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Luminescence properties of lanthanide and ytterbium lanthanide titanate thin films grown by atomic layer deposition

Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films, ISSN: 1520-8559, Vol: 34, Issue: 1
2016
  • 9
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  • 12
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Metric Options:   Counts1 Year3 Year

Metrics Details

  • Citations
    9
    • Citation Indexes
      9
  • Captures
    12

Article Description

Lanthanide based luminescent materials are highly suitable as down conversion materials in combination with a UV-absorbing host material. The authors have used TiO as the UV-absorbing host material and investigated the energy transfer between TiO and 11 different lanthanide ions, Ln (Ln = La, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb) in thin films grown by atomic layer deposition. They have also investigated the possibility to improve the overall energy transfer from TiO to Yb with a second Ln, in order to enhance down conversion. The films were grown at a substrate temperature of 300 °C, using the Ln(thd)/O (thd = 2,2,6,6-tetramethyl-3,5-heptanedione) and TiCl/HO precursor pairs. The focus of the work is to explore the energy transfer from TiO to Ln ions, and the energy transfer between Ln and Yb ions, which could lead to efficient down conversion. The samples have been characterized by x-ray diffraction, x-ray fluorescence, spectroscopic ellipsometry, and photoluminescence. All films were amorphous as deposited, and the samples have been annealed at 600, 800, and 1000 °C in order to investigate the correlation between the crystallinity and luminescence. The lanthanum titanium oxide samples showed a weak and broad emission centered at 540 nm, which was absent in all the other samples, indicating energy transfer from TiO to Ln in all other lanthanide samples. In the amorphous phase, all samples, apart from La, Tb, and Tm, showed a typical f-f emission when excited by a 325 nm HeCd laser. None of the samples showed any luminescence after annealing at 1000 °C due to the formation of LnTiO. Samples containing Nd, Sm, and Eu show a change in emission spectrum when annealed at 800 °C compared to the as-deposited samples, indicating that the smaller lanthanides crystallize in a different manner than the larger lanthanides. Energy transfer from Ln to Yb was observed neither in the amorphous or annealed samples. On the other hand, Yb was found to be an efficient sensitizer for Ho's 1200 nm emission.

Bibliographic Details

Per Anders Hansen; Helmer Fjellvåg; Ola Nilsen; Terje G. Finstad

American Vacuum Society

Physics and Astronomy; Materials Science

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