Silicon: A silvery-colored semiconductor material used in today's integrated circuit technology. Transistor:
An electronic device that controls current flow and serves as the basic element of a computer chip. Consists of three terminals: a source, a gate, and a drain. Applying a voltage to the gate controls current flow between the source and the drain. Integrated chip: An electrical circuit consisting of millions
of transistors, wires, and other devices built onto a centimeter-square piece of silicon. Moore's Law: A tenet that says the density of transistors on integrated circuits--and, therefore, the speed of the
chips--doubles roughly every 18 months. Photolithography: A method for constructing integrated chips, layer by layer. A silicon chip is coated with a
chemical called a photoresist. Flashing a pattern of light and dark onto the photoresist causes it to harden in the areas exposed to light. The parts not exposed to light stay soft and are etched away. The
process is repeated to deposit subsequent layers of material onto the chip. A photolithographic manufacturing process can take hundreds of separate steps, but hundreds of chips are built onto a
single silicon wafer at the same time. Molecular electronics: A new approach to making integrated chips using organic molecules instead of silicon as transistors, wires, and other electronic devices. Carbon nanotubes: Tiny, hollow tubes made of pure
carbon just a few nanometers in diameter. Nanotubes can conduct electricity and may be useful as wires for connecting molecular devices together. Self-assembly: A process for putting together molecular
devices that relies on a molecule's natural attraction for a material or other molecules. Molecules designed to have certain chemical groups will connect themselves together without need for human control.
Rotaxanes: Organic molecules that consist of a
ring-shaped portion threaded on a dumbbell-shaped component. Can act as molecular switches as the ring slides back and forth.
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