Spectroscopy of Light Sensitive Defect/Impurity Centers in Photorefractive BaTio sub 3,
Abstract
Control and optimization of the behavior of photorefractive crystals requires first, a thorough understanding of the nature (charge state, local symmetry, and electronic structure) of the defects/impurities present in these materials, and of their interaction with light. Toward this end, we have carried out electron paramagnetic resonance (EPR), photo-EPR, and optical absorption measurements on a variety of BaTiO3 samples doped with transition metal ions. These crystals were grown by top-seeded solution growth from a melt with an excess of titanium oxides. In order to identify the charge states of transition metal dopants and to correlate them with the processing conditions (annealing in oxidizing and reducing atmospheres), we have carried out extensive EPR measurements as a function of temperature on both single crystals and polycrystalline samples. We describe in detail our EPR results on polycrystalline samples for various oxidation-reduction conditions. From these measurements we are able to establish a relative energy scale for the positions of the various charge states of the transition metal dopants in the bandgap of BaTiO3.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 22, 1992
- Accession Number
- ADP006776
Entities
People
- Barry A. Wechsler
- Robert N. Schwartz
- Ross A. Mcfarlane
Organizations
- HRL Laboratories