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Material World
Element · Si

Silicon

The second most abundant element in the Earth's crust, and the substrate of essentially all modern electronics.

Semiconductor

Silicon makes up about a quarter of the Earth's crust by mass, almost all of it locked up in silicate minerals and silica. It is never found free in nature.

Its industrial significance comes from a narrow band of behaviour: silicon is a semiconductor, meaning its conductivity can be controlled by adding minute, precisely-placed impurities. That controllability, combined with the fact that its oxide is an excellent insulator that grows directly on the surface, is why silicon rather than any other semiconductor became the basis of the integrated circuit.

Extraction

Metallurgical-grade silicon is produced by reducing quartz with carbon in an electric arc furnace. Electronic use requires far greater purity, reached by converting the metal to a volatile chlorosilane, distilling it, and depositing purified silicon back out — the Siemens process. The result is measured in parts per billion of contaminant.

Uses

Two uses, at wildly different purities. The larger by mass is metallurgical: silicon is added to aluminium alloys to improve castability and to steel to deoxidise it, and silicon is the basis of silicone polymers used as sealants, lubricants and medical implants.

The larger by value is electronic. Semiconductor-grade silicon is refined to a purity of parts per billion, grown as single crystals and sliced into the wafers on which essentially all integrated circuits are built. Solar photovoltaics consume silicon at slightly lower purity and in far greater quantity, and dominate the world's installed generating capacity growth.

Medium confidence Weak evidence

How we know: checked recently · only one source, so there is nothing to cross-check it against · stated directly by the source.

How this connects

Where a connection has been confirmed by an outside reference, that reference is named beside it.

is found in

  • Quartz — mineral Wikidata
  • Silicon carbide — compound
  • Olivine — mineral
  • Amethyst — mineral variety Wikidata
  • Beta quartz — mineral · the silicon-oxygen framework is unbroken through the transition
  • Obsidian — rock · around seventy per cent as silica, the composition of a rhyolite — quenched before any crystal could form
  • Asbestos — material · the silicate framework, rolled into the fibres that made it useful and lethal at once
  • Optical fibre — material · as fused silica, and almost nothing else — the fibre is glass made pure by being assembled from a gas
  • Silicone rubber — material · alternating with oxygen in the backbone, and the reason the material is not organic chemistry at all
  • 6000 series aluminium alloy — alloy · 0.2–1.8% · the other half — neither element alone hardens the alloy, and together they do
  • Borosilicate glass — material · as silica, still the network former and about 80 per cent of it
  • Fused silica — material · and essentially nothing else — removing every other oxide is what the material is
  • Silicon nitride — compound · three per formula unit
  • Glass fibre — material · as silica, the network former
  • Mineral wool — material · as silicate, from the basalt or slag it was spun from
  • Polysilicon — material · to nine or eleven nines, which is a purity nothing else is produced at in bulk
  • Albite — mineral Wikidata
  • Anorthite — mineral Wikidata
  • Beryl — mineral Wikidata
  • Fayalite — mineral Wikidata
  • Forsterite — mineral Wikidata
  • Lepidolite — mineral · substitutes within a solid solution — an individual specimen may hold little of it
  • Microcline — mineral Wikidata
  • Muscovite — mineral Wikidata
  • Orthoclase — mineral Wikidata
  • Plagioclase — mineral
  • Pollucite — mineral Wikidata
  • Spodumene — mineral Wikidata
  • Talc — mineral PubChem
  • Topaz — mineral Wikidata
  • Zircon — mineral Wikidata

is sourced from

  • Quartz — mineral · reduced with carbon in an electric arc furnace
  • Sand — material · quartz sand reduced with carbon in an arc furnace, which is where the semiconductor industry, the photovoltaic industry and every silicone in a bathroom begin

is used in

  • Semiconductor manufacturing — industry
  • Electronics manufacture — industry · the substrate of essentially all of it, and it won not on being the best semiconductor but on forming a stable insulating native oxide
  • Transistor — object · the substrate, purified to around eleven nines — a purity nothing else is produced at in bulk
  • Smartphone — object · the processor, the memory and the image sensor — and the most energy-intensive manufactured material per gram there is

is used as

  • Lighting — application · as the substrate beneath most LED electronics, though not the emitter itself
  • Photovoltaics — application · crystalline silicon dominates, at slightly lower purity and far greater quantity than electronics needs

is an alternative to

  • Germanium — element · silicon displaced germanium in semiconductors within two decades — not for better semiconductor properties but because its oxide is a stable, insulating, easily grown film and germanium's is not
  • Silicon carbide — compound · in power electronics: silicon carbide holds off higher voltages and runs hotter, which is why an electric vehicle inverter increasingly uses it and a mains adapter does not
  • Gallium arsenide — compound · the perpetual challenger that has never seriously threatened it — silicon has a cheap native oxide, larger wafers and fifty years of investment, and gallium arsenide has the properties silicon lacks entirely
  • Battery graphite — material · the anode substitution everyone wants and nobody has: silicon stores an order of magnitude more lithium per gram and swells 300 per cent doing it, which cracks the particle — so the practical answer is a few per cent of silicon in a graphite anode rather than a replacement
  • Gallium nitride — compound · in power conversion: ten times the breakdown field means a tenth the thickness for the same voltage, which is why a modern charger is a third the size of the one before it

is produced by

  • Smelting — process · carbothermic reduction of silica with coke in a submerged arc furnace, which is smelting in the strict sense even though no ore is involved
  • Czochralski process — process · as the single-crystal wafer every integrated circuit is built on — the metallurgical grade that comes out of a furnace is the same substance and not remotely the same thing

is an input to

  • Czochralski process — process · charged to the crucible already refined; the process changes its arrangement and its purity, not its identity

is associated with

  • The semiconductor era — event · and it won not on being the best semiconductor but on forming a stable insulating native oxide

is a component of

  • Electrical steel — alloy · 2–3.5% · about three per cent, which roughly quadruples the resistivity and cuts eddy current loss — and stops at three and a half because more makes the sheet too brittle to roll

is a source for

  • Polysilicon — material · metallurgical-grade silicon at 98 or 99 per cent, which is fine for alloying and useless for anything electronic — the purification from there is the entire product

Sources

  • Material World
    Our own writing
  • Wikidata
    Wikimedia Foundation · Creative Commons CC0 1.0 Universal (public domain dedication)
  • PubChem
    US National Library of Medicine · Mixed — aggregated third-party content, rights retained by depositors

Questions this page answers

Where it comes from, and what it becomes

Follow Silicon back to what it starts as, and forward into what it becomes. Each step is a documented one — a real route material takes, not a chain of inference.

Upstream — what it comes from

  • Silicon → is produced by (carbothermic reduction of silica with coke in a submerged arc furnace, which is smelting in the strict sense even though no ore is involved) → Smelting → takes as input (as the element removed, not added) → Oxygen → is produced by (the largest output by tonnage, and the reason air separation units sit beside steelworks) → Air separation → takes as input (the feedstock, and an unusual one in being free, unlimited and available anywhere — the cost is entirely the energy to liquefy it) → Air
  • Silicon → is produced by (as the single-crystal wafer every integrated circuit is built on — the metallurgical grade that comes out of a furnace is the same substance and not remotely the same thing) → Czochralski process → takes as input (melted and pulled into the single crystal the wafers are sliced from — polysilicon is the feedstock, and the puller changes its arrangement rather than its purity) → Polysilicon → is produced by (the Siemens process: trichlorosilane distilled to purity, then decomposed onto heated silicon rods at 1,100 °C until they grow thick enough to break up) → Vapour deposition
  • Silicon → is sourced from (quartz sand reduced with carbon in an arc furnace, which is where the semiconductor industry, the photovoltaic industry and every silicone in a bathroom begin) → Sand → is sourced from (the ultimate source of most of it — granite weathers, the feldspar becomes clay and washes out, and the quartz survives as grains) → Granite → is composed of (by volume, alongside feldspar and lesser mica) → Quartz
  • Silicon → is sourced from (reduced with carbon in an electric arc furnace) → Quartz
  • Silicon → is produced by (carbothermic reduction of silica with coke in a submerged arc furnace, which is smelting in the strict sense even though no ore is involved) → Smelting → takes as input (roasted to drive off sulfur, then reduced to copper) → Chalcopyrite
  • Silicon → is produced by (carbothermic reduction of silica with coke in a submerged arc furnace, which is smelting in the strict sense even though no ore is involved) → Smelting → takes as input (reduced with carbon to metallic tin) → Cassiterite

These are the most distinct paths back. Silicon can be traced through others besides.

Downstream — what it becomes

  • Silicon → is a source for (metallurgical-grade silicon at 98 or 99 per cent, which is fine for alloying and useless for anything electronic — the purification from there is the entire product) → Polysilicon → is an input to (melted and pulled into the single crystal the wafers are sliced from — polysilicon is the feedstock, and the puller changes its arrangement rather than its purity) → Czochralski process → produces (grown as a boule and sliced, though it is harder to keep stoichiometric than silicon because the arsenic evaporates) → Gallium arsenide → is used in (radio-frequency and optoelectronic devices, where silicon's indirect band gap and lower carrier mobility are the limits) → Electronics manufacture → is associated with (and the supply chain it produced is the deepest and most concentrated in the world economy) → The semiconductor era complete chain
  • Silicon → is an input to (charged to the crucible already refined; the process changes its arrangement and its purity, not its identity) → Czochralski process → produces (grown as a boule and sliced, though it is harder to keep stoichiometric than silicon because the arsenic evaporates) → Gallium arsenide → is used in (radio-frequency and optoelectronic devices, where silicon's indirect band gap and lower carrier mobility are the limits) → Electronics manufacture → is associated with (and the supply chain it produced is the deepest and most concentrated in the world economy) → The semiconductor era complete chain
  • Silicon → is used in (the substrate, purified to around eleven nines — a purity nothing else is produced at in bulk) → Transistor → is used in (the component every other modern technology is assembled from, and one nobody ever sees) → Electronics manufacture → is associated with (and the supply chain it produced is the deepest and most concentrated in the world economy) → The semiconductor era complete chain
  • Silicon → is used in (the processor, the memory and the image sensor — and the most energy-intensive manufactured material per gram there is) → Smartphone → is used in (and it is where four separate raw-material arguments meet — the 3TG conflict minerals, cobalt, the rare earths, and everything too dispersed to recover) → Electronics manufacture → is associated with (and the supply chain it produced is the deepest and most concentrated in the world economy) → The semiconductor era complete chain
  • Silicon → is used in (the substrate of essentially all of it, and it won not on being the best semiconductor but on forming a stable insulating native oxide) → Electronics manufacture → is associated with (and the supply chain it produced is the deepest and most concentrated in the world economy) → The semiconductor era complete chain
  • Silicon → is associated with (and it won not on being the best semiconductor but on forming a stable insulating native oxide) → The semiconductor era complete chain

These are the most distinct paths onward. Silicon ends up in others besides.