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Abstract: The 0–1.5 mol% Er3+-doped Al2O3 films have been prepared on the thermally oxidized SiO2/Si(100) substrate in the dip-coating process by the sol–gel method, using the aluminium isopropoxide [Al(OC3H7)3]-derived γ-AlOOH sols with the addition of erbium nitrate [Er(NO3)3·5H2O]. The continuous Er3+-doped Al2O3 films with the thickness of about 1.2 μm were obtained for nine coating cycles at a sintering temperature of 900 °C. The aggregate size for the Er3+-doped Al2O3 films increased with increasing the Er3+ doping concentration from 0 to 1.5 mol%. The root-mean-square roughness of the films was independent on the Er3+ doping, which was about 1.8 nm for the 0–1.5 mol% Er3+-doped Al2O3 films. The γ-Al2O3 phase with a (110) preferred orientation was produced for the Al2O3 film. The photoluminescence (PL) spectra of 0.1–1.5 mol% Er3+-doped Al2O3 films were observed at the measurement temperature of 10 K. There was no significant change for the PL peak intensity with the increase of Er3+ doping concentration from 0.1 to 1.5 mol%, and similar full width at half maximum of about 40 nm was detected for the 0.1–1.5 mol% Er3+-doped Al2O3 thin films. The Er3+-doped Al2O3 films possess the available PL properties for use in planar optical waveguides. [Copyright &y& Elsevier]

Abstract: 1 mol%Er3+–10 mol%Yb3+ codoped Al2O3 thin films have been prepared on thermally oxidized SiO2/Si(110) substrates by a dip-coating process in the non-aqueous sol–gel method from the hydrolysis of aluminum isopropoxide [Al(OC3H7)3] under isopropanol environment. Addition of N,N-dimethylformamide (DMF) as a drying control chemical additive (DCCA) into the sol suppresses formation of the cracks in the Er3+–Yb3+ codoped Al2O3 thin films when the rare-earth ion is doped with a high doping concentration. Homogeneous, smooth and crack-free Er3+–Yb3+ codoped Al2O3 thin films form at the conditions by a molar ratio of 1:1 for DMF:Al(OC3H7)3. A strong photoluminescence spectrum with a broadband extending from 1.400 to 1.700 µm centered at 1.533 µm is obtained for the Er3+–Yb3+ codoped Al2O3 thin films, which is unrelated to the addition of DMF. Controllable formation of the Er3+–Yb3+ codoped Al2O3 thin films may be explained by the fact that the DMF assisted the deprotonation process of ;OH at the surfaces of gel particles, resulting in enhancement of the degree of polymerization of sols and improvement of the mechanical properties of gel thin films. [Copyright &y& Elsevier]