Ionization enhancement of zirconium atoms in inductively coupled discharge

This paper reports on ionization of sputtered zirconium (Zr) atoms in inductively coupled argon discharge. A Zr+ ion flux fraction to overall Zr species mainly was obtained by deposition measurements with the retarding bias method, and the fraction approximately reached ∼100%. The Zr+ ion fraction was affected by the discharge pressure, and hardly dependent on the discharge power corresponding to an electron density. This result suggested that the Zr+ ions were generated with ionization process other than electron impact such as Penning effect. There was an optimal pressure to produce the Zr+ ions, and the Zr+ ion density estimated from the deposition measurement was consistent with that obtained from a combination of Langmuir probe measurements and mass spectroscopic measurements.