Accession Number : ADP006776

Title :   Spectroscopy of Light Sensitive Defect/Impurity Centers in Photorefractive BaTio sub 3,

Corporate Author : HUGHES RESEARCH LABS MALIBU CA

Personal Author(s) : Schwartz, Robert N. ; Wechsler, Barry A. ; McFarlane, Ross A.

Report Date : 22 MAY 1992

Pagination or Media Count : 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.

Descriptors :   *CRYSTAL DEFECTS, ABSORPTION, BEHAVIOR, CONTROL, CRYSTALS, ELECTRONICS, ELECTRONS, ENERGY, FUNCTIONS, IMPURITIES, INTERACTIONS, IONS, MATERIALS, MEASUREMENT, MELTS, METALS, OPTIMIZATION, OXIDATION, POLYCRYSTALLINE, PROCESSING, REDUCTION, SCALE, SINGLE CRYSTALS, SYMMETRY, TEMPERATURE, TRANSITION METALS, TRANSITIONS, BARIUM TITANATES, RESONANCE, CRYSTAL GROWTH, REFRACTION.

Subject Categories : Optics
      Crystallography

Distribution Statement : APPROVED FOR PUBLIC RELEASE