| AVS 56th International Symposium & Exhibition | |
| Thin Film | Thursday Sessions |
| Session TF-ThP |
| Session: | Aspects of Thin Films Poster Session |
| Presenter: | Y. Sanno, Aoyama Gakuin University, Japan |
| Authors: | Y. Sato, Aoyama Gakuin University, Japan Y. Sanno, Aoyama Gakuin University, Japan C. Tasaki, Aoyama Gakuin University, Japan N. Oka, Aoyama Gakuin University, Japan T. Kamiyama, AGC Ceramics Co. Ltd., Japan Y. Shigesato, Aoyama Gakuin University, Japan |
| Correspondent: | Click to Email |
Nb-doped anatase TiO2 (Nb:TiO2) films have attracted much attention as indium-free transparent conductive oxide films [1]. Recently, we have reported on electrical and optical properties of Nb:TiO2 films deposited on glass substrate by dc magnetron sputtering using a slightly reduced TiO2-x target with Nb2O5 pellets [2]. In this study, we investigated the effect of Nb doping on the electrical and optical properties of Nb:TiO2 films with comparison of pristine TiO2 films. Anatase TiO2 and Nb:TiO2 films were deposited on unheated quartz glass substrates by dc magnetron sputtering using a slightly reduced TiO2-x (x = 0.014, conductivity: 3.7 Scm-1) and Nb-doped TiO2-x (Nb = 9.5 at.%) targets (AGC Ceramics, Japan). By using these reduced TiO2-x targets, stable dc discharge was maintained because of the sufficient resistivity of the reduced TiO2-x targets to avoid charge up of the target surface and hence to suppress arcing. X-ray diffraction patterns of all the as-deposited films exhibited amorphous structure, while they were crystallized into polycrystalline anatase structure after post-annealed in vacuum (6×10-4 Pa) at 500-600 oC for 1 hr. Electron probe microanalysis revealed that Nb concentration in the Nb:TiO2 films remained almost constant at 7.4 at.%, regardless of O2 flow ratio during the deposition. Resistivity of the TiO2 films was larger than 1 Ωcm while the films were deposited at 5.0 % of H2 flow ratio. In contrast, resistivity of Nb:TiO2 films exhibited 6.3×10-4 Ωcm while the films were deposited at 0.10 % of O2 flow ratio. Carrier density of the Nb:TiO2 films was 2.0×1021 cm-3, where the doping efficiency was estimated to be about 90%. All the annealed films possessed transmittance of over 60-80% in the visible region of light. Furthermore, transmittance of the Nb:TiO2 films in the near infrared region decreased due to the shift of the plasma wavelength to smaller wavelength side with the increase in the carrier density caused by Nb doping. This work was partially supported by a High-Tech Research Center project for private universities with a matching fund subsidy from the Ministry of Education, Culture, Sports, Science, and Technology (MEXIT) of Japan.
[1] Y. Furubayashi et al., Appl. Phys. Lett. 86 (2005) 252101.
[2] Y. Sato, Y. Shigesato et al., Thin Solid Films 516 (2008) 5758.