Laser-induced-impurity colloid formation and dissociation in MgO single crystals

Journal Article · Tue Sep 01 04:00:00 EDT 1998 · Physical Review, B: Condensed Matter

DOI:https://doi.org/10.1103/PhysRevB.58.5236· OSTI ID:641658

Vergara, I; Gonzalez, R; Ramirez, R; Munoz Santiuste, J E ^[1]; Chen, Y ^[2]

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1. Departamento de Fisica, Escuela Politecnica Superior, Universidad Carlos III de Madrid, Butarque 15, Leganes E-28911, Madrid (Spain)
2. U.S. Department of Energy, ER 131 Division of Materials Sciences, Washington, D.C. 20874-1290 (United States)

Optical-absorption measurements were used to monitor impurity precipitation and dissociation of precipitates in both laser-irradiated and furnace-annealed MgO single crystals doped with Li, Co, or Ni impurities. In as-grown MgO:Li crystals, both Li{sub 2}O precipitates and isolated substitutional Li{sup +} ions are present; oxidation above 1100 K disperses lithium ions from the precipitates and forms stable [Li]{sup 0} centers (substitutional Li{sup +} ions, each with a trapped hole) around the precipitates. Laser-induced experiments showed that both lithium precipitation and dispersion were enhanced by the presence of cracks in the samples. A cross-section value of 0.2 bs was obtained for Li displacement, indicating that the diffusion of lithium occurs via a thermal process rather than a radiation-induced diffusion, as in the case of ionizing radiation. In MgO:Co crystals, metallic colloids were produced by thermochemical reduction at high temperatures that resulted in an extinction band at 3.7 eV due to Mie scattering from the precipitates. Dissociation of cobalt precipitates was produced under laser irradiation. An activation energy of 3.0 eV and a cross section of 0.01 bthinsps was obtained for displacement of cobalt ions from the precipitates. Laser-induced desorption and ablation was observed when the laser was focused on the crystal. In nickel-doped MgO crystals, an activation energy of 1.9 eV was determined for displacement of Ni ions from the metallic nickel precipitates. In such crystals, different patterns can be inscribed with the laser. {copyright} {ital 1998} {ital The American Physical Society}

• OSTI ID: 641658
• Journal Information: Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 9 Vol. 58; ISSN 0163-1829; ISSN PRBMDO
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ABSORPTION SPECTRA
ACTIVATION ENERGY
COBALT
COBALT IONS
COLLOIDS
DISSOCIATION
IMPURITIES
LASER RADIATION
LITHIUM
LITHIUM IONS
MAGNESIUM COMPOUNDS
MAGNESIUM OXIDES
NICKEL
NICKEL IONS
OPACITY
PRECIPITATION
VISIBLE SPECTRA