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  • American Institute of Physics (AIP)  (6)
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  • 1
    Electronic Resource
    Electronic Resource
    Identification of point defects in hydrothermally grown KTiOPO4 (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 2991-2994 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electron paramagnetic resonance has been used to investigate radiation-induced point defects in hydrothermally grown single crystals of potassium titanyl phosphate ( KTiOPO4 or KTP). The crystals were irradiated at 77 K with 60–kV x rays. A trapped-hole center, a Ti3+ center, and a Pt3+ center were observed between 10 and 30 K after the initial 77-K irradiation. These defects become thermally unstable near 160 K. The trapped hole is localized on an oxygen ion adjacent to a potassium vacancy and has resolved hyperfine interactions with three phosphorus nuclei. The Ti3+ ion is the intrinsic self-trapped electron center in KTP and has weak hyperfine interactions with four phosphorus nuclei.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349327
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  • 2
    Electronic Resource
    Electronic Resource
    Point defects in lithium triborate (LiB3O5) crystals (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 1114-1118 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electron paramagnetic resonance (EPR), electron-nuclear double resonance, optical absorption, and thermoluminescence have been used to investigate radiation-induced point defects in a single crystal of lithium triborate (LiB3O5). Two prominent defects are observed after irradiation near liquid-nitrogen temperature with 60 kV x rays. A four-line EPR spectrum, with 12.2 G splittings, is assigned to a trapped-hole center, and another four-line EPR spectrum, with 120 G splittings, is assigned to a trapped-electron center. In each case, the nucleus responsible for the observed hyperfine is 11B. The trapped hole is localized on an oxygen ion and has a weak hyperfine interaction with one neighboring boron nucleus, whereas the trapped electron is localized primarily on a boron ion with a correspondingly larger hyperfine interaction. Both defects become thermally unstable near 125 K, and their decay (i.e., recombination) correlates with an intense thermoluminescence peak at this same temperature. An optical absorption peak at 300 nm is produced by the x rays and thermally decays at the same temperatures as the EPR spectra.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353275
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of crystal growth on Ti3+ centers in KTiOPO4 (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 773-776 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A series of Ti3+ centers have been formed in hydrothermally grown and flux-grown potassium titanyl phosphate (KTiOPO4 or KTP). These 3d1 defects (S=1/2) were created with 60 kV x rays at 77 K, and electron paramagnetic resonance and electron-nuclear double-resonance (ENDOR) data were taken below 30 K. The ENDOR spectra show that the two Ti3+ centers having the largest concentrations in hydrothermally grown KTP have a neighboring proton, presumably in the form of an adjacent OH− ion. In contrast, ENDOR spectra show that neither of the two Ti3+ centers having the largest concentrations in flux-grown KTP have a neighboring proton. These significant differences in the local environment of the Ti3+ centers may help explain why KTP crystals have shown differing susceptibilities to gray tracking.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357780
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  • 4
    Electronic Resource
    Electronic Resource
    Electron-nuclear double resonance of the zinc vacancy in ZnGeP2 (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 2670-2672 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electron-nuclear double resonance (ENDOR) has been used to identify the singly ionized zinc vacancy (VZn− center) in ZnGeP2. This S=1/2; defect is the dominant paramagnetic acceptor in the material, and it is associated with the absorption from 0.7 to 2.5 μm that limits the use of ZnGeP2 in optical parametric oscillators. The unpaired spin of the VZn− center is shared nearly equally by two phosphorus nuclei adjacent to the vacancy with little overlap of the wave function onto the other two phosphorus neighbors. Angular dependence of the ENDOR spectrum shows that the two primary 31P nuclei have nearly axial hyperfine matrices with unique axes pointing approximately toward the center of the vacancy. The internuclear axis for these two phosphorus makes an angle of 37.8° with the basal plane. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113120
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  • 5
    Electronic Resource
    Electronic Resource
    Electron paramagnetic resonance study of a native acceptor in as-grown ZnGeP2 (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 1615-1617 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electron paramagnetic resonance (EPR) has been used to investigate an acceptor in as-grown single crystals of ZnGeP2. The spectra are characterized by equally spaced triplets with 1:2:1 intensity ratios representing hyperfine interactions (varying from 35 to 55 G in magnitude) with two equivalent phosphorous nuclei. Their angular dependence shows that there are four crystallographically equivalent orientations of the defect. The principal values of the g matrix are 2.002, 2.021, and 2.074 and the corresponding principal axes, at one of the four sites, are the [011], [1¯00], and [01¯1] directions, respectively. Two possible models are suggested for this acceptor: Either a zinc vacancy (VZn) or a zinc ion on a germanium site (ZnGe). It also is suggested that the acceptor responsible for the EPR signal is the same acceptor, namely AL1, that gives rise to a dominant near-infrared absorption band.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111855
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  • 6
    Electronic Resource
    Electronic Resource
    Defects responsible for gray tracks in flux-grown KTiOPO4 (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 3428-3430 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electron paramagnetic resonance (EPR) has been used to identify the primary electron and hole traps responsible for "gray tracks'' in flux-grown KTiOPO4(KTP). Ionizing radiation (x rays) was used to produce the gray-track effect. During an irradiation at 0 °C, a broad absorption band peaking near 500 nm is introduced, the EPR spectra from a series of Ti3+ centers appear, and the dominant EPR spectrum associated with Fe3+ ions decreases significantly. Following the irradiation, the decay of the optical absorption and the Ti3+ centers, along with the growth of Fe3+ centers, were monitored over a period of 20 h at room temperature. Changes in the EPR spectra of the Ti3+ and Fe3+ centers during the anneal correlated with the decay of the induced optical absorption (i.e., gray track). These results demonstrate that Fe3+ centers are the primary hole trap and Ti4+-VO complexes are the primary electron trap responsible for gray track formation in flux-grown KTP crystals. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113376
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