Analysis of (TiO2)X(Ta2O5)1-X composite films prepared by radio frequency ion beam sputtering deposition

Chien-Jen Tang; Yung-Chi Wu; Cheng-Chung Lee

doi:10.1117/12.676233

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28 August 2006 Analysis of (TiO₂)_X(Ta₂O₅)_1-X composite films prepared by radio frequency ion beam sputtering deposition

Chien-Jen Tang, Yung-Chi Wu, Cheng-Chung Lee

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Proceedings Volume 6286, Advances in Thin-Film Coatings for Optical Applications III; 628603 (2006) https://doi.org/10.1117/12.676233
Event: SPIE Optics + Photonics, 2006, San Diego, California, United States

Abstract

Using two or more materials to deposit a composite film has an advantage to get a film with desired refractive index. Besides, its optical property and mechanical property are better than a film deposited by a single material. In this study, (TiO₂)_X(Ta₂O₅)_1-X composite films have been prepared by a radio frequency ion beam sputtering deposition (RF-IBSD) where x was determined by the area ratio of titanium to tantalum targets. The optical constants of (TiO₂)_X(Ta₂O₅)_1-X composite films were calculated from their spectra by using envelope method. The refractive indices ranged from 2.481 to 2.165 at 550nm, and the extinction coefficients were lower than 1x10^-3 for wavelength in the ranges of 400nm to 600nm and lower than 1x10^-4 for wavelength longer than 600nm. The surface roughness of all composite films was about 0.1nm. The stress decreased from -520MPa for pure TiO₂ film to less than -280MPa for the composite films as measured by a phase-shift Twyman-Green interferometer. When the content of TiO₂ was less than 79.5%, the composite films were amorphous even post-baked to 400°C as measured by x-ray diffraction. The composite films mixed with TiO₂ and Ta₂O₅ can improve thermal stability and reduce extinction coefficient and stress. Composite films can replace the conventional high refractive index layer prepared by a single material to fabricate multilayer filters, and it is also suitable for high temperature applications, such as high reflection coating of projector lamps.

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Chien-Jen Tang, Yung-Chi Wu, and Cheng-Chung Lee "Analysis of (TiO₂)_X(Ta₂O₅)_1-X composite films prepared by radio frequency ion beam sputtering deposition", Proc. SPIE 6286, Advances in Thin-Film Coatings for Optical Applications III, 628603 (28 August 2006); https://doi.org/10.1117/12.676233

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