Infrared characterization of strontium titanate thin films

• Published in: Applied surface science 2004-11, Vol.238 (1-4), p.395-399
• Main Authors: Almeida, B.G., Pietka, A., Mendes, J.A.
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Infrared and Raman spectra; Infrared and raman spectra and scattering; Infrared spectroscopy; Modeling; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Physics; Strontium titanate; Structure and morphology; thickness; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Thin film structure and morphology
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2004.05.260

Strontium titanate thin films have been prepared at different oxygen pressures with various post-deposition annealing treatments. The films were deposited by pulsed laser ablation at room temperature on Si(001) substrates with a silica buffer layer. Infrared reflectance measurements were performed in order to determine relevant film parameters such as layer thicknesses and chemical composition. The infrared reflectance spectra were fitted by using adequate dielectric function forms for each layer. The fitting procedure provided the extraction of the dielectric functions of the strontium titanate film, the silica layer and the substrate. The as-deposited films are found to be amorphous, and their infrared spectra present peaks corresponding to modes with high damping constants. As the annealing time and temperature increases the strontium titanate layer becomes more ordered so that it can be described by its SrTiO3 bulk mode parameters. Also, the silica layer grows along with the ordering of the strontium titanate film, due to oxidation during annealing.