Fabrication and photoluminescence of Er ₃₊-doped Al ₂O ₃ thin films with sol-gel method

Erbium doped Al ₂O ₃ thin films were fabricated on quartz substrates in dip-coating process by sol-gel method, using the aluminum isopropoxide [Al(OC ₃H ₇) ₃]-derived AlOOH sols with the addition of erbium nitrate [Er(NO ₃) ₃ ·5H ₂O]. The as-deposited films, which erbium concentration was between 20 and 43 mol%, were annealed in air from 600 to 1200 °C. The phase structure was detected by X-ray diffraction (XRD) and the PL spectra in the wavelength range of 1400-1700 nm were investigated by spectrophotometer, which was exited by a 760 nm semiconductor LD. The PL spectrum shows a broadband extending from 1.430 to 1.670 μm and centered at 1.55 μm, corresponding to the intra-4f transition between the first excited (4I _13/2) and the ground state (4I _15/2) of Er ³⁺. The full width at half maximum (FWHM) of PL peaks increase from 60 to 100 nm with temperature increased from 600 to 1200 °C.