Luminescent Properties of Multilayered Eu₂O₃ and TiO₂ Grown by Atomic Layer Deposition**

Abstract

Atomic layer deposition (ALD) is used to control the interatomic interactions of Eu and Ti in multilayered structures, as measured by characterizing the luminescent properties of the deposited material. Luminescent multilayer structures of Eu 2 O 3 and TiO 2 are deposited as thin films by ALD at 300°C using Eu(thd) 3 /O 3 and TiCl 4 /H 2 O (thd ¼ 2,2,6,6-tetramethyl-3,5-heptanedione) as precursor systems. The individual layer thickness of the multilayered structure is produced from first N ALD cycles Eu 2 O 3 and then N ALD cycles TiO 2 (N ¼ 1 to 50), while the total film thickness is kept constant. The thinnest distinct layers are detected for N ¼ 10, where each layer is measured to be less than 0.4 nm thick. The as-deposited films are smooth (root mean square (rms) roughness < 0.4 nm) and amorphous, independent of the layer thickness, N. The refractive index and extinction coefficient are also independent of N, while the luminescence efficiency is constant for N up to 10 cycles, and decreases for thicker superlayers. Annealing deteriorates the layered structures, causing a decrease in luminescence efficiency for thin superlayers, while thick superlayers increase in efficiency upon annealing. The films are characterized by spectroscopic ellipsometry (SE), photoluminescence (PL), X-ray diffraction (XRD), X-ray fluorescence (XRF), X-ray reflectivity (XRR), and atomic force microscopy (AFM).

Photon up‐converting (Yb,Er)2O3 thin films by atomic layer deposition

“…Here, it should be mentioned that the ALD technique (by that time, atomic layer epitaxy or ALE) was originally invented to meet the challenge of depositing high‐quality thin films for electroluminescence displays . Although basic thermal ALD processes have been available for most of the lanthanoid (Ln) oxides for a while , there are only a few reports on luminescent thin films fabricated by ALD or the related MLD (molecular layer deposition) technique .…”

Atomic Layer Deposition of oriented nickel titanate (NiTiO3)

“…[65,66] With the aid of post-deposition annealing to produce Fe3O4, alternating layers of Al2O3 and Fe3O4 have shown tunable microwave absorption properties. [67] The photoluminescence of Eu2O3/TiO2 stacks have been investigated with control of layer thickness down to one unit cell, [68] while Al2O3/Y2O3 multilayers have been studied for optical waveguide purposes. [69] With the flexibility ALD provides, changing between depositions of different materials is, as mentioned, easy.…”

Self-limiting adsorption of Eu3+ on the surface of rod-shape anatase TiO2 nanocrystals and post-synthetic sensitization of the europium-based emission

“…[45][46][47][48][49][50][51][52][53][54][55][56][57]61 Also, it has been shown that amorphous Eu 2 O 3 exhibits similar luminescence ( 5 D 0  7 F J transitions, relative intensities, and line-broadening) upon irradiation at 325 nm. 63,64 Nanocrystalline Eu 2 O 3 nanotubes give rise to a similar emission fingerprint when excited at 254 nm. 65 Therefore Eu-based luminescence could arise from TiO 2 excitation and energy transfer to Eu 3+ or from direct excitation of the O  Eu LMCT band.…”