Word: germanium
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Between the Atoms. In an ordinary electron tube, electrons "boil" off a heated filament into a high vacuum. There, unhampered by clogging air, they dance around obediently in response to electrical forces provided to act upon them. A transistor has no filament or vacuum, only a speck of hard germanium cut from a silvery crystal. But the mobile electrons are there, flashing through the empty channels between the ordered atoms of the crystal fragment...
...outer shell of its atom, germanium has four electrons. If the crystal were absolutely pure germanium, each of these electrons would be bound by a neighboring atom. But if an occasional atom of an impurity such as phosphorus, which has five outer electrons, is built into the crystal, one of its electrons is not bound, and so is free to move around. If the impurity is an element with only three outer electrons, there is a "hole" into which electrons from germanium can move under certain conditions. Every time an electron moves into one hole, a new hole is left...
SEAC is completely electronic, with no mechanical parts. Instead of the thousands of expensive and bulky vacuum tubes that serve as "brain cells" in other large computers, SEAC does most of its thinking with 12,800 germanium crystal diodes-modern descendants of the "crystals" in oldtime radios. The diodes are small, trouble-free and quick, allowing the electric pulses of the machine's thinking processes to circulate at the rate of one million per second...
...Transistor is a slim metal cylinder about an inch long. Inside are two hair-thin wires whose points press, two-thousandths of an inch apart, on a pinhead of germanium. A feeble current in the "input" wire controls a much larger current flowing from the "output" wire. Such "amplification" is the essential property of vacuum tubes. The Transistor works on a different principle (by changing the conductivity of the germanium), but it amplifies the input current as much as 100 times...