Low Temperature Epitaxial Oxide Ultrathin Films and Nanostructures by Atomic Layer Deposition

Highly epitaxial and pure (001) CeO 2 ultrathin films have been prepared by atomic layer deposition (ALD) at 275 °C on Y-stabilized ZrO 2 cubic fluorite single crystal substrate using cerium β-diketonate (Ce(thd) 4 ) and ozone (O 3 ) as precursors. Substrate temperature and precursor pulses have been optimized to set the ALD window obtaining a growth per cycle of ≈0.2 Å/cycle. This extremely low growth rate has been identified as a key parameter to ensure epitaxial growth at these low temperatures. Post-thermal treatments at 900 °C in oxygen further improve ALD-CeO 2 film texture while maintaining film stoichiometry and ultrasmooth surface, rms < 0.4 nm. ALD-CeO 2 thin film growth has also been tested on perovskite single crystal substrates, SrTiO 3 and LaAlO 3, exhibiting CeO 2 epitaxial growth and thus validating ALD as an outstanding method for low temperature epitaxial growth. Furthermore, we demonstrate that by combining e-beam lithography and ALD it is feasible to obtain size-controlled CeO 2 nanostructures.