SINGLE CRYSTAL

any solid object in which an orderly three-dimensional arrangement of the atoms, ions, or molecules is repeated throughout the entire volume. Certain minerals, such as quartz and the gemstones, often occur as single crystals; synthetic single crystals of elements, especially silicon and germanium, are used in solid-state electronic devices such as transistors, rectifiers, and integrated circuits. In the preparation of synthetic single crystals, special techniques are employed to control the deposition of material upon one nucleus (see nucleation), which often is a small single crystal of the substance obtained from a previous preparation.