Silicon crystal transistors are usually doped with phosphorous, boric or arsenic atoms to ensure optimum functionality. The depth and degree of doping are generated by ion implantation.

Ion implanters generally consist of a tube containing a high vacuum. They are positioned between a wafer and a source with phosphorous, boric or arsenic ions. These particles are accelerated under high voltages to approx. 500,000 V, causing them to penetrate the silicon to a depth of approx. 1 mm. The ion beam is generated by graphite electrodes, with graphite bafflers guiding and focusing the emitted ions. Graphite components coated with silicon carbide or pyrocarbon are best suited or this purpose. Despite their extremely good chemical resistance, continuous contact with the ion beam leads to wear, requiring their regular replacement.