Effect of Er substituting sites on upconversion luminescence of Er3+-doped BaTiO3 films

Erbium-doped BaTiO3 films on LaNiO3/Si substrates were fabricated by sol-gel method. The crystalline structure, morphologies and upconversion (UC) luminescence properties of films were respectively investigated by X-ray diffraction (XRD), atomic force microcopy (AFM) and photoluminescence (PL). The results indicate that both of the microstructure and luminescence are found to be dependent on Er3+ substituting sites. The samples with A-site substitution have smaller lattice constants, larger grains and smoother surface than those with B-site substitution. The photoluminescence spectra show that both of the samples have two stronger green emission bands centered at 528 and 548 nm and a weak red emission band centered at 673 nm, which correspond to the relaxation of Er3+ from H-2(11/2), S-4(3/2), and F-4(9/2) levels to the ground level I-4(15/2), respectively. Compared with B-site doped films, A-site doped films have a stronger integrated intensity of green emissions and a weaker relative intensity of red emissions. The differences could be explained by the crystalline quality and cross relaxation (CR) process.