Classify metals, semiconductors and insulators based on band theory of solids.

Asked by aishwarya S | 17th Oct, 2013, 12:17: PM

Expert Answer:

Classification of metals, semiconductors and insulators on the basis of band theory of solids:

1. Metals - The conduction band and valence band partly overlap each other and there is no forbidden energy gap.

2. Semiconductors - The conduction band is empty and valence band is totally filled at 0K but the forbidden gap between the two bands is quite small. No electron from valence band can cross over to conduction band at 0K, due to which semiconductors behave as insulators at 0K. At room temperature, some electrons in the valence band acquire thermal energy greater than the energy gap and jump over to conduction band. So, the semiconductor acquires small conductivity at room temperature.

3. Insulators - The conduction band is empty and valence band is completely filled but the forbidden gap is very large. No electron from valence band can cross over to conduction band at room temperature even if electric field is applied. Hence there is no conductivity of the insulators.

Answered by  | 17th Oct, 2013, 01:31: PM

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