Surface chemical composition and optical properties of nitrogen-doped Ba0.6Sr0.4TiO3 thin films

The effect of nitrogen (N) doping on surface chemical composition and optical properties of Ba0.6Sr0.4TiO3 (BST) thin films have been investigated using x-ray photoemission spectroscopy (XPS) and transmittance measurement. It was found that the nitrogen doping induced Ti3+∕4+ states and formed Ti–N bonds in BST films. With lower implantation energy, the oxygen vacancies can be effectively eliminated because of N dopants substitution. Unfortunately, the oxygen vacancies possibly increased when enhance implantation energy. In addition, the N-doped BST films indicated larger amount of perovskite phase and lower content additional phase at surface. The chemical shifts in XPS confirmed the forming of Ba–N and Sr–N bonds in N-doped BST films. The optical properties for as-grown and N-doped BST films were considered at wavelength range from 190to1100nm. The optical constants, including refractive index n and extinction coefficient k, were calculated by fitting transmittance spectra with single Tauc-Lorenz and Lo...