Polycrystalline silicon
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Polycrystalline silicon, or multicrystalline silicon, also called polysilicon, poly-Si, or mc-Si, is a high purity, polycrystalline form of silicon, used as a raw material by the solar photovoltaic and electronics industry.
Left side: solar cells made of polycrystalline silicon Right side: polysilicon rod (top) and chunks (bottom)
A rod of semiconductor-grade polysilicon
Polycrystalline silicon (used to produce silicon monocrystals by Czochralski process)
A picture of grain boundaries for polysilicon. Each grain is crystalline over the width of the grain. The grain boundary separates the grains where the adjoining grain is at a different orientation from its neighbor. The grain boundary separates regions of different crystal structure thus serving as a center for recombination. 'd' here is a characteristic grain size, which should be maximized for maximum solar cell efficiency. Typical values of d are about 1 micrometre.
Chemical vapor deposition
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Chemical vapor deposition (CVD) is a vacuum deposition method used to produce high-quality, and high-performance, solid materials. The process is often used in the semiconductor industry to produce thin films.
Free-standing single-crystal CVD diamond disc
Colorless gem cut from diamond grown by chemical vapor deposition