Deposition of yttria-stabilized zirconia thin films by atomic layer epitaxy from beta-diketonate and organometallic precursors

Yttria-stabilised zirconia (YSZ) films were deposited by atomic layer epitaxy (ALE) using Zr(thd)(4), Cp2Zr(CH3)(2) and Cp2ZrCl2 as zirconium precursors. Y(thd)(3) and ozone were used as yttrium and oxygen sources, respectively. YSZ films were grown at 375 degreesC from Y(thd)(3)/O-3-Zr( thd)(4)/O-3. Deposition temperatures were 310-365 degreesC for the Y(thd)(3)/O-3-Cp2Zr(CH3)(2)/O-3 and 275-350 degreesC for the Y(thd)(3)/O-3-Cp2ZrCl2/O-3 precursor combinations. Growth rates with a Y to Zr pulsing ratio of 1 : 1 were 0.56, 0.79 and 0.89 Angstrom (cycle)(-1) when Zr(thd)(4),Cp2Zr(CH3)(2) and Cp2ZrCl2 were used as zirconium precursors, respectively. Crystallinity and surface morphology of the deposited films were characterised by XRD and AFM while TOF-ERDA, XRF and SEM-EDX were used to analyse stoichiometry and possible impurities. The YSZ films were (100) oriented when deposited with a Y to Zr pulsing ratio of 1 : 1. Only thinner films ( <60 nm), deposited from Y(thd)(3)/O-3-Zr(thd)(4)/O-3, showed the (111) preferred orientation. The lattice parameter was in the range of 5.09-5.28 angstrom when the Y2O3 content was 5-89 mol%. When Cp2ZrCl2 was used as zirconium precursor, 0.1-1.7 mol% chlorine was observed in the films. According to the AFM analysis, roughness was dependent on the pulsing ratio of the Y and Zr precursors.