Silicon

(L. silex, silicis, flint) Davy in 1800 thought silica to be a compound and not anelement; later in 1811, Gay Lussac and Thenard probably prepared impure amorphous siliconby heating potassium with silicon tetrafluoride.

In 1824 Berzelius, generally credited with the discovery, prepared amorphous silicon bythe same general method and purified the product by removing the fluosilicates by repeatedwashings. Deville in 1854 first prepared crystalline silicon, the second allotropic formof the element.

Silicon is present in the sun and stars and is a principal component of a class ofmeteorites known as aerolites. It is also a component of tektites, a natural glassof uncertain origin.

Silicon makes up 25.7% of the earth's crust, by weight, and is the second most abundantelement, being exceeded only by oxygen. Silicon isnot found free in nature, but occurs chiefly as the oxide and as silicates. Sand, quartz,rock crystal, amethyst, agate, flint, jasper, and opal are some of the forms in which theoxide appears. Granite, hornblende, asbestos, feldspar, clay, mica, etc. are but a few ofthe numerous silicate minerals.

Silicon is prepared commercially by heating silica and carbon in an electric furnace,using carbon electrodes. Several other methods can be used for preparing the element.Amorphous silicon can be prepared as a brown powder, which can be easily melted orvaporized. The Czochralski process is commonly used to produce single crystals of siliconused for solid-state or semiconductor devices. Hyperpure silicon can be prepared by thethermal decomposition of ultra-pure trichlorosilane in a hydrogen atmosphere, and by avacuum float zone process.