Abstract

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 °C from Y(thd)₃/O₃–Zr(thd)₄/O₃. Deposition temperatures were 310–365 °C for the Y(thd)₃/O₃–Cp₂Zr(CH₃)₂/O₃ and 275–350 °C for the Y(thd)₃/O₃–Cp₂ZrCl₂/O₃ precursor combinations. Growth rates with a Y to Zr pulsing ratio of 1 ∶ 1 were 0.56, 0.79 and 0.89 Å (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/O₃–Zr(thd)₄/O₃, showed the (111) preferred orientation. The lattice parameter was in the range of 5.09–5.28 Å 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.