Silicon

Silicon is a metalloid whose chemistry lies between that of metals and nonmetals. Its standard atomic weight is about 28.085, and its solid form has a diamond-cubic crystal structure closely related to that of carbon. Pure silicon is relatively unreactive at ordinary temperatures, but it reacts with halogens and strong bases; a thin surface layer of silicon dioxide helps protect it from further oxidation.¹

Most terrestrial silicon is locked into silicate minerals, compounds built from silicon–oxygen tetrahedra, or into silica, SiO₂. Feldspars, pyroxenes, micas, and quartz are major examples. Silicon is the second-most abundant element in Earth’s crust by mass after oxygen, although it is not found naturally as a significant native metal.

Silicon was isolated in recognizable elemental form in the nineteenth century, after earlier experiments had produced impure silicon-containing material. Jöns Jacob Berzelius is generally credited with preparing relatively pure silicon in 1824 by reducing a fluoride compound with potassium; the name derives from Latin silex, meaning flint.¹

Industrial silicon is produced chiefly by carbothermic reduction of quartz or other silica in electric arc furnaces. The resulting metallurgical-grade material is refined further when high purity is required. Semiconductor manufacturing uses processes such as chemical purification, crystal growth, wafer slicing, and zone refining to reduce impurities to extremely low concentrations; the Czochralski process is widely used to grow large single crystals.² Silicon alloys, especially ferrosilicon, also consume substantial quantities in iron and steel production.

Silicon’s most consequential property is its controllable semiconductor behavior. Its electrical conductivity increases when atoms such as boron or phosphorus are introduced in carefully measured amounts, creating p-type and n-type material. Joining these regions produces devices including diodes, transistors, integrated circuits, sensors, and power electronics.³

The element transformed computing because silicon dioxide forms a stable, useful insulating layer on silicon, enabling the planar fabrication methods used for densely packed circuits. Silicon is also the dominant material in conventional crystalline-silicon photovoltaic cells, where absorbed light generates charge carriers that can be collected as electric current. Outside electronics, silicon compounds appear in glass, ceramics, cement, silicones, sealants, and medical and industrial materials.

Silicon has important biological and environmental dimensions beyond electronics. Dissolved silicic acid is taken up by diatoms, grasses, and some other organisms; diatoms use it to build intricate silica shells, while silicon deposition can strengthen plants and influence their interactions with herbivores.⁴

Elemental silicon should also be distinguished from crystalline silica dust. Cutting, crushing, or drilling stone, concrete, and engineered materials can release respirable particles that cause silicosis, lung cancer, chronic obstructive pulmonary disease, and kidney disease; occupational controls therefore focus on dust suppression, ventilation, and respiratory protection.⁵ Another less obvious edge case is silicon’s role in metallurgy: small additions can improve cast iron and aluminum alloys, while ferrosilicon acts as a deoxidizer and alloying material in steelmaking. These uses rely on different grades and forms than those required for microelectronics.

Metalloid

An element with a mixture of metallic and nonmetallic properties; silicon is a standard example.

Silica

Silicon dioxide, SiO2, found naturally in minerals such as quartz and used in glass and ceramics.

Silicate

A mineral or compound containing silicon–oxygen structural units, commonly forming the principal minerals of Earth’s crust.

Doping

The deliberate introduction of small amounts of impurity atoms to control a semiconductor’s electrical behavior.

Silicone

A family of synthetic silicon–oxygen polymers with organic groups; silicone is chemically distinct from elemental silicon.