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Fabrication, characterisation and modelling of rare-earth doped alumina (Al2O3) thin films for optoelectronics

Chryssou, Costas; (1998) Fabrication, characterisation and modelling of rare-earth doped alumina (Al2O3) thin films for optoelectronics. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

The experimental aim of the work presented in this thesis was to determine the suitability of aluminium oxide (Al2O3) as host for rare-earth ions in the production of optically active thin films for optoelectronics. Two fabrication techniques were used to prepare rare-earth doped Al2O3 thin films; plasma- enhanced chemical vapour deposition (PECVD) and ion implantation. Two Al PECVD precursors were used; trimethyl-aluminium (TMA) and trimethyl-amine alane (TMAA). A number of Al2O3 thin films were deposited by PECVD on silicon and on silica glass. The thin films were analysed in terms of refractive index, thickness, chemical composition, structure and surface roughness; the optimum deposition conditions were determined. Er3+ -doped Al2O3 thin films were deposited by PECVD using both TMA and TMAA. Er doping of the alumina matrix was achieved using an organic Er precursor; Er(thd)3. Er3+ -doped Al2O3 thin films exhibited broad room-temperature photoluminescence (PL) at 1.533)m and l/e fluorescence lifetime of 2ms. The Er3+ concentration ranged from 0.01 At% to 0.2At%. The alumina matrix was co-doped with both erbium and ytterbium by ion implantation. Both Al2O3 PECVD-synthesised thin films and sapphire crystals were used as substrates. Er3+/Yb3+ co-implanted alumina films exhibited very broad room- temperature PL at 1.53m. The Er3+ and Yb3+ concentrations ranged from 0.3At% to 0.8At% and from 2.4At% to 8At% respectively. The l/e fluorescence lifetime was measured 4.2ms. Both the PL peak intensity and the fluorescence lifetime were studied as a function of the annealing temperature. Evidence for the existence of energy exchange between Er3+ and Yb3+ has been observed. Er3+ -doped Al2O3 optical waveguides were modelled using a finite element method and a Runge-Kutta algorithm. Modelling was used to predict the signal gain and was based on experimental data acquired from the PECVD-grown Er3+ -doped Al2O3 thin films. The analysis showed that Er3+ -doped Al2O3 optical waveguides exhibit improved gain characteristics compared to Er3+ -doped SiO2 optical waveguides.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Fabrication, characterisation and modelling of rare-earth doped alumina (Al2O3) thin films for optoelectronics
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
Keywords: Applied sciences; Optoelectronics
URI: https://discovery.ucl.ac.uk/id/eprint/10102601
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