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Mada za sehemu hiiElectronicsMada 6

Introduction to energy bands In isolated atoms, electrons occupy discrete energy levels (orbits). In solids, atoms are closely packed, causing the outer electrons' energy levels to overlap due to mutual interaction. These overlapping energy levels form energy bands: a range of allowed energies for electrons.

Material Band Structure Example Conductors Valence and conduction bands overlap (no band gap) Copper, Aluminium Semiconductors Small band gap (e.g., Si = 0.7 eV, Ge \approx 0.3 eV) Silicon, Germanium Insulators Large band gap (5-15 eV); very little conduction Glass, Mica, Wood

Material	Band Structure	Example
Conductors	Valence and conduction bands overlap (no band gap)	Copper, Aluminium
Semiconductors	Small band gap (e.g., Si = 0.7 eV, Ge ≈ 0.3 eV)	Silicon, Germanium
Insulators	Large band gap (5–15 eV); very little conduction	Glass, Mica, Wood

Material Effect of Increasing Temperature Conductors Decreased conductivity due to more atomic vibration (resistance increases) Semiconductors Increased conductivity as more electrons jump to conduction band Insulators No significant change (band gap too large); may conduct only at high T Superconductors Perfect conductivity near absolute zero (0 K)

Material	Effect of Increasing Temperature
Conductors	Decreased conductivity due to more atomic vibration (resistance increases)
Semiconductors	Increased conductivity as more electrons jump to conduction band
Insulators	No significant change (band gap too large); may conduct only at high T
Superconductors	Perfect conductivity near absolute zero (0 K)

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