Observation of Blue-Light Emission Band from Eu-Doped Ta₂O₅ Thin Films Prepared Using Co-Sputtering

Kenta Miura^*, Yuki Arai, Osamu Hanaizumi

Graduate School of Science and Technology, Gunma University, Kiryu, Japan.

DOI: 10.4236/msa.2015.67069                

Abstract

In this paper, we report on the first observation of blue-light emission bands from europium-doped tantalum pentoxide (Ta₂O₅:Eu) thin films prepared using a simple co-sputtering method. We prepared four specimens from one as-deposited sample, and we subsequently annealed them at 700°C, 800°C, 900°C, or 1000°C for 20 min. Four remarkable photoluminescence (PL) peaks at wavelengths of 600, 620, 650, and 700 nm due to the ⁵D₀→⁷F₁, ⁵D₀→⁷F₂, ⁵D₀→⁷F₃, and ⁵D₀→⁷F₄ transitions of Eu³⁺ were observed from all the specimens, and blue PL peaks around a wavelength of 450 nm were also observed from the specimens annealed at 800°C, 900°C, and 1000°C. The blue PL peaks seem to be originated from the 4f⁶5d¹→4f⁷ transition of Eu²⁺. Both Eu³⁺ and Eu²⁺ ions seem to exist in our Ta₂O₅:Eu co-sputtered thin films annealed at temperatures from 800°C to 1000°C. Such Ta₂O₅:Eu co-sputtered thin films seem to be used as multi-functional coating films having both anti-reflection and down-conversion effects for realizing high-efficiency silicon solar cells.

Keywords

Ta₂O₅ , Eu, Co-Sputtering, Blue-Light Emission Band

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	Hanaizumi, O., Miura, K., Saito, M., Sato, T., Kawakami, S., Kuramochi, E. and Oku, S. (2000) Frontiers Related with Automatic Shaping of Photonic Crystals. IEICE Transactions on Electronics, E83-C, 912-919.
[2]	Sato, T., Miura, K., Ishino, N., Ohtera, Y., Tamamura, T. and Kawakami, S. (2002) Photonic Crystals for the Visible Range Fabricated by Autocloning Technique and Their Application. Optical and Quantum Electronics, 34, 63-70. http://dx.doi.org/10.1023/A:1013382711983
[3]	Cid, M., Stem, N., Brunetti, C., Beloto, A.F. and Ramos, C.A.S. (1998) Improvements in Anti-Reflection Coatings for High-Efficiency Silicon Solar Cells. Surface and Coatings Technology, 106, 117-120. http://dx.doi.org/10.1016/S0257-8972(98)00499-X
[4]	Zhu, M., Zhang, Z. and Miao, W. (2006) Intense Photoluminescence from Amorphous Tantalum Oxide Films. Applied Physics Letters, 89, Article ID: 021915. http://dx.doi.org/10.1063/1.2219991
[5]	Miura, K., Miyazaki, H. and Hanaizumi, O. (2008) Observation of Blue-Light Emission from Tantalum Oxide Films Deposited by Radio-Frequency Magnetron Sputtering. IEICE Transactions on Electronics, E91-C, 1669-1672. http://dx.doi.org/10.1093/ietele/e91-c.10.1669
[6]	Sanada, T., Wakai, Y., Nakashita, H., Matsumoto, T., Yogi, C., Ikeda, S., Wada, N. and Kojima, K. (2010) Preparation of Eu3+-Doped Ta2O5 Phosphor Particles by Sol-Gel Method. Optical Materials, 33, 164-169. http://dx.doi.org/10.1016/j.optmat.2010.08.018
[7]	Singh, M.K., Fusegi, G., Kano, K., Bange, J.P., Miura, K. and Hanaizumi, O. (2009) Intense Photoluminescence from Erbium-Doped Tantalum Oxide Thin Films Deposited by Sputtering. IEICE Electronics Express, 6, 1676-1682. http://dx.doi.org/10.1587/elex.6.1676
[8]	Singh, M.K., Miura, K., Fusegi, G., Kano, K. and Hanaizumi, O. (2013) Visible-Light Emission Properties of Erbium-Doped Tantalum-Oxide Films Produced by Co-Sputtering. Key Engineering Materials, 534, 154-157. http://dx.doi.org/10.4028/www.scientific.net/KEM.534.154
[9]	Miura, K., Osawa, T., Suzuki, T., Yokota, Y. and Hanaizumi, O. (2015) Fabrication and Evaluation of Green-Light Emitting Ta2O5:Er, Ce Co-Sputtered Thin Films. Results in Physics, 5, 78-79. http://dx.doi.org/10.1016/j.rinp.2015.02.002
[10]	Miura, K., Arai, Y., Kano, K. and Hanaizumi, O. (2015) Fabrication of Erbium and Ytterbium Co-Doped Tantalum-Oxide Thin Films Using Radio-Frequency Co-Sputtering. Materials Sciences and Applications, 6, 343-347. http://dx.doi.org/10.4236/msa.2015.65039
[11]	Miura, K., Osawa, T., Suzuki, T., Yokota, Y. and Hanaizumi, O. (2015) Yellow Light Emission from Ta2O5:Er, Eu, Ce Thin Films Deposited Using a Simple Co-Sputtering Method. Results in Physics, 5, 26-27. http://dx.doi.org/10.1016/j.rinp.2014.11.003
[12]	Miura, K., Osawa, T., Yokota, Y., Suzuki, T. and Hanaizumi, O. (2014) Fabrication of Tm-Doped Ta2O5 Thin Films Using a Co-Sputtering Method. Results in Physics, 4, 148-149. http://dx.doi.org/10.1016/j.rinp.2014.08.011
[13]	Miura, K., Osawa, T., Yokota, Y., Suzuki, T. and Hanaizumi, O. (2015) Photoluminescence Properties of Thulium and Cerium Co-Doped Tantalum-Oxide Films Prepared by Radio-Frequency Co-Sputtering. Materials Sciences and Applications, 6, 263-268. http://dx.doi.org/10.4236/msa.2015.64031
[14]	Miura, K., Osawa, T., Yokota, Y. and Hanaizumi, O. (2014) Fabrication and Evaluation of Ta2O5:Y2O3 Co-Sputtered Thin Films. Results in Physics, 4, 185-186. http://dx.doi.org/10.1016/j.rinp.2014.09.004
[15]	Miura, K., Kano, K., Arai, Y. and Hanaizumi, O. (2015) Preparation of Light-Emitting Ytterbium-Doped Tantalum-Oxide Thin Films Using a Simple Co-Sputtering Method. Materials Sciences and Applications, 6, 209-213. http://dx.doi.org/10.4236/msa.2015.62024
[16]	Rodriguez, V.D., Tikhomirov, V.K., Mendez-Ramos, J., Yanes, A.C. and Moshchalkov, V.V. (2010) Towards Broad Range and Highly Efficient Down-Conversion of Solar Spectrum by Er3+-Yb3+ Co-Doped Nano-Structured Glass-Ceramics. Solar Energy Materials and Solar Cells, 94, 1612-1617. http://dx.doi.org/10.1016/j.solmat.2010.04.081
[17]	Aarts, L., van der Ende, B.M. and Meijerink, A. (2009) Downconversion for Solar Cells in NaYF4:Er, Yb. Journal of Applied Physics, 106, Article ID: 023522. http://dx.doi.org/10.1063/1.3177257
[18]	Ueda, J. and Tanabe, S. (2011) Broadband near Ultra Violet Sensitization of 1 μm Luminescence in Yb3+-Doped CeO2 Crystal. Journal of Applied Physics, 110, Article ID: 073104. http://dx.doi.org/10.1063/1.3642984
[19]	Miura, K., Arai, Y., Osawa, T. and Hanaizumi, O. (2012) Light-Emission Properties of Europium-Doped Tantalum-Oxide Thin Films Deposited by Radio-Frequency Magnetron Sputtering. Journal of Light & Visual Environment, 36, 64-67. http://dx.doi.org/10.2150/jlve.36.64
[20]	Osawa, T. (2014) Fabrication and Evaluation of Functional-Material-Doped Tantalum-Oxide Thin Films. Master’s Thesis, Gunma University, Maebashi. (In Japanese)
[21]	Ren, L.J., Lei, X.H., Du, X.Q., Jin, L., Chen, W.M. and Feng, Y.A. (2013) Effect of Eu2O3 Concentration on Luminescent Properties of Ce/Tb/Eu Co-Doped Calcium Borosilicate Glass for White LED. Journal of Luminescence, 142, 150-154. http://dx.doi.org/10.1016/j.jlumin.2013.04.006
[22]	Bange, J.P., Singh, M.K., Kano, K., Miura, K. and Hanaizumi, O. (2011) Structural Analysis of RF Sputtered Er Doped Ta2O5 Films. Key Engineering Materials, 459, 32-37. http://dx.doi.org/10.4028/www.scientific.net/KEM.459.32