Experiments to determine the mean depth scale of positrons in silicon: slow positron beam measurements on MBE-grown silicon layers on silicon oxide

Gebauer, J.; Eichler, S.; Krause‐Rehberg, R.; Zeindl, H.P.

doi:10.1016/s0169-4332(96)01063-x

Cited by 10 publications

(6 citation statements)

References 10 publications

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“…The median implantation depth as a function of energy could be described with the commonly used power-law fit with A ϭ2.81 (Ϯ0.2) g cm Ϫ2 and nϭ1.71(Ϯ0.05), in good agreement with experimental data on positron implantation in Al, Cu, Au, ZnS, Al 2 O 3 , and a-Si found in the literature. 11,12,15,18,35 Fitting of the Makhovian equation to P(z,E) suggested that the parameter m was independent of the positron implantation energy, but dependent on z at constant implantation energy. The fitted value of m in the Makhovian equation varied systematically between ca.…”

Section: Discussionmentioning

confidence: 99%

Median implantation depth and implantation profile of 3–18 keV positrons in amorphous polymers

et al. 2003

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Most applications of positron beams require knowledge of the implantation characteristics for an appropriate interpretation of the experimental data. In this work, the median implantation depth as a function of implantation energy, z 1/2 (E), of 3-18 keV positrons and their implantation profile P(z,E) in a total of 13 thin films of atactic polystyrene, poly͑styrene-co-acrylonitrile͒, and polymethylmethacrylate spin coated onto a silicon substrate were determined from positron lifetime measurements using a pulsed, low-energy positron beam. z 1/2 (E) and P(z,E) were determined from the measurement of the ortho-positronium yield obtained from the intensity I 3 of the long lifetime. z 1/2 (E) was parametrized with the commonly used power-law fit z 1/2 (E) ϭ(A/)E n , with and E in units of g cm Ϫ3 and keV, respectively, yielding Aϭ2.81(Ϯ0.2) g cm Ϫ2 and n ϭ1.71(Ϯ0.05). Excellent agreement between amorphous polymer and literature data on Al and Cu suggests that the median implantation depth of positrons for low-to medium-Z materials in the studied energy range is independent of structure and only a function of mass density. Fitting of the Makhovian implantation profile to the experimental data suggested that the value of the parameter m varies between 1.7 and 2.3, systematically increasing with z at constant implantation energy, but is independent of the implantation energy. Using an equation proposed by Baker et al., the experimental data of 12 of the 13 studied polymer films could be described with a slightly better agreement than the Makhovian equation.

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Section: Discussionmentioning

confidence: 99%

Median implantation depth and implantation profile of 3–18 keV positrons in amorphous polymers

et al. 2003

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“…Aϭ2.75 g cm Ϫ2 keV Ϫn and nϭ1.7 are empirical parameters for silicon. 12,13 After thermalization, positrons will diffuse in the solid until they annihilate. The diffusion can be described by the one-dimensional time-independent diffusion equation…”

Section: ͑2͒mentioning

confidence: 99%

Defects in silicon afterB+implantation: A study using a positron-beam technique, Rutherford backscattering, secondary neutral mass spectroscopy, and infrared absorption spectroscopy

et al. 1997

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The distribution of defects in Si ͑100͒, ͑110͒, and ͑111͒ after boron implantation and annealing processes was measured by means of different methods. Boron implantation was carried out at 300 K with three energies ͑50, 150, and 300 keV or 30, 90, and 180 keV͒ in multiple mode to obtain a homogeneously damaged layer. Ion fluences ranged from 10 14 to 10 16 B ϩ cm Ϫ2 . The profile of vacancy-type defects was detected by variableenergy positron annihilation spectroscopy ͑VEPAS͒. The defect concentration increases proportionally to ͱ⌽, where ⌽ is the ion fluence. It was found that the line-shape parameter S of the positron-electron annihilation peak in the implanted layer increases with ⌽. The divacancy (2v) concentration observed by infrared absorption spectroscopy ͑IRAS͒ was nearly constant in all samples ͑about 1.8ϫ10 19 cm Ϫ3 ͒. It can be concluded that divacancies are not the main vacancy-type defect and the increasing S parameter must be attributed to additional defects of larger open volume. A value S defect /S bulk ϭ1.048 was fitted for the dominating defect, where S 2v /S bulk ϭ1.04. Rutherford backscattering ͑RBS͒ measurements were carried out to detect the distribution of displaced lattice atoms. The defect-production rate was proportional to ͱ⌽ again. The concentration profiles of implanted ions were measured with sputtered neutral mass spectrometry ͑SNMS͒. In addition, Monte Carlo calculations were done with the TRIM code. The nearly homogenous defect distributions up to a depth of 1 m found by VEPAS, TRIM, and RBS are in very good accordance. The samples were annealed up to 1150 K. It was found that the annealing behavior of vacancylike defects depends on the implantation dose and on the sample material under investigation. The divacancies are annealed at 470 K as measured by IRAS. An annealing stage of vacancy clusters at 725 K was observed in all samples by VEPAS. In Czochralski material, a decrease of the S parameter below the value of defect-free Si was observed after annealing at about 750 K. This can only be explained by the appearance of a different defect type, most likely an oxygen-vacancy complex. At high ion fluences (10 16 B ϩ cm Ϫ2 ), an increase of the S parameter above the defect value at room temperature was observed after annealing at 700 K in a region 100 nm below the surface. This high S parameter is caused by the creation of larger vacancy clusters. These defects remain stable after annealing at 850 K. Correlated RBS and SNMS measurements were done at identically implanted samples for all annealing stages.

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“…The mean implantation depth of positrons z is shown on the upper horizontal axis, where the relationship between z and E was given in Ref. 35. For HVPE-GaN, the S value increased with decreasing E, which corresponds to the diffusion of positrons toward the surface: the large S values at low E (ffi0.1 keV) are associated with the annihilation of positrons at the surface.…”

Section: Resultsmentioning

confidence: 99%

Vacancy-type defects in Mg-doped GaN grown by ammonia-based molecular beam epitaxy probed using a monoenergetic positron beam

Uedono

Malinverni

Martin

et al. 2016

Journal of Applied Physics

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Vacancy-type defects in Mg-doped GaN were probed using a monoenergetic positron beam. GaN films with a thickness of 0.5–0.7 μm were grown on GaN/sapphire templates using ammonia-based molecular beam epitaxy and characterized by measuring Doppler broadening spectra. Although no vacancies were detected in samples with a Mg concentration [Mg] below 7 × 1019 cm−3, vacancy-type defects were introduced starting at above [Mg] = 1 × 1020 cm−3. The major defect species was identified as a complex between Ga vacancy (VGa) and multiple nitrogen vacancies (VNs). The introduction of vacancy complexes was found to correlate with a decrease in the net acceptor concentration, suggesting that the defect introduction is closely related to the carrier compensation. We also investigated Mg-doped GaN layers grown using In as the surfactant. The formation of vacancy complexes was suppressed in the subsurface region (≤80 nm). The observed depth distribution of defects was attributed to the thermal instability of the defects, which resulted in the introduction of vacancy complexes during the deposition process.

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Experiments to determine the mean depth scale of positrons in silicon: slow positron beam measurements on MBE-grown silicon layers on silicon oxide

Cited by 10 publications

References 10 publications

Median implantation depth and implantation profile of 3–18 keV positrons in amorphous polymers

Median implantation depth and implantation profile of 3–18 keV positrons in amorphous polymers

Defects in silicon afterB+implantation: A study using a positron-beam technique, Rutherford backscattering, secondary neutral mass spectroscopy, and infrared absorption spectroscopy

Vacancy-type defects in Mg-doped GaN grown by ammonia-based molecular beam epitaxy probed using a monoenergetic positron beam

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