In which of the following materials is the energy gap (Eg) between the top of the valence band and bottom of the conduction band is between greater than 0.5 eV and less than 3 eV?
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A.
Insulators
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B.
Semiconductors
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C.
Conductors
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D.
Superconductors
Correct Answer:
B. Semiconductors
Explanation:
Materials are classified into three primary categories based on the magnitude of their energy gap (Eg) between the valence and conduction bands. Conductors, such as metals, have no energy gap as their bands overlap, allowing for easy electron flow. Conversely, insulators possess a very large energy gap, typically exceeding 3 eV to 5 eV, which prevents electrons from moving into the conduction band under normal conditions.
Semiconductors fall between these two extremes, characterized by a moderate energy gap. In these materials, the energy gap is generally greater than 0.5 eV but less than 3 eV. This specific range allows electrons to be excited from the valence band to the conduction band through thermal energy or light, making them essential for electronic devices like transistors and LEDs. Common examples include Silicon (1.12 eV) and Germanium (0.66 eV).
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