanness glass,sunscreen cream and coating.Among various synthetic methods for nanomaterials,ion implantation has been widely used on account of its controlled energy and fluence.Especially,for the sequential implantation of Ti ions with other non-metal or metal ions,not only TiO₂ can be synthesized,but also it may realize the response to visible light and thus the photocatalytic efficiency under solar light irradiation could be enhanced.In this thesis,single or sequential implantation of Zn and Ti ions into SiO2 combining with post annealing has been employed to fabricate nanomaterials and the structure,surface morphologies as well as the optical properties have been studied in detail by kinds of analysis and test methods.The implanted samples were: Zn ions with energy of 70 keV were firstly implanted into amorphous SiO2 at fluences of 1×1016,3×1016,6×1016 ions/cm2,and then the Zn implanted samples were implanted with Ti ions at energy of 45 keV and fluence of 1×1017 ions/cm2.Also only Zn or Ti ion implanted samples were prepared under the same conditions,and its fluences were 6×1016,1×1017 ions/cm2,respectively.The main results and conclusions are as follows:?1?The influences of Zn ion pre-implantation on the microstructure,surface morphologies and optical absorption properties of the formed nanomaterials after high temperature annealing were discussed.It has been found that TiO₂ nanoparticles with rutile phase could be formed after high temperature annealing with its absorption edge at about 380 nm for single Ti ion implantation sample.While for Zn ions pre-implanted samples,large size TiO₂ nanorods could be observed with absorption edge red shifted to about 450 nm.Meanwhile,transformation of amorphous SiO2 into crystalline SiO2 for Zn and Ti ions sequential implantation samples has also been found after high temperature annealing.?2?The samples which were implanted with single Ti ion and low fluence of Zn ion pre-implantation?1×1016 ions/cm2?were selected for thermal annealing in nitrogen atmosphere to study the structure,morphologies and optical properties of the formed nanostructures.Our results clearly show that rutile TiO₂ nanoparticles were formed in both the prepared samples after annealing in nitrogen ambient,which present no significant difference in their structure,morphologies and optical properties.?3?The samples implanted with high fluences of Zn/Ti ions and singly implanted with Zn and Ti ions were annealed in oxygen atmosphere under lower temperature.The properties of optical absorption and photoluminescence of the formed ZnO-TiO₂ composites after annealing have been discussed.Our results demonstrate that although TiO₂ nanoparticles could be formed in Ti ion singly implanted SiO2 substrate after low temperature annealing,no photoluminescence peak could be detected owing to fact that the formed TiO₂ nanoparticles exhibits amorphous structure.As for Zn and Ti ion sequentially implanted samples,a PL peak at about 380 nm with intensity much higher than that found in Zn ion singly implanted sample under annealing at the same conditions was observed.