Characterization of plume fluence for laser ablation of yttria stabilized zirconia in mixed oxygen and argon environments

Abstract

Pulsed laser deposition (PLD) is a versatile and efficient deposition technique that produces a highly energetic plume, from which films are grown. The plume characteristics are highly dependent on background environment conditions, with low pressure oxygen being the most common choice for the deposition of highly oriented yttria stabilized zirconia (YSZ) films. Emission intensity measurements of the plume excited and ionized species were made using four different narrow band filters in conjunction with a high-speed photomultiplier tube and digital oscilloscope. Experiments were performed with five background gas compositions containing oxygen and argon, at seven different pressures ranging from 0.3 Pa to 26.7 Pa. For Ar/O 2 gas mixtures, there was an optimum background pressure of 1–10 Pa, providing a highest level of plasma ionization and excitation. Plume species were also considerably decelerated through gas collisions at pressures above 1 Pa. For films grown at approximately 1 Pa pressure, the variation of Ar/O 2 background gas compositions had a minor effect on YSZ crystal size and lattice parameters. Film crystallinity was drastically improved, when negative bias was applied to the substrate. This was explained by the presence of Zr ions in the plume, which accelerate with negative bias to provide surface ion bombardment and structure reconstruction.