Asimov's New Guide to Science by Isaac Asimov

Author:Isaac Asimov [Asimov, Isaac]
Format: epub
Tags: Science, History
Published: 0101-01-01T00:00:00+00:00

In 1948, William Bradford Shockley, Walter Houser Brattain, and John Bardeen at the Bell Lab went on to produce a transistor that could act as an amplifier. This was a germanium crystal with a thin p-type section sandwiched between two n-type ends. It was in effect a triode with the equivalent of a grid between the filament and the plate. With control of the positive charge in the p-type center, holes could be sent across the junctions in such a manner as to control the electron flow. Furthermore, a small variation in the current of the p-type center would cause a large variation in the current across the semiconductor system. The semiconductor triode could thus serve as an amplifier, just as a vacuum tube triode did. Shockley and his co-workers Brattain and Bardeen received the Nobel Prize in physics in 1956.

However well transistors might work in theory, their use in practice required certain concomitant advances in technology—as is invariably true in applied science. Efficiency in transistors depended very strongly on the use of materials of extremely high purity, so that the nature and concentration of deliberately added impurities could be carefully controlled.

Fortunately, William Gardner Pfann introduced the technique of zone refining in 1952. A rod of, let us say, germanium, is placed in the hollow of a circular heating element, which softens and begins to melt a section of the rod. The rod is drawn through the hollow so that the molten zone moves along it. The impurities in the rod tend to remain in the molten zone and are therefore literally washed to the ends of the rod. After a few passes of this sort, the main body of the germanium rod is unprecedentedly pure.

By 1953, tiny transistors were being used in hearing aids, making them so small that they could be fitted inside the ear. In short order, the transistor steadily developed so that it could handle higher frequencies, withstand higher temperatures, and be made ever smaller. Eventually it grew so small that individual transistors were not used. Instead, small chips of silicon were etched microscopically to form integrated circuits that would do what large numbers of tubes would do. In the 1970s, these chips were small enough to be thought of as microchips.

Such tiny solid-state devices that are now universally used offer perhaps the most astonishing revolution of all the scientific revolutions that have taken place in human history. They have made small radios possible; they have made it possible to squeeze enormous abilities into satellites and probes; most of all, they have made possible the development of ever-smaller and ever-cheaper and ever-more versatile computers and, in the 1980s, robots as well. The last two items will be discussed later in chapter 17.

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