• Shyam Singh

      Articles written in Bulletin of Materials Science

    • Loss of oxygen and carbon during donor formation in CZ-silicon

      O M Prakash Shyam Singh

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      Due to a lack of proper understanding about the formation mechanism of oxygen related donors during the transition temperature range (465–540°C) which exhibits the transition of TDs to NDs, an attempt has been made to study their behaviour in the present context. We have found the formation and diffusion of molecule like oxygen at low temperature annealing of silicon and observed that second order kinetics of oxygen diffusion holds good. A relatively low value of 0·6 eV has been estimated to be the activation energy for the diffusion of oxygen in silicon which is supposed to be due to the hydrogen passivation.

    • Formation of oxygen related donors in step-annealed CZ–silicon

      Vikash Dubey Shyam Singh

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      The effect of step-annealing necessitated by the difficulties being faced in the long duration annealing treatments to be given to CZ–silicon has been studied. One pre-anneal of 10 h followed by annealing of 10 h causes a decrease in the absorption coefficient for carbon (𝛼c). Oxygen and carbon both accelerate thermal donor (TD) formation process but oxygen plays a dominating role. Three anneals of 10 h each followed by one anneal of 10 h support the view that carbon suppresses the donor formation. The absorption coefficient for carbon decreases after a few number of step-anneals resulting in the transformation of TD to new donor (ND) as brought about by annealing at temperature, > 500°C. It is quite logical to conclude that step-annealing may bring about the same results as obtained on continuous annealing for a longer duration.

      The results have been fully supported by proper interpretation in the light of existing theories.

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