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  • 1
    Electronic Resource
    Electronic Resource
    Defects in ion-implanted crystalline silicon probed by femtosecond laser spectroscopy (1996)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 18 (1996), S. 595-603 
    Details
    ISSN: 0392-6737
    Keywords: Defects in crystals ; Point defects (vacancies, interstitials, color centers, etc.) and defect clusters ; Ions ; Ultrafast processes ; optical pulse generation and pulse compression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary Radiation damage is generated in a controlled manner by MeV ion implantation of Si+ and He+ ions in c-Si and studied by ultrafast laser pulses on a subpicosecond time scale. In Si+-implanted samples the amorphization of the sample is achieved at sufficiently high doses, while He implants only produce a very low level of damage. Defects are investigated after implantation by measuringex situ the change of reflectivity caused by a high density of electron-hole plasma generated by femtosecond laser pulses. The plasma decay time decreases as a function of the implantation dose in both Si- and He-implanted samples, reaching a minimum value of ≈1 ps. It is observed that the saturation of the decay time is not related to the amorphization of the sample, but rather to the formation of simple defects produced during ion implantation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02453250
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  • 2
    Electronic Resource
    Electronic Resource
    Epitaxial explosive crystallization of amorphous silicon (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 1097-1099 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It is shown that amorphous silicon can be transformed to monocrystalline silicon via an explosive epitaxial crystallization process induced by pulsed laser irradiation. 370-nm-thick amorphous Si layers, buried beneath a 130-nm-thick crystalline surface layer, were irradiated with a 32 ns ruby laser pulse. Real-time reflectivity measurements indicate that internal melting can be initiated at the amorphous-crystalline interface, immediately followed by explosive crystallization of the buried amorphous Si layer. Channeling and cross-sectional transmission electron microscopy reveal that explosive crystallization proceeds epitaxially with formation of twins extending into the sample. The crystal growth velocity is determined to be 16.2±1.2 m/s, close to the fundamental limit for crystalline ordering at a liquid Si/Si(100) interface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101668
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  • 3
    Electronic Resource
    Electronic Resource
    Implantation and transient B diffusion in Si: The source of the interstitials (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 2305-2307 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Implanted B and P dopants in Si exhibit transient enhanced diffusion (TED) during initial annealing, due to Si interstitials being emitted from the region of the implant damage. The structural source of these interstitials has not previously been identified. Quantitative transmission electron microscopy measurements of extended defects are used to demonstrate that TED is caused by the emission of interstitials from specific defects. The defects are rodlike defects running along 〈110〉 directions, which consist of interstitials precipitating on {311} planes as a single monolayer of hexagonal Si. We correlate the evaporation of {311} defects during annealing at 670 and 815 °C with the length of the diffusion transient, and demonstrate a link between the number of interstitials emitted by the defects, and the flux of interstitials driving TED. Thus not only are {311} defects contributing to the interstitial flux, but the contribution attributable to {311} defect evaporation is sufficient to explain the whole of the observed transient. The {311} defects are the source of the interstitials. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112725
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  • 4
    Electronic Resource
    Electronic Resource
    Physical mechanisms of transient enhanced dopant diffusion in ion-implanted silicon (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 6031-6050 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Implanted B and P dopants in Si exhibit transient enhanced diffusion (TED) during annealing which arises from the excess interstitials generated by the implant. In order to study the mechanisms of TED, transmission electron microscopy measurements of implantation damage were combined with B diffusion experiments using doping marker structures grown by molecular-beam epitaxy (MBE). Damage from nonamorphizing Si implants at doses ranging from 5×1012 to 1×1014/cm2 evolves into a distribution of {311} interstitial agglomerates during the initial annealing stages at 670–815 °C. The excess interstitial concentration contained in these defects roughly equals the implanted ion dose, an observation that is corroborated by atomistic Monte Carlo simulations of implantation and annealing processes. The injection of interstitials from the damage region involves the dissolution of {311} defects during Ostwald ripening with an activation energy of 3.8±0.2 eV. The excess interstitials drive substitutional B into electrically inactive, metastable clusters of presumably two or three B atoms at concentrations below the solid solubility, thus explaining the generally observed immobile B peak during TED of ion-implanted B. Injected interstitials undergo retarded diffusion in the MBE-grown Si with an effective migration energy of ∼3.5 eV, which arises from trapping at substitutional C. The concept of trap-limited diffusion provides a stepping stone for understanding the enormous disparity among published values for the interstitial diffusivity in Si. The population of excess interstitials is strongly reduced by incorporating substitutional C in Si to levels of ∼1019/cm3 prior to ion implantation. This provides a promising method for suppressing TED, thus enabling shallow junction formation in future Si devices through dopant implantation. The present insights have been implemented into a process simulator, allowing for a significant improvement of the predictive modeling of TED. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364452
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  • 5
    Electronic Resource
    Electronic Resource
    Formation of extended defects in silicon by high energy implantation of B and P (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 2105-2112 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The extended defects induced in silicon by high energy implantation (1.5 MeV B and 2.6 MeV P) have been investigated by plan-view and cross-sectional transmission electron microscopy studies and defect etching measurements. The threading dislocations were identified to be long dislocation dipoles generated in the region of the ion projected range which grew up to the surface. The formation of threading dislocations is shown to have a strong dependence on the implantation dose and O concentration. After 900 °C annealing, a high density of threading dislocations was formed for B and P implants in a dose range of 5×1013–2×1014 cm−2 and 5×1013–3×1014 cm−2, respectively. The threading dislocation density in B-implanted Czochralski Si substrates was found to be much higher than that in B-implanted epitaxial Si substrates. This difference is attributed to the strong pinning effect of oxygen immobilizing dislocations in Czochralski substrates. Because P impurities are also efficient at pinning dislocation motion in Si, a high density of threading dislocations was observed even in epitaxial Si substrates with P implantation. Two-step annealing with a first step at 700 °C (to precipitate oxygen) and a second step at 900 °C was found to be very effective at eliminating the formation of threading dislocations. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363103
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  • 6
    Electronic Resource
    Electronic Resource
    Contribution of defects to electronic, structural, and thermodynamic properties of amorphous silicon (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 7266-7286 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The structure of pure, nonhydrogenated amorphous silicon (a-Si) was modified by means of ion implantation, furnace annealing, and pulsed laser annealing. Defects in a-Si were probed by measuring the photocarrier lifetime τ at low carrier densities (1018/cm3) with subpicosecond resolution using pump-probe reflectivity measurements. The average cross section of defect-related midgap states for free-carrier capture is found to be 6×10−16 cm2. In addition, the average bond-angle distortion Δθ in a-Si was derived from Raman spectroscopy. Annealing as-implanted a-Si for 1 h at T≤500 °C induces defect annihilation as well as network relaxation. In contrast, 32 ns pulsed laser heating of a-Si just below the melting threshold leads to relaxation of Δθ without significant defect annihilation. This annealing behavior can be understood on the basis of defect diffusion kinetics. Implanting fully relaxed a-Si with 1 MeV B+, Si+, and Xe+ up to damage levels of 0.004 displacements per atom raises the defect density without affecting Δθ. Only after the defect density has saturated at higher damage levels is Δθ returned to the as-implanted level. The electronic density of states of a-Si is determined using optical-absorption spectroscopy, yielding Nsat≈0.5 at. % for the saturation defect density in a-Si at room temperature. Electron paramagnetic resonance shows that a minor fraction (0.02 at. %) of these defects is spin active. The response of c-Si and relaxed a-Si to implantation damage is comparable, suggesting that the defect populations in both materials are similar. Comparing carrier lifetime measurements and Raman spectroscopy for the various experimental treatments demonstrates that there is no unique correlation between the defect density and Δθ in a-Si. Assuming that defects and Δθ have independent enthalpic contributions, the Gibbs free energy of various structural states of a-Si is calculated. These calculations indicate that the melting temperature of a-Si may vary from 1010 to 1490 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356662
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  • 7
    Electronic Resource
    Electronic Resource
    Pulsed-laser crystallization of amorphous silicon layers buried in a crystalline matrix (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 4024-4035 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ion implantation, employing Si, Ar, and Cu ions in the energy range from 275 to 600 keV, was used to form amorphous silicon layers buried in a crystalline matrix. Different layer geometries were produced, with 150–620-nm-thick amorphous layers, separated from the surface by 120–350-nm-thick crystalline layers. Crystallization of the amorphous layers was induced by 32-ns pulsed ruby laser irradiation. Real-time reflectivity and conductivity measurements indicate that internal melting can be initiated at the amorphous-crystalline interface, immediately followed by explosive crystallization of the buried layer. Channeling and cross-section transmission electron microscopy reveal that in both Si(100) and Si(111) samples explosive crystallization proceeds epitaxially with twin formation, the twin density being higher in Si(111) than in Si(100). The measured crystal growth velocities range from 15 to 16 m/s, close to the fundamental limit for crystalline ordering at a Si liquid-crystalline interface. Computer modeling of heat flow and phase transformations supports the experimental data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346076
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  • 8
    Electronic Resource
    Electronic Resource
    Structural and electrical defects in amorphous silicon probed by positrons and electrons (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 5145-5152 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The structure of pure amorphous Si, prepared by ion implantation, has been investigated by variable-energy positron annihilation spectroscopy (PAS) and lifetime measurements of optically generated free carriers. In general, PAS measurements are thought to be sensitive to vacancy-type defects while the carrier lifetime depends on the density of band-gap states (e.g., dangling bonds). The PAS measurements indicate that the density of positron-trapping defects can be reduced by thermal annealing at 500 °C. Concurrent with the removal of structural defects the density of band gap states is reduced as indicated by an increased photocarrier lifetime by a factor of 10. Some material has been implanted with H+ and annealed at a low temperature (150 °C). The hydrogen is expected to passivate electrical defects associated with strained and dangling bonds and indeed the photocarrier lifetime is increased in this material. Moreover, the PAS measurements cannot distinguish this material from 500 °C annealed amorphous Si, indicating that (some of) the electrical defects are associated with positron-trapping, and therefore possibly vacancy-type, structural defects. Finally, both methods have been used to detect small amounts of ion irradiation damage in annealed amorphous Si.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351993
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  • 9
    Electronic Resource
    Electronic Resource
    Effect of heating ramp rates on transient enhanced diffusion in ion-implanted silicon (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 889-891 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Boron marker-layer structures have been used to analyze the heating ramp-rate dependence of transient enhanced dopant diffusion (TED) during rapid thermal annealing of Si implantation damage. The study uses short anneals with heating ramp rates in the range 0.1–350 °C/s, and peak temperatures in the range 900–1100 °C. Increasing the ramp rate is found to reduce the amount of profile broadening caused by TED, as well as reducing the smaller amount of normal "thermal-equilibrium" diffusion which is related to thermal budget. The results show why high ramp rates lead to improved B-implant activation and junction-depth control in Si devices. An Ostwald ripening model of interstitial-cluster evolution describes the detailed trends in the data and predicts further improvements in the case of ultrarapid annealing. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1347397
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  • 10
    Electronic Resource
    Electronic Resource
    Interactions of ion-implantation-induced interstitials with boron at high concentrations in silicon (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 1376-1378 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ion implantation of Si (60 keV, 1×1014/cm2) has been used to introduce excess interstitials into silicon predoped with high background concentrations of B, which were varied between 1×1018 and 1×1019/cm3. Following post-implantation annealing at 740 °C for 15 min to allow agglomeration of the available interstitials into elongated {311} defects, the density of the agglomerated interstitials was determined by plan-view transmission electron microscopy observation of the defects. We report a significant reduction in the fraction of excess interstitials trapped in {311} defects as a function of boron concentration, up to nearly complete disappearance of the {311} defects at boron concentrations of 1×1019/cm3. The reduction of the excess interstitial concentration is interpreted in terms of boron-interstitial clustering, and implications for transient-enhanced diffusion of B at high concentrations are discussed. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117441
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