Optical Properties Of (1-x) TiO₂-xTa₂O₅ Films Prepared With Ion-aided Electron Beam Evaporation

New optical and optoelectronic devices require properties of thin films which are not possible to be achieved by using existing materials. Mixing two or more materials allows the possibility to change many properties of the thin films, such as refractive index, extinction coefficient, microstructure, stress, resistively, surface roughness, etc. TiO₂-Ta₂O₅ thin films are new-style optical thin films that made of uniform mixing compound as starting material. It has been widely used in anti-reflection coatings, interference filters, DRAM devices, photochemical catalysis etc. There are large science and application values to study the structure and properties of TiO₂-Ta₂O₅ thin films.The (1-x)TiO₂-xTa₂O₅ compound thin films were prepared by IAD on K9 glasses with Ta₂O₅ and TiO₂ of different proportioning as starting materials, the deposition parameters are shown below: the base pressure were (2-3)×10^-3Pa; the substrate temperatures were 200℃; the deposition rates were 5A|°/s; oxygen flux were 18sccm; the thickness of films were 300nm; post-annealing of thin films was run under air condition at 500℃for 2 hour, and cooled with furnace cooling. The crystal structure and surface morphology is determined by XRD and AFM, respectively. The structure of (1-x)TiO₂-xTa₂O₅ films are amorphous as deposition, after annealing the structure is anatase crystallized, and the crystallinity is decresed with increasing Ta₂O₅ content, it was observed that Ta₂O₅ retarded amorphous-to-anatase transformation; the magnitude order of grain size are all nanometer, and the grain size normal to plane (101) are reduced with increasing Ta₂O₅ content; the growth formation of all the films are like columniation, the average size and the surface roughness decreased gradually with increasing Ta₂O₅ content; after annealing average grain size of thin films is larger than that of before annealing.Transmittance spectra of thin films were measured by spectrophotometer, optical constants of the films have been calculated by the envelop method. The indirect band gap can be determined by Tauc relationship. The average transmittance is high within visible light region and enhanced with increasing Ta₂O₅ content; the refractive index varies from 1.80 to 2.07, the magnitude order of extinction coefficient is about 10^-3～10^-4; before annealing the optical band gap of films increased from 3.266eV to 3.417eV along with the content of Ta₂O₅ enhanced from 0 to 20%; after annealing the optical band gap of films increased from 3.227eV to 3.512eV along with the content of Ta₂O₅ enhanced from 0 to 20%, the optical band gap and the grain size of the films are accord with Kayanuma model.