Preparation and photoluminescence of Er3+-doped Al2O3 films by sol-gel method

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.