Electronics: Conduction and Valence Bands

Band Theory

Conduction Bands

• A conduction band is a range of allowed energy states in a solid where electrons can move freely
• Electrons in the conduction band are delocalized, meaning they are not bound to a specific atom or molecule
• Conduction bands are responsible for the electrical conductivity of a material
• In metals, the conduction band is partially filled with electrons, allowing for easy flow of electricity

Valence Bands

• A valence band is a range of allowed energy states in a solid where electrons are localized and bound to specific atoms or molecules
• Electrons in the valence band are involved in chemical bonding and are not free to move
• Valence bands are responsible for the chemical properties of a material
• In insulators, the valence band is fully occupied with electrons, making it difficult for electricity to flow

Semiconductor Materials

• Semiconductor materials have a small energy gap (bandgap) between the valence and conduction bands
• This allows for some electrons to jump from the valence band to the conduction band, making them partially conductive
• Semiconductor materials can be doped with impurities to increase or decrease their conductivity
• Examples of semiconductor materials include silicon, germanium, and gallium arsenide

Molecular Orbitals

• Molecular orbitals are a way to describe the distribution of electrons within a molecule
• In band theory, molecular orbitals are used to describe the energy states of electrons in a solid
• Molecular orbitals can be bonding (low energy) or antibonding (high energy)
• The combination of molecular orbitals from individual atoms forms the valence and conduction bands

Electron Configuration

• Electron configuration refers to the arrangement of electrons in an atom or molecule
• In band theory, electron configuration is used to determine the energy states of electrons in a solid
• The electron configuration of individual atoms determines the shape and width of the valence and conduction bands
• Changes in electron configuration can affect the electrical conductivity of a material

Band Theory

Conduction Bands

• Conduction bands allow electrons to move freely in a solid due to delocalization, enabling electrical conductivity.
• Partially filled conduction bands in metals facilitate easy flow of electricity.
• The conduction band is a range of allowed energy states where electrons can move freely.

Valence Bands

• Valence bands are responsible for chemical properties, with electrons being localized and bound to specific atoms or molecules.
• Fully occupied valence bands in insulators make it difficult for electricity to flow.
• The valence band is a range of allowed energy states where electrons are localized and bound.

Semiconductor Materials

• Semiconductor materials have a small energy gap (bandgap) between valence and conduction bands, making them partially conductive.
• Doping semiconductor materials with impurities can increase or decrease their conductivity.
• Examples of semiconductor materials include silicon, germanium, and gallium arsenide.

Molecular Orbitals

• Molecular orbitals describe the distribution of electrons within a molecule and are used to describe energy states in a solid.
• Bonding molecular orbitals have low energy, while antibonding molecular orbitals have high energy.
• Combining molecular orbitals from individual atoms forms the valence and conduction bands.

Electron Configuration

• Electron configuration determines the energy states of electrons in a solid.
• The electron configuration of individual atoms determines the shape and width of the valence and conduction bands.
• Changes in electron configuration affect the electrical conductivity of a material.