of vacuum tubes and relays in communication systems. Various approaches to the problem were examined and abandoned. The search narrowed eventually to solid materials, where a few scientists settled on a hunch that the answer lay in semiconductors. To move from the hunch to the transistor, however, required intensive basic research on the behavior of semiconducting materials. It required also the semiempirical development of zone refining and other techniques to make virtually perfect single crystals of silicon of unprecedented purity.
This close linkage of knowledge to function is characteristic of the achievements of materials science and engineering. Selected examples appear in Table 2. A second characteristic of the field is that the initiative for new materials developments, and for the attendant basic research, springs most often from a practical problem, however dimly perceived. It is true that fundamental work on materials has turned up unexpected, momentous discoveries, such as high-field super-conductors. But more frequently, the basic studies have been stimulated by a discovery or invention whose exploitation required greatly expanded fundamental research. Thus the tunnel diode and the laser largely preceded and spurred the extensive basic work on the tunnel and laser effects in materials.
The bodies of knowledge required for progress in materials, and particularly for solving complex technological problems, often do not coincide with those of the traditional disciplines. Materials science and engineering, as a result, has come to embrace a number of traditional disciplines and segments of disciplines (Figure 7), and