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  • 1
    Electronic Resource
    Electronic Resource
    Positron lifetime and 2D-ACAR studies of divacancies in Si (1995)
    Springer
    Applied physics 61 (1995), S. 65-70 
    Details
    ISSN: 1432-0630
    Keywords: PACS: 78.70; 61.70; 61.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract.  We have measured positron lifetime and Two Dimensional Angular Correlation of Annihilation Radiation (2D-ACAR) distributions of Floating-Zone grown (FZ) Si specimens containing divacancies (V2) with the definite charge states, V0 2, V-1 2 or V-2 2 from room temperature to about 10 K. These charge states are accomplished by an appropriate combination of dopant species, their concentration and irradiation doses of 15 MeV electrons with reference to the currently accepted ionization level of divacancies. The positron lifetime of the negatively charged divacancy increases with temperature, while that of the neutral divacancy shows little change with temperature. The positron trapping rate, obtained from lifetime and 2D-ACAR measurements, increases markedly with decreasing temperature. This is found not only for the negative divacancies but also for the neutral divacancy. We need a model which explains this temperature dependence. The 2D-ACAR distribution from positrons trapped at divacancies shows nearly the same distribution for the different charge states, which differs considerably from the case of As vacancies in GaAs studied by Ambigapathy et al. We have observed a small but definite anisotropy in the distribution of trapped positrons in V- 2 using a specimen containing oriented divacancies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01538213
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  • 2
    Electronic Resource
    Electronic Resource
    Vacancies and deep levels in electron-irradiated 6H SiC epilayers studied by positron annihilation and deep level transient spectroscopy (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 3377-3382 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The annealing behavior of defects in n-type 6H SiC epilayers irradiated with 2 MeV electrons have been studied using positron annihilation and deep level transient spectroscopy. Vacancy-type defects are annealed at 500–700 °C and 1200–1400 °C. From the analysis of Doppler broadening spectra (core electron momentum distribution), the latter annealing process is attributed to the disappearance of complexes related to silicon vacancies and not to nearest neighbor divacancies. Among the observed deep levels, the E1/E2 levels show similar annealing behavior to that of positron annihilation centers above 1000 °C. It is thus proposed that the E1/E2 levels originate from complexes containing silicon vacancies. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1402144
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  • 3
    Electronic Resource
    Electronic Resource
    Annealing behavior of vacancies and Z1/2 levels in electron-irradiated 4H–SiC studied by positron annihilation and deep-level transient spectroscopy (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 3950-3952 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Annealing behavior of vacancies and the Z1/2 levels in n-type 4H–SiC epilayers after 2 MeV electron irradiation has been studied using positron annihilation and deep-level transient spectroscopy. Isochronal annealing studies indicate that silicon vacancy-related defects are primarily responsible for positron trapping. The Z1/2 levels are the predominant deep centers after irradiation and subsequent annealing at 1200 °C. Both the positron-trapping rate at vacancies and the Z1/2 concentration decrease in a similar manner while annealing from 1200 to 1500 °C. It is thus proposed that the Z1/2 levels originate from silicon vacancy-related defects. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1426259
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of hydrogen etching on 6H SiC surface morphology studied by reflection high-energy positron diffraction and atomic force microscopy (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 1119-1121 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hydrogen-etched 6H SiC (0001) surfaces have been studied by reflection high-energy positron diffraction and atomic force microscopy. It was found that residual damage on the surfaces were effectively removed by the hydrogen etching as compared to the HF etching after the oxidation. The hydrogen-etched surfaces were atomically flat. After the oxidation following the hydrogen etching, the surface roughness was found to increase and an anomalous dip structure appeared in the rocking curve of the reflection high-energy positron diffraction. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.125957
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  • 5
    Electronic Resource
    Electronic Resource
    Silicon vacancies in 3C-SiC observed by positron lifetime and electron spin resonance (1998)
    Springer
    Applied physics 67 (1998), S. 209-212 
    Details
    ISSN: 1432-0630
    Keywords: PACS: 71.60+z; 61.72.Ji; 61.80.Fe
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: 54 , 2512 (1996)]. The trapping coefficient of single-negative silicon vacancies was also derived.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003390050759
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  • 6
    Electronic Resource
    Electronic Resource
    Positron lifetime and 2D-ACAR studies of divacancies in Si (1995)
    Springer
    Applied physics 61 (1995), S. 65-70 
    Details
    ISSN: 1432-0630
    Keywords: 78.70 ; 61.70 ; 61.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract We have measured positron lifetime and Two Dimensional Angular Correlation of Annihilation Radiation (2D-ACAR) distributions of Floating-Zone grown (FZ) Si specimens containing divacancies (V2) with the definite charge states, V 2 0 , V 2 −1 or V 2 −2 from room temperature to about 10 K. These charge states are accomplished by an appropriate combination of dopant species, their concentration and irradiation doses of 15 MeV electrons. with reference to the currently accepted ionization level of divacancies. The positron lifetime of the negatively charged divacancy increases with temperature, while that of the neutral divacancy shows little change with temperature. The positron trapping rate, obtained from lifetime and 2D-ACAR measurements, increases markedly with decreasing temperature. This is found not only for the negative divacancies but also for the neutral divacancy. We need a model which explains this temperature dependence. The 2D-ACAR distribution from positrons trapped at divacancies shows nearly the same distribution for the different charge states, which differs considerably from the case of As vacancies in GaAs studied by Ambigapathy et al. We have observed a small but definite anisotropy in the distribution of trapped positrons in V 2 − using a specimen containing oriented divacancies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01538213
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Studies of divacancy in Si using positron lifetime measurement (1994)
    Springer
    Hyperfine interactions 84 (1994), S. 397-406 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The charge state dependence of positron lifetime and trapping at divacancy (V2) in Si doped with phosphorus or boron has been studied after 15 McV electron irradiation up to a fluence of 8.0×1017 e/cm2. The positron trapping cross sections for V 2 2− , V 2 − and V 2 0 at 300 K were about 6×10−14, 3×10−14 and 0.1–3×10−14 cm2, respectively. For V 2 + , however, no positron trapping was observed. The marked difference in the cross sections comes from Coulomb interaction between the positron and the charged divacancy. The trapping rates for V 2 0 and V 2 2− have been found to increase with decreasing temperature in the temperature range of 10–300 K. These results are well interpreted by a two-stage trapping model having shallow levels with energy of 9 meV (V 2 0 ) and 21 meV (V 2 2− ). The appearance of a shallow level for V 2 0 can not be explained by a conventional “Rydberg state” model. The lifetime (290–300 ps) in V 2 0 is nearly constant in the temperature range from 10 to 300 K, while that in V 2 2− increases from 260 ps at 10 K to 320 ps at 300 K. The lifetime (260 ps) in V 2 2− is shorter than that in V 2 0 at low temperature, which is due to the excess electron density in V 2 2− . At high temperature, however, the longer lifetime of V 2 2− than that of V 2 0 is attributed to lattice relaxation around V 2 2− .
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02060688
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