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Single-crystal (or monocrystalline) silicon is the base material of the electronic industry. It consists of silicon in which the crystal lattice of the entire solid is continuous and unbroken to its edges, with no grain boundaries. It may be intrinsic, i.e. composed of exceedingly pure silicon alone, or doped, containing very small quantities of other elements added to change in a controlled manner its electronic properties. Most silicon monocrystals are grown by the Czochralski process, in the shape of cylinders up to 2 m long and 30 cm in diameter.

Single-crystal silicon is perhaps the most important technological material of the last decades (the "silicon era"), because its availability at an affordable cost has been essential for the fabrication of the electronic devices on which the present day electronic and informatic revolution is based.

The single-crystal form is used in the semiconductor device fabrication since grain boundaries would bring discontinuities and favor imperfections in the microstructure of silicon, such as impurities and crystallographic defects, which can have significant effects on the local electronic properties of the material. On the scale that devices operate on, these imperfections would have a significant impact on the functionality and reliability of the devices. Without the crystalline perfection, it would be virtually impossible to build VLSI devices, in which millions (billions, today ) of transistor-based circuits (all of which must reliably work) are combined into a single chip to get e.g. a microprocessor. Therefore, electronic industry has invested heavily in facilities to produce large single crystals of silicon.

Single crystal is opposed to amorphous silicon, in which the atomic order is limited to short range order only. In between the two extremes there is polycrystalline silicon, which is made up of small crystals, known as crystallites.

Monocrystalline silicon is also used in the manufacturing of high performance solar cells. Since, however, solar cells are less demanding than microelecronics for as concerns structural imperfections, today single crystal is often replaced by the cheaper polycrystalline silicon.