Overview

Copper(I) oxide (KOPP-er one OK-side) is also known as cuprous oxide, red copper oxide, copper protoxide, copper hemioxide, and copper suboxide. It is a yellowish, red, or brown crystalline substance, depending on its method of preparation. It does not burn and is stable in dry air. In moist air, it slowly changes to copper(II) oxide (CuO). The compound has been used by humans for thousands of years, first as a pigment in glazes, and later in fungicides, electronic components, and industrial reactions.

In 1883, copper(I) oxide was the first substance found to have semiconducting properties. A semiconductor conducts an electric current, although not nearly as efficiently as a conductor like copper, gold, or silver. Semiconductor components are now widely used in computer chips, although they are now made from silicon rather than copper(I) oxide.

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