Ion-implantation treatment (Ba, Sr)TiO₃ thin films

The effects of ion-implantation on the properties of spin-on sol-gel (Ba, Sr),TiO₃ (BST) thin films were studied by implanting with Ar⁺, N⁺ and F⁺ doses. The F⁺ implanted BST samples present better electrical and dielectric properties than the Ar⁺ or N⁺ implanted BST do. The pronounced thickness shrinkage was observed in BST films after the F⁺ implantation (before annealing treatment) and a respective increase in the refractive index was measured. After the implanted samples are annealed, the changes of thickness and refractive index depend on the concentration of the implanted dose. If the F⁺ implanted dose is low (∼5 × 10¹⁴ cm^-2), the BST preserves the densification properties. Its refractive index increases to 2.23 and it also presents a high dielectric constant of about 520. If the F⁺ implanted dose is high (≥∼1 × 10¹⁵ cm^-2), excess F⁺ ions form Sr or Ba bondings with F⁺. This will degrade the material, electric and dielectric properties. The corresponding dielectric constant is about 440. An infrared transmission study of the samples suggests that the ion-implanted sample with lower doses have fewer -OH contaminants than the non-implanted or implanted samples with high doses. Based on the results presented, it was concluded that suitable ion-implantation densifies the spin-on sol-gel BST films and reduces the -OH contaminants in the films.