Plasma diagnostics and deposition of functional zirconia thin films by reactive magnetron sputtering

A magnetron discharge with a zirconium cathode is operated in an argon/oxygen gas mixture. The magnetron is operated in pulsed mode with repetition frequencies of 0.5-5 kHz and in radiofrequency mode. Positively charged atomic O+, Ar+, and Zr+ and molecular O2+, ArO+, Ar2+, ZrO+, and ZrO2+ are observed. Negatively charged O- ions sputtered from the magnetron’s cathode are investigated in some detail. The intensity of negatively charged O- is strongly influenced by the repetition rate. Formation of excited Ar, Ar+, Zr, and Zr+ species is influenced by target poisoning. Target poisoning reduces the deposition rate by about one order of magnitude.

Zirconium dioxide films are either deposited at room temperature followed by post-deposition annealing or on heated Si substrates. Deposited films are characterised by means of x-ray diffractometry, Raman spectroscopy, Fourier transform infrared spectroscopy, infrared ellipsometry, and spectroscopic optical ellipsometry. XRD confirms the monoclinic lattice phase of the films. The ultra-wide bandgap of the deposited zirconia films is confirmed by spectroscopic ellipsometry measurements. Two direct optical bandgaps at about 5.25 eV and 6.1 eV are extracted from the measurements.