a b s t r a c tThulium-doped tantalum-oxide (Ta 2 O 5 :Tm) thin films were prepared using a simple co-sputtering method. A remarkable photoluminescence peak having a wavelength of around 800 nm due to Tm 3+ was observed from a film annealed at 900°C for 20 min. The d-Ta 2 O 5 (hexagonal) phase of the Ta 2 O 5 :Tm sputtered film is very important for obtaining strong photoluminescence.

Light-emitting europium-doped tantalum-oxide thin films were prepared by radio-frequency magnetron sputtering. Red photoluminescence was obtained from the films after annealing by ultraviolet-laser excitation. Four peaks having wavelengths of around 600, 620, 650, and 700 nm were observed from films annealed at 600 to 900 C. The strongest intensity of the most remarkable 620-nm peak was obtained from the film annealed at 700 C for 20 min.

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We prepared CuO-Ta2O5 composite films using our simple co-sputtering method for the first time. Four specimens were prepared from an as-deposited CuO-Ta2O5 sample by cutting it using a diamond-wire saw, and the specimens were subsequently annealed at 600˚C-900˚C. The X-ray diffraction and photoluminescence (PL) of the annealed specimens were evaluated. The CuO-Ta2O5 film annealed at 600˚C seemed to be primarily amorphous phase, and a sharp PL peak at a wavelength of 450 nm, due to the existence of Cu 2+ , was observed from the film. In contrast, the CuO-Ta2O5 films annealed at 700˚C, 800˚C, and 900˚C seemed to be tetragonal CuTa2O6 phases. We expect that good-quality CuTa2O6 films can be obtained using our very simple co-sputtering method and subsequent annealing above 900˚C. Such CuTa2O6 films can be used in chemisorptions conductometric gas sensors.

a b s t r a c tErbium and cerium co-doped tantalum-oxide (Ta 2 O 5 :Er, Ce) thin films were fabricated using radio-frequency co-sputtering of Ta 2 O 5 , Er 2 O 3 , and CeO 2 for the first time. Enhanced green-light emission due to Er 3+ that seems to be sensitized by Ce 3+ was observed from the film annealed at 900°C for 20 min. From XRD measurements of the films, the b-Ta 2 O 5 (orthorhombic), d-Ta 2 O 5 (hexagonal), and (2 0 1) Ta 2 O 5 phases seem to be very important for obtaining green PL from them. Such Ta 2 O 5 :Er, Ce co-sputtered films can be used as high-refractive-index materials of autocloned photonic crystals that can be applied to novel green-light-emitting devices, and they will also be used as multi-functional coating films that can work both as anti-reflection and down-conversion films for realizing high-efficiency silicon solar cells.