<P> Polycrystalline and paracrystalline phases are composed of a number of smaller crystals or crystallites . Polycrystalline silicon (or semi-crystalline silicon, polysilicon, poly - Si, or simply "poly") is a material consisting of multiple small silicon crystals . Polycrystalline cells can be recognized by a visible grain, a "metal flake effect". Semiconductor grade (also solar grade) polycrystalline silicon is converted to "single crystal" silicon--meaning that the randomly associated crystallites of silicon in "polycrystalline silicon" are converted to a large "single" crystal . Single crystal silicon is used to manufacture most Si - based microelectronic devices . Polycrystalline silicon can be as much as 99.9999% pure . Ultra-pure poly is used in the semiconductor industry, starting from poly rods that are two to three meters in length . In microelectronic industry (semiconductor industry), poly is used both at the macro-scale and micro-scale (component) level . Single crystals are grown using the Czochralski process, float - zone and Bridgman techniques . </P> <Table> <Tr> <Td> </Td> <Td> This section does not cite any sources . Please help improve this section by adding citations to reliable sources . Unsourced material may be challenged and removed . (January 2014) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This section does not cite any sources . Please help improve this section by adding citations to reliable sources . Unsourced material may be challenged and removed . (January 2014) (Learn how and when to remove this template message) </Td> </Tr> <P> At the component level, polysilicon has long been used as the conducting gate material in MOSFET and CMOS processing technologies . For these technologies it is deposited using low - pressure chemical - vapour deposition (LPCVD) reactors at high temperatures and is usually heavily doped n - type or p - type . </P>

Where does the silicon in solar panels come from