and designers in all fields, and one that can greatly expand the potential for performance of materials.

In many instances, materials processing is a critical step in the development of an entire technology. Electronics is an outstanding example of an industry that depended from its beginning on the invention of processing techniques—in this case, the growth and purification of semiconductor crystals. In other instances, new materials processing techniques may lead to materials sub-stitutions in existing technologies with striking improvements in performance and reductions in cost. Examples of the latter situation are the substitution of optical glass fiber for copper wire in long-distance communication systems and the replacement of some metallic components in aircraft and automobiles by composite materials. In all cases, materials processing draws upon the results of research and design and also relies upon empirical investigations and extensive testing programs.

Semiconductors

The birth and rapid growth of the electronics and computer industries required an extensive series of interacting developments in basic research, materials processing, and design. An early and key step was the invention of the transistor in the late 1940s. This has been celebrated, and justly so, as a triumph of basic research. The enabling fundamental studies were strongly knowledge driven, although they were carried out in the context of a search for radically new communications technologies. In the course of the basic studies, both experimental and theoretical, wholly new patterns of electronic behavior were discovered and interpreted.

The invention of the transistor was the first step, albeit the most important, in a long series of discoveries and technical developments that were necessary to transform the discovery of electronic amplification in solids into the modern electronics and computer industries. Many of those still dynamic and evolving technologies are materials processing techniques that were developed specifically to exploit the new scientific discoveries for practical purposes. These were application- or market-driven developments, in contrast to the invention of the transistor, which was knowledge driven.

An excellent example of application-driven research is the development of the zone refining method for purifying silicon, which followed shortly after the invention of the transistor. This research was application driven in the sense that silicon and germanium semiconductors required impurity levels that were far below those obtainable by existing technologies at that time. In zone refining, purification is achieved by the passage of a thin molten zone, which removes the impurities, through the otherwise solid material. This invention was essential to the successful production of homogeneous high-purity crystals at reasonable cost.



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