Abstract

Zirconium oxide thin films have been deposited by atomic layer epitaxy (ALE) using Zr(thd)₄, Cp₂Zr(CH₃)₂ and Cp₂ZrCl₂ (thd = 3,3,5,5-tetramethylheptane-3,5-dionate, Cp = cyclopentadienyl) as zirconium precursors and ozone as the oxygen source. A plateau of constant growth rate (ALE window) was observed for the Zr(thd)₄/O₃ process at 375–400 °C, for Cp₂Zr(CH₃)₂/O₃ at 310–365 °C and for Cp₂ZrCl₂/O₃ at 275–350 °C. Within these temperature ranges constant deposition rates of 0.24, 0.55 and 0.53 Å (cycle)⁻¹ were obtained, respectively. Deposited films were characterised by XRD and AFM for crystallinity and surface morphology, while TOF-ERDA was used to analyse the ZrO₂ film stoichiometry and possible impurities. Films deposited by optimised parameters from Cp₂Zr(CH₃)₂/O₃ and Cp₂ZrCl₂/O₃ were crystalline showing the preferred (−111) orientation of monoclinic ZrO₂. In all films, the orthorhombic zirconia phase was also present, although at higher temperatures its relative amount decreased. Zr(thd)₄/O₃ process produced films with lowest crystallinity consisting of both orthorhombic and monoclinic phases. According to TOF-ERDA, films were nearly stoichiometric with less than 0.5 atom% hydrogen and carbon. Outside the ALE window, a small chlorine contamination (0.1–0.3 wt%) was observed by XRF when the ZrO₂ films were deposited from Cp₂ZrCl₂/O₃ at 200–275 °C.