Preparation And Investigation Of Optical Properties Of TiO₂Thin Films

TiO2is not only a semiconductor with a wide band gap of3.2eV, but also a good optical material which has many excellent photoelectric properties and physicochemical properties. TiO2films have many applications in many fields, such as oxygen gas sensors, optical waveguides, upconversion luminescence, radiation and UV radiation and absorption, surface modification, solar cells, etc. Although it’s a semiconductor used earlier, it will attracts researcher’s enthusiasm again, as it’s potential value in surface modification, Green degradation, optical waveguide and luminescence fields。In the present work, TiO2films were deposited on quart glass(SiO2)substrate by radio frequency magnetron sputtering, and the structure surface appearance, elements, film thickness, optical properties were investigated by using many analytical instruments, such as AFM,XRD,RBS, spectrophotometer, etc. The main content of the work are as follows:At first, the structural and optical properties of TiO2films were investigated by changing the depositing pressure. XRD showed that higher quality films of rutile phase should be deposited under the condition of higher working pressure. When the working pressure became higher,the crystal quality of films were enhanced at first, smooth later,it reached the best at2.0Pa.RBS shows that the higher sputtering pressure is,the lower deposition rate is. High sputtering pressure is not conductive to the as-grow films. It’s not difficult to realize that the best pressure condition to grow TiO2films with rutile phase is1.5Pa.Secondly, XRD diffraction spectra was applied to investigating the crystallize properties of films by changing the substrate temperature. It shows that temperature do a lot to the crystal properties of films.when the annealing temperature changes from25℃to500℃,films under this temperature cannot crystallize, but when the annealing temperature reaches to1000℃,the films shows the rutile phase (110) crystal orientation. We should pen attention to the substrate materials as it may melt and crystallize when the films annealed at a high annealing temperature, which do harm to the crystallization of films.Thirdly, we investigated the effect of oxygen and argon gas flow ratio on the structural and optical properties of TiO2films by XRD、AFM and spectrophotometer. The structural properties of the films were investigated by XRD and AFM techniques. The XRD results indicate that all of the samples are amorphous, and the AFM results indicate that different oxygen and argon gas flow ratio produced TiO2films of different surface morphology, films deposited at the condition of O2:Ar=1:24have the lowest RMS roughness. The optical properties of TiO2films was measured by a spectrophotometer, From the refractive index dispersion diagram and extinction coefficient dispersion diagram, We can conclude that different Oxygen and argon gas flow ratio produce TiO2films with different refractive index but the same extinction coefficient, the lower condition of Oxygen and argon gas flow ratio is, the higher refractive index of films are.Fourthly, we investigated the effect of substrate temperature on the structural and optical properties of TiO2films. XRD is applied to investigated the structural properties of the films It indicates that all of the samples are amorphous, and the AFM result indicate that substrate temperature influences the surface morphology, films deposited at the condition of higher substrate temperature have the lower RMS roughness. The optical properties of TiO2films was measured also by a spectrophotometer result shows that TiO2films deposited at higher substrate temperature have the higher refractive index。Rising the substrate temperature is useful to grow films with high refractive index.Finally, we investigated the effect of sputting power on the structural and optical properties of TiO2films. By means of XRD diffraction spectra and AFM, the structure and crystal quality of films are analyzed. Results show that all of the samples are amorphous, and the sputting power influences the surface morphology, films deposited at higher sputting power have the lower RMS roughness. By means of a spectrophotometer, the optical properties of TiO2films are measured Result shows that TiO2films deposited at higher sputtering power have the higher refractive index.