Polysilicon

Polycrystalline silicon or polysilicon or poly-Si or simply poly (in context) is a material consisting of multiple small silicon crystals.Polycrystalline silicon can be one of the purest elements in the world; it may be as much as 99.9999999+% pure. After air and water, silicon is the most important non-carbon (inorganic) substance in the world. Silicon is most often companioned with oxygen to form sand -- silicon dioxide. When the oxygen is stripped from the silicon, crude polycrystalline silicon remains. Ultra pure poly is used in the semiconductor industry. To purify the crude poly, chemical plants that look like petrochemical oil refineries are required. The final step in manufacturing semiconductor grade poly is to grow poly rods that are five to eight feet in length.
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silicion with randonly oriented grains where each grain is made up of single crystalline materail.