Surface Eu-Treated ZnO Nanowires with Efficient Red Emission

The structural and optical properties of post surface Eu-treated ZnO nanowires (NWs) have been investigated systematically. It is found that the Eu 3+ ions are in the Eu 2 O 3 -like state located at the surface of ZnO NWs. Sharp intense red emissions in the range of 580−650 nm due to the intra-4 f transition of Eu 3+ ions are observed from the sample. The temperature-dependent photoluminescence (PL) measurement shows that the intensity of the Eu 3+ ions emission is related to the near-band-edge (NBE) emission of ZnO NWs, indicating direct energy transfer from ZnO to Eu 3+ ions. Finally, the time-resolved PL measurement was carried out, and the roles played by the Eu 2 O 3 -like layers are discussed in detail. It is found that the Eu 2 O 3 layers not only suppress the deep level emission (DLE) in ZnO NWs but also provide efficient energy trap centers supporting the direct energy transfer from ZnO to Eu 3+ ions.