2. Band Structures of Solids

3. Conductivity of Metals and Alloys

4. Conductivity in Other Materials

5. Semiconductors

6. Applications of Semiconductors

Electric field: The voltage gradient or volts per unit length.

Drift velocity: The average rate at which charge carriers move through a material under an electric or magnetic field.

Mobility: The ease with which a charge carrier moves through a material.

Dielectric constant: The ratio of a material's permittivity to the permittivity of a vacuum, indicating its relative ability to polarize and store charge, also known as relative permittivity.

(b) valence electrons in metals move easily

(c) electrons in semiconductors and insulators require breaking covalent bonds to move

(d) in ionically bonded materials, entire ions must diffuse to carry charge.

Conduction band: The energy levels electrons can occupy to enable conductivity.

Holes: Unfilled energy levels in the valence band that facilitate current as electrons move to fill them.

Energy gap (Band gap): The energy difference between the top of the valence band and the bottom of the conduction band that a charge carrier must overcome to transfer a charge.

(b) When the temperature is increased, some electrons are excited into unfilled levels. Note that the Fermi energy is unchanged

(b) semiconductors, and

(c) dielectrics or insulators. (Temperature is 0 K.)

- Temperature Effect: Increased temperature causes metal atoms to vibrate, affecting electron movement.

- Effect of Atomic Level Defects: Crystal structure imperfections scatter electrons, reducing mobility and conductivity.

- Matthiessen’s rule: The resistivity of a metal is the sum of temperature-dependent resistivity (ρT) and a temperature-independent term due to atomic defects and impurities (ρd).

- Effect of Processing and Strengthening: Not explicitly defined, likely refers to how material processing and strengthening methods impact conductivity and other properties.

(b) the effect of addition of selected elements on the electrical conductivity of copper

- Conduction in Polymers: Low electrical conductivity due to valence electrons being involved in covalent bonding and a large energy gap in their band structure.

- Extrinsic semiconductor: A semiconductor whose properties are modified by adding dopants to control the number and type of charge carriers.

- Doping: The intentional addition of controlled amounts of other elements to increase the number of charge carriers in a semiconductor.

- Thermistor: A semiconductor device highly sensitive to temperature changes, used for precise temperature measurements.

- Radiative recombination: The process where holes and electrons recombine, emitting light, occurring in direct bandgap materials.

- Forward bias: Connecting a p-n junction so the p-side is positive, reducing the energy barrier and allowing significant current flow.

- Reverse bias: Connecting a p-n junction so the p-side is negative, resulting in minimal current flow.

- Avalanche breakdown: A reverse-bias voltage causing a large current in a lightly doped p-n junction.

- Transistor: A semiconductor device used to amplify electrical signals.