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Research on the defect structure and <i>g</i> factors for the tetragonal (CrO <sub/>4</sub> ) <sup>3?</sup> impurity center in ZrSiO <sub/>4</sub> : Cr <sup>5+</sup> crystal
摘要： The EPR g factors g// and g⊥ for the tetragonal (CrO4)3? impurity center in ZrSiO4: Cr5+ crystal are studied from the high-order perturbation formulas based on the two-mechanism (the crystal field and charge-transfer mechanisms) model. The studies indicate that differing from the tetragonally-elongated host (SiO4)4? tetrahedron, the dominant defect structure of the substitutional (CrO4)3? tetrahedron is tetragonally- compressed with the ground state |dz2(cid:3) due to the Jahn-Teller distortion. Furthermore, the agreement of g factors between calculation and experiment requires a small admixture of the first excited state |dx2?y2(cid:3) to the ground state |dz2(cid:3) due to the vibrational motion of ligands, which leads a compressed (CrO4)3? tetrahedron to become a twinkling elongated one, These results are discussed.
关键词： Defect structure,Cr5+,g factors,dynamic effect,ZrSiO4
更新于2025-09-23 15:21:01
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Investigations of the electron paramagnetic resonance parameters and defect structures for Cu2+ ions in BeO crystal with trigonally distorted tetrahedral symmetry
摘要： The electron paramagnetic resonance(EPR) parameters (g factors gi and hyperfine structure constants Ai, where i=x, z) for Cu2+ ions embedded in beryllium oxide (BeO) crystal at Be2+ sites with C3v local symmetry have been calculated by the complete diagonalization method (CDM) and high-order perturbation theory method (PTM). The calculated results from the two methods are in reasonable agreement with the observed data available. The defect structural data of the trigonal Cu2+ center in beryllium oxide are determined from the calculations and analyses.The calculated results show that the Be2+ ions are replaced by Cu2+ ions in BeO crystal and the ligands undergo outward movement.
关键词： Electron paramagnetic resonance (EPR),Crystal - and ligand- field theory,Defect structure,BeO:Cu2+
更新于2025-09-10 09:29:36
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Asymmetry of the Defect Structure of Semipolar GaN Grown on Si(001)
摘要： The defect structure of a thick (~15 μ m) semipolar gallium nitride (GaN) layer grown by hydride–chloride vapor phase epitaxy on a Si(001) substrate with buffer layers has been studied by transmission electron microscopy. The asymmetry of the defect structure of GaN epilayer has been revealed and analyzed. The influence of this asymmetry on the rate of decrease in the density of threading dislocations in the growing epitaxial layer is discussed.
关键词： transmission electron microscopy,semipolar GaN,threading dislocations,hydride–chloride vapor phase epitaxy,defect structure
更新于2025-09-04 15:30:14