IMPORTANT NOTES
1. Materials that permit the flow of electrons are called conductors (e.g., Gold, Silver, Copper, etc.)
2. Materials that block the flow of electrons are called insulators (e.g., Rubber, Glass, Teflon, Mica, etc.)
3. Materials whose conductivity falls between those of conductors and insulators are called semiconductors.
4. Semiconductors are "part-time" conductors whose conductivity can be controlled. (e.g., Silicon, Germanium.)
5. Silicon is the most common material used to build semiconductors devices
6. Silicion is the main ingredient of sand and it is estimated that a cubic mile of seawater contains 15,000 tons of Silicon.
7. Silicon is spun and grown into a crystalline structure and cut into wafers to make electronic devices.
8. Atoms in a pure silicon wafer contains 4 electrons in outer orbit. (called valence electrons)
- Germanium is another semiconductor material with 4 valence electrons.
9. Ins crystalline lattice structure of Silicon, the valence electrons of every Silicon atom are locked up in covalent bonds with the valence electrons of 4 neighboring Silicon atoms.
- In pure form, Silicon wafer does not contain any free charge carriers.
- An applied voltage across pure Silicon wafers does not yield electron flow through the wafer.
- A pure Silicon wafer is said to act as an insulator.
