The evolution of boron segregation to extended defects during thermal annealing was studied with secondary ion mass spectrometry and cross-sectional transmission electron microscopy. Czochralski Si wafers with a boron concentration of 3×1017 cm−3 were implanted with 50 keV Si ion for doses from 5×1013 to 2×1015 cm−2 and then annealed at 720, 820, or 870 °C in nitrogen ambient for various annealing times. The evolution of boron segregation peaks to three types of dislocation loops, end-of-range (EOR) dislocation loops, clamshell defects, and Rp (the projected range) defects, is closely related to the evolution of dislocation loops. As annealing temperature and time increase, the boron segregation peaks grow, remain stable, and then disappear together with the dislocation loops. For lower temperature annealing, the boron segregation peaks grow more slowly and reach higher peak concentrations. In addition to the boron segregation to dislocation loops, boron segregation to {311} defects was also found. The boron segregation peak to {311} defects is unstable and dissolves completely after annealing at 820 °C for 10 min. An analytic model for the boron segregation to EOR dislocation loops was developed under equilibrium condition by taking account of the average radius and area density of the EOR dislocation loops. The boron segregation energy to the EOR dislocation loops was found to be 0.75 eV. The evolution of the boron segregation peak was explained with the analytic model. The experimental boron segregation profiles can be well reproduced with the analytic model.

We construct a kink solution on a non-BPS D-brane using Berkovits' formulation of superstring field theory in the level truncation scheme. The tension of the kink reproduces 95% of the expected BPS D-brane tension. We also find a lump-like solution which is interpreted as a kink-antikink pair, and investigate some of its properties. These results may be considered as successful tests of Berkovits' superstring field theory combined with the modified level truncation scheme.

SUMMARYWe have observed transient enhanced diffusion (TED) in silicon substrates with boron doping superlattices and varying background carbon concentrations after ion implantation with silicon ions followed by low-temperature annealing. Our results clarify the effects of low-level carbon concentrations on this process. In addition, we have found that the effective diffusion coefficient of self-interstitial Si atoms is inversely proportional to the square of the substrate carbon concentration. We also discovered that the carbon atoms segregate out in the ion-implantation damage regions, forming boroncarbon clusters.

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The transient behavior of P diffusion in Si implanted with As or Ge above the amorphizing threshold has been investigated. Annealing at 720 °C after Ge implantation induces extensive P segregation into the extended defect layer formed by implantation damage. This segregation is attributed to P trapping to end-of-range {311} defects and dislocation loops. For As implantation, P segregation was also observed only after 1 min annealing. However, in contrast to the Ge implantation, in the As-implanted samples, significant P depletion occurs in the As-tail region after further annealing. Nonequilibrium simulation that takes into account both Fermi-level and electric field effects shows the P depletion during transient enhanced diffusion. Furthermore, simulation results based on the coexistence of neutral and positively charged phosphorus-interstitial pairs agree well with the obtained experimental results.