Photoluminescence properties of Eu-doped ZnO films grown by sputtering-assisted metalorganic chemical vapor deposition

Photoluminescence (PL) properties of Eu-doped ZnO (ZnO:Eu) grown by a sputtering-assisted metalorganic chemical vapor deposition technique were investigated. In PL measurements at 300 K, the samples annealed at 600 °C for 30 min showed clear red-emission lines due to the intra-4f shell transition of 5D0→7FJ (J=0–4) in Eu3+. In photoluminescence excitation (PLE) spectra, the PL was observed under the high-energy excitation above the band-gap energy of ZnO (indirect excitation) and the low-energy excitation resonant to the energy levels of 7F0–5D3 and 7F0–5D2 transitions in Eu3+ (direct excitation). The PL lifetime under the indirect excitation was shorter than that under the direct excitations. These PL properties revealed that the energy transfer from ZnO host to Eu3+ was accompanied under indirect excitation.