Lattice strain dependent optical transitions in Ho3+-ion doped barium strontium titanate thin films

The influence of lattice strain on the strength of dipoles in the Ho 3+ -doped barium-strontium titanate (BST) thin films has been analyzed. Thin films were produced by using the sol–gel technique on Si substrate. The resulting stress due to fabrication process was quantified by analyzing the {200} planes of the cubic perovskite structure and comparing them with the data for bulk materials. The influence of strain and changes due to Ho 3+ -ion doping were characterized by Raman and visible photoluminescence spectroscopy, which clearly show the evidence for the increased tetragonality due to weaker dipole interaction at B-sites of cubic perovskite in the presence of Ho 3+ -ions at concentrations larger than 3 mol%. The film strain can therefore be controlled to enhance the intensity of emitted light at 650 nm.