Effect of Lattice Mismatch Strain in Oxygen Deficient Strontium Titanate Films*

SrTiO₃ (STO) is a quantum paraelectric material which exhibits electronic phenomena that are interesting for technological applications. Applications of STO include its use as a dielectric layer in semiconductor devices, and as a photocatalytic material. Varying the oxygen content in STO affects the crystal structure and electronic properties which are important for such applications. In oxygen deficient STO (SrTiO_3-y)_, the valence of the titanium ion and the average ionic sizes are different from those of the stoichiometric form (SrTiO₃), leading to structural and electronic changes. Our study focuses on the structure and electronic properties of oxygen deficient epitaxial thin films of STO grown by Pulsed Laser Deposition on substrates with varying degrees of lattice mismatch. Previous work in our laboratory has shown that tensile strain promotes oxygen deficiency in epitaxial thin films of another perovskite oxide CaMnO3-y. Such coupling may be employed to engineer novel phases in thin films. We explore whether a similar coupling between strain and oxygen stoichiometry is present in STO. We will present the results of x-ray diffraction, electrical conductivity, Raman spectroscopy and atomic force microscopy studies.