Observation of Blue-Light Emission Band from Eu-Doped Ta₂O₅Thin Films Prepared Using Co-Sputtering

Abstract

In this paper, we report on the first observation of blue-light emission bands from europium-doped tantalum pentoxide (Ta 2 O 5 :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 &deg C, 800 &deg C, 900 &deg C, or 1000 &deg C for 20 min. Four remarkable photoluminescence (PL) peaks at wavelengths of 600, 620, 650, and 700 nm due to the 5 D 0 → 7 F 1 , 5 D 0 → 7 F 2 , 5 D 0 → 7 F 3 , and 5 D 0 → 7 F 4 transitions of Eu 3+ 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 &deg C, 900 &deg C, and 1000 &deg C. The blue PL peaks seem to be originated from the 4f 6 5d 1 →4f 7 transition of Eu 2+ . Both Eu 3+ and Eu 2+ ions seem to exist in our Ta 2 O 5 :Eu co-sputtered thin films annealed at temperatures from 800 &deg C to 1000 &deg C. Such Ta 2 O 5 :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.