Semiconductor device
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A semiconductor device is an electronic component that relies on the electronic properties of a semiconductor material for its function. Its conductivity lies between conductors and insulators. Semiconductor devices have replaced vacuum tubes in most applications. They conduct electric current in the solid state, rather than as free electrons across a vacuum or as free electrons and ions through an ionized gas.
NASA's Glenn Research Center clean room
A stylized replica of the first transistor
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.