Self-sputtering far above the runaway threshold: an extraordinary metal-ion generator.

When self-sputtering is driven far above the runaway threshold voltage, energetic electrons are made available to produce "excess plasma" far from the magnetron target. Ionization balance considerations show that the secondary electrons deliver the necessary energy to the "remote" zone. Thereby, such a system can be an extraordinarily prolific generator of usable metal ions. Contrary to other known sources, the ion current to a substrate can exceed the discharge current. For gasless self-sputtering of copper, the usable ion current scales exponentially with the discharge voltage.