Tuesday, 22 March 2016

Compositional defects

          These defects arise from impurity atom during original crystallization. Impurity atoms considered as defects in a perfect lattice are responsible for the functioning of most semiconductor devices.
          A substitutional impurity is created when a foreign atom substitutes for a parent atom in the lattice as shown in Fig.
Ex: In brass, zinc is a substitutional atom in the copper lattice.
          An interstitial impurity is a small sized atom occupying an interstice or space between the regularly positioned atoms; as shown in Fig.
Ex: In steel, carbon atoms occupy the interstitial position in the iron lattice.

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