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Silicon and Germanium In the late 1940s, two elements—silicon and germanium—suddenly received a surge in interest due to the discovery of their ability to act as "semiconductors," i.e., to conduct electricity more efficiently than an insulator (such as rubber) but less efficiently than a conductor (such as copper). The invention of the semiconductor device called the transistor in 1947 by John Bardeen, Walter H. Brattain, and William B. Shockley at the Bell Telephone Labora-

tories ushered in a revolution in electronics that continues today in the rapid advances in solid-state devices, integrated circuits, and miniaturized electronic components. Both silicon and germanium were recognized as elements long before their uses as semiconductors were even imagined. Silicon is the second most abundant element in the earth's crust (second only to oxygen), and is found in almost every rock, all natural water, plants, and animal skele-

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tons, as well as body tissues andfluids.It is never found in the free state, however, but most often as a compound with oxygen (SiO2) called silica; 95% of the earth's rocks contain silica as their principal component. Germanium, on the other hand, is a very rare element, comprising only about 0.0005% of the earth's crust; making recovery difficult, too, is the fact that germanium is not found in natural concentrations or deposits, but rather is evenly distributed in trace quantities in many rocks. Like silicon, germanium is never found in the free state, but always in various uncommon minerals and sulfide ores, especially those of silver, lead, tin, zinc, and antimony. Until the late 18th century, chemists were not able to separate elemental silicon from its silica compound; some chemists even considered silica itself to be a pure element. In 1787, A. Lavoisier in France speculated that silica was probably the oxide of an as-yet-undiscovered element. Various chemists attempted to isolate the element, including Sir Humphry Davy in England in 1800, and Louis Thenard and Joseph Gay-Lussa