Nanostructure and temperature-dependent photoluminescence of Er-doped Y2O3 thin films for micro-optoelectronic integrated circuits

Abstract

The nanostructure and photoluminescence of polycrystalline Er-doped Y2O3 thin films, deposited by radical-enhanced atomic layer deposition (ALD), were investigated in this study. The controlled distribution of erbium separated by layers of Y2O3, with erbium concentrations varied from 6to14at.%, was confirmed by elemental electron energy loss spectroscopy (EELS) mapping of Er M4 and M5. This unique feature is characteristic of the alternating radical-enhanced ALD of Y2O3 and Er2O3. The results are also consistent with the extended x-ray absorption fine structure (EXAFS) modeling of the Er distribution in the Y2O3 thin films, where the EXAFS data were best fitted to a layer-like structure. X-ray diffraction (XRD) and selected-area electron diffraction (SAED) patterns revealed a preferential film growth in the [111] direction, showing a lattice contraction with increasing Er doping concentration, likely due to Er3+ of a smaller ionic radius replacing the slightly larger Y3+. Room-temperature photoluminescence characteristic of the Er3+ intra-4f transition at 1.54μm was observed for the 500Å, 8at.% Er-doped Y2O3 thin film, showing various well-resolved Stark features due to different spectroscopic transitions from the I13∕24→I15∕24 energy manifold. The result indicates the proper substitution of Y3+ by Er3+ in the Y2O3 lattice, consistent with the EXAFS and XRD analyses. Thus, by using radical-enhanced ALD, a high concentration of optically active Er3+ ions can be incorporated in Y2O3 with controlled distribution at a low temperature, 350°C, making it possible to observe room-temperature photoluminescence for fairly thin films (∼500–900Å) without a high temperature annealing.

Plasma-Assisted Atomic Layer Deposition: Basics, Opportunities, and Challenges

“…A classic example is the ALD of metal oxides from b-diketonate precursors, such as those with acac (acetylacetonate), [97][98][99][100] hfac (1,1,1,5,5,5-hexafluoroacetylacetonate), 101,161,162 and thd (2,2,6,6,-tetramethyl-3,5-heptanedionato) 102,104,[275][276][277][278][279] ligands. Such precursors require more reactive co-reactants as they show no or low reactivity with H 2 O (in essence, they do not readily undergo hydrolysis reactions).…”

Er3+ and Si luminescence of atomic layer deposited Er-doped Al2O3 thin films on Si(100)

“…In the lateral direction, the separation between the individual dopant atoms is dictated by the growth-per-cycle, which is related, among other variables, to the steric hindrance effect of the specific precursor molecules. 17 Furthermore, the excellent conformality of ALD provides a means for coating high-aspect ratio structures, porous materials, and small particles.…”

“…In addition, ALD has been used for Er incorporation in Y 2 O 3 by alternating the growth of Y 2 O 3 and Er 2 O 3 layers. 17,27 In this study, we used thermal ALD to synthesize amorphous Al 2 O 3 :Er films on Si wafers. The focus of the paper is the relation between the (structural) changes of the material during annealing and the optical activation of Er 3þ .…”

Nanoparticle characterization of Er-doped SnO2 pellets obtained with different pH of colloidal suspension

“…32,33 This low solubility is related, mainly, to the difference between ionic radius of Eu 3þ (0.95Å ) and Sn þ4 (0.76Å ). 34 On the other hand, Er 3þ has ionic radius of 0.89Å , 35 and then, it is believed that Er 3þ presents similar solubility (0.05 at. %) in the SnO 2 matrix, where the excess segregates to the grain boundary layer.…”