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  • 1
    Electronic Resource
    Electronic Resource
    On the temperature dependence of positron lifetimes in tin and the transition from theβ- to theα-phase (1983)
    Springer
    Applied physics 32 (1983), S. 183-185 
    Details
    ISSN: 1432-0630
    Keywords: 78.70 ; 61.70 ; 81
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract For the first time the positron lifetimes in polycrystalline tin have been measured as a function of temperature in the whole range from 80 K to the melting point. The temperature dependence of the mean lifetime could be divided into four regions which can be attributed to the depletion of shallow traps, normal thermal expansion, prevacancy effects, and trapping by vacancies, respectively. In one of the samples the phase transition fromβ- toα-Sn clearly could be detected at 230 K by a sharp increase in the mean lifetime.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00820258
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  • 2
    Electronic Resource
    Electronic Resource
    An investigation of point defects in silicon carbide (1995)
    Springer
    Applied physics 61 (1995), S. 55-58 
    Details
    ISSN: 1432-0630
    Keywords: PACS: 61.70; 68.55; 78.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract.  Positron lifetime measurements on bulk samples of single crystal SiC wafers have shown that both 6H and 4H polytypes exhibit a bulk lifetime of 150±2 ps. All samples contained a second, defect-related lifetime component, ranging in value from 250 to about 300 ps with rather low intensities. The defect structure exhibited by the nanocrystalline samples is, not unexpectedly, much more complex. Positron beam experiments on Electron Cyclotron Resonance Chemical Vapour Deposited (ECR-CVD) SiC thin films showed that the positrons are very sensitive to changes in important film parameters as a function of the deposition conditions. It was found that the film density is lower than expected, probably due to hydrogen incorporation; variations in composition among different films were detected through variations in the S parameters, and differences were observed in the electric field at the film–substrate interface due to hydrogen passivation of dangling bonds and different substrate resistivities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01538211
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  • 3
    Electronic Resource
    Electronic Resource
    Evidence for trapping of positrons in thallium
    Amsterdam : Elsevier
    Physics Letters A 112 (1985), S. 90-92 
    Details
    ISSN: 0375-9601
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0375-9601(85)90473-6
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of annealing on the defect structure in a-SiC:H films (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 2216-2223 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The annealing behavior of amorphous, hydrogenated silicon carbide films in the range 400–900 °C was studied by optical characterization methods, 15N hydrogen profiling, and defect profiling using a variable energy positron beam. The films were deposited in an electron cyclotron resonance chemical vapor deposition system using ditertiary butyl silane [SiH2(C4H9)2] as the monosource for silicon and carbon. As-deposited films were found to contain large concentrations of hydrogen, both bonded and unbonded. Under rapid thermal annealing in a N2 atmosphere, the bonded hydrogen effuses giving rise to additional Si–C bond formation and to film densification. After annealing at high temperatures in N2, a marked decrease in the total hydrogen content is observed. After annealing in vacuum, however, the hydrogen effusion promotes void formation in the films. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363049
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  • 5
    Electronic Resource
    Electronic Resource
    Annealing studies of vacancies in proton irradiated silicon (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 3740-3743 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Annealing of vacancies produced by heavy proton irradiation of float-zone (Fz) and P-doped Czochralski-grown (Cz) silicon has been investigated by positron lifetime spectroscopy. In Fz-Si divacancies are retained after irradiation, and these defects are completely annealed out at 700 °C. In Cz P-doped silicon, impurities are found to enhance both the amount of retained vacancies as well as the tendency for vacancy clustering. Two annealing stages appear at 100 °C and close to 450 °C which seem to be a result of interstitial migration. Vacancy migration takes place in a wide temperature range between 100 and 1000 °C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352905
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  • 6
    Electronic Resource
    Electronic Resource
    Heat-treatment-induced defects in low-resistivity silicon (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 3526-3534 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Czochralski-grown silicon has been investigated with doping levels up to 5×1018 cm−3 of boron or phosphorus by positron annihilation. For the highly boron-doped samples vacancies could be created upon heat treatment in the 700–1000 °C range up to a concentration of 1017 vacancies cm−3. Reducing either the boron concentration or the interstitial oxygen concentration (by prolonged heat treatment at 1200 °C) reduced the amount of created vacancies. No vacancies were detected in highly phosphorus-doped materials. Combined positron-lifetime and Doppler-broadening measurements indicate that the vacancies are essentially of monovacancy nature and have impurities close by which contribute with high-momentum electrons. Isothermal heat treatments at 700, 750, 900, and 950 °C indicate a reaction of the form X+Y(arrow-right-and-left)Z, where Z contains a vacancy. The forward reaction has an activation enthalpy of 2.7 eV, while the back reaction has the value 3.0 eV. It is suggested that X corresponds to substitutional boron and Y to interstitial oxygen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344110
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  • 7
    Electronic Resource
    Electronic Resource
    Deformation-induced defects in GaAs (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 4080-4091 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Semi-insulating undoped GaAs was plastically deformed and then investigated by positron lifetime spectroscopy. Strains between 0% and 40% and temperatures of deformation of 450, 500, and 600 °C were investigated, with detailed investigations carried out for the lowest temperature of deformation. Between 0% and 4% strain a reduction of the grown-in vacancy response takes place simultaneously with a slight increase in vacancy cluster size to 2 or 3 vacancies. Between 4% and 6% strain a very substantial increase in vacancy production occurs but nearly all of these vacancies are clustered into voids with a radius of about 50 A(ring) and density of the order of 1013–1014 cm−3. The total concentration of vacancies necessary to produce these voids is 1017–1018 cm−3. This clearly shows that vacancies are formed upon deformation and that they are mobile at 450 °C. The small vacancy clusters (2 or 3 vacancies) are present at a concentration of about 5×1016 cm−3, the same as for the 4% strained samples. Upon further deformation to 20% strain the overall defect concentration becomes so high that all positrons become trapped for which reason no absolute defect concentrations can be deduced. The dominant defect types can nevertheless be identified as voids (with average size of 20 A(ring)), two- or three-vacancy clusters, and shallow traps. These shallow traps have a positron binding energy of about 40 meV. Isochronal and isothermal annealing of 40% strained samples shows that heat treatment reduces the void concentration but increases the average void size, reduces the small vacancy cluster concentration, but results only in a small decrease in shallow trap concentration. The shallow traps are likely the dislocation lines themselves and the small vacancy clusters appear to be associated with the dislocation lines.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348420
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  • 8
    Electronic Resource
    Electronic Resource
    Refractive indices of InGaAsP lattice-matched to GaAs at wavelengths relevant to device design (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 2791-2793 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The refractive indices of In1−xGaxAsyP1−y grown lattice-matched to GaAs by gas-source molecular-beam epitaxy, have been measured by variable angle spectroscopic ellipsometry. Indices in the transparent regime of these quaternaries, at 980 and 808 nm (relevant to the design of pump sources for erbium-doped fiber amplifiers and Nd:YAG lasers, respectively) and at 850 nm, are presented. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.126477
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  • 9
    Electronic Resource
    Electronic Resource
    On the contribution of vacancy complexes to the saturation of the carrier concentration in zinc doped InP (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 2712-2719 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Positron annihilation spectroscopy on Zn-doped InP has revealed the presence of a defect with a positron lifetime of ∼330 ps in samples in which the carrier concentration has saturated. This lifetime is attributed to a complex involving vacancies and Zn atoms. A model is proposed in which this complex has a (−/0) level near the bottom of the band gap, and undergoes a large inward lattice relaxation upon the transition to the neutral charge state, causing a reduction in the positron lifetime to ∼281 ps. This model explains the positron annihilation results on annealed samples and at low temperatures, and is supported by Hall effect measurements. The concentration of these complexes is less than 1017 cm−3. Therefore, these complexes cannot solely account for the observed discrepancy between the carrier concentration and the Zn concentration in very heavily Zn-doped InP. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363188
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  • 10
    Electronic Resource
    Electronic Resource
    In-situ monitoring of electron cyclotron resonance plasma chemical vapour deposition of hydrogenated silicon nitride films
    Amsterdam : Elsevier
    Surface & Coatings Technology 59 (1993), S. 77-81 
    Details
    ISSN: 0257-8972
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0257-8972(93)90057-U
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