Infrared absorption of hydrogen-related defects in strontium titanate

Hydrogen has a significant impact on the structural and electronic properties of metals, insulators, and semiconductors. Despite the prevalence of hydrogen, little is known about its behavior in oxides such as strontium titanate (SrTiO3). In this work, hydrogen-related defects in SrTiO3 were investigated using infrared absorption spectroscopy. Two local vibrational modes (LVMs) are observed at 3355 and 3384 cm 1 after hydrogenation at 800 C. Isotope substitution experiments revealed that the defect consists of two hydrogen atoms bound to host oxygen atoms. From the temperature dependence of the LVMs, we ascribe the complex to a strontium vacancy passivated by two hydrogen atoms. The thermal stability of the defect was determined through a series of isochronal annealing experiments on the hydrogenated SrTiO3 sample. These measurements provided evidence of “hidden hydrogen,” possibly H2 molecules, in the crystal. VC 2011 American Institute of Physics. [doi:10.1063/1.3561867]