Optical Spectroscopy of Eu³⁺ Doped ZnO Nanocrystals

Abstract

The energy levels and local structures of Eu 3+ incorporated in the lattice and surface sites of ZnO nanocrystals were investigated based on the high-resolution fluorescence spectra at 10 K. Radiative emissions from 5 D 1 were first observed for Eu 3+ at the lattice site of ZnO. It is shown that the site symmetry of Eu 3+ at the lattice site descends from C 3V to C s or C 1 , whereas Eu 3+ ions at the surface occupy more disordered sites of the lowest symmetry C 1 . The luminescence decay of 5 D 0 at the lattice site, showing a rise time and longer lifetime, behaves distinctly from that of the surface sites. Because of a small filling factor (52%) of nanoparticles, the 5 D 0 lifetime of Eu 3+ is significantly affected by the surrounding medium, which can be well interpreted with the virtual-cavity model. The Judd-Ofelt intensity parameters of Eu 3+ in ZnO nanocrystals were determined, with Ω 2,4,6 values of (9. 59, 8.11, <0.25) and (21.51, 2.30, <0.25) in units of 10 -20 cm 2 for Eu 3+ at the surface and lattice sites, respectively. A defect-mediated energy transfer from the ZnO band gap to Eu 3+ was observed. The growth mechanism for the incorporation of Eu 3+ into the ZnO lattice was also revealed.

Synthesis and characterization of Eu3+, Ti4+@ ZnO organosols and nanocrystalline c-ZnTiO3thin films aiming at high transparency and luminescence

“…As observed previously [10], the majority of these films do not show sharp PL lines characteristic of Eu 3+ in a bulk crystal, reflecting the presence of europium in an amorphous phase or in nanocrystals with the size below 10 nm [32]. The c-ZnTiO 3 nanocrystal growth could be hindered with the increasing Eu 3+ content, likely due to the destabilizing effect of Eu 3+ ions on the surface of a nanocrystal as reported for ZnO or TiO 2 nanocrystals [33,34]. Moreover, Eu 3+ ions could be located not only in the bulk but also at the surface lattice sites of the ZnO materials [32].…”

“…The decay of the gel is faster, with the corresponding lifetimes of 0.57 and 1.04 ms. In ZnO nanocrystal, the corresponding lifetimes were 0.69 and 1.05 ms [33]. The multiexponential decay reveals that at least two kinds of Eu 3+ centers coexist in the Ti@ZnO gel and powder.…”

Surfactant Assisted Sonochemical Synthesis and Characterization of Gadolinium Doped Zinc Oxide Nanoparticles

“…)-doped ZnO have been reported. [24][25][26][27][28][29][30][31] Lanthanide ions are considered as excellent candidates as dopant of the ZnO due to their many optical and magnetic advantages. Gd is recognized as a potential dopant and has become the focus of numerous investigations because of its promising applications in optoelectronic and magnetic devices.…”

Silicon‐Modified Rare‐Earth Transitions—A New Route to Near‐ and Mid‐IR Photonics

“…Figure 2 shows a comparison of the PL spectrum of Eu in silicon with a Eu spectrum from a zinc oxide host. [ 30 ] The upper plot shows PL data in the 5500-8000 cm −1 range measured at 20 K and at 80 K from silicon samples coimplanted with B and Eu (Si:B&Eu). The lower plot shows the usual Eu 3+ PL spectrum in the visible (14700-17200 cm −1 ), in this case in a ZnO host abstracted from ref.…”

“…Light emission in several larger band gap semiconductors and other hosts incorporating Eu 3+ , Yb 3+ , and Ce 3+ has been previously reported. [28][29][30][31][32][33] PL at low temperatures was the main technique used to optically characterize these materials. Luminescence due to their well-known RE internal transitions is observed at ≈615 nm for Eu, 980 nm for Yb, and in the UV/ blue (300-400 nm) for Ce.…”