Cerium dioxide buffer layers at low temperature by atomic layer deposition

Thin films of cerium dioxide were deposited by atomic layer deposition (ALD). Temperature ranges studied in detail were 175–375 °C and 225–350 °C for the Ce(thd)4 and Ce(thd)3phen (thd = 2,2,6,6-tetramethyl-3,5-heptanedionate, phen = 1,10-phenanthroline) precursors, respectively. Ozone was used in both cases as oxygen source. Thickness, crystallinity and morphology of the CeO2 films were determined by UV-VIS spectroscopic, XRD and AFM measurements, respectively. Narrow ALD windows, i.e. temperature ranges with constant growth rate, were observed at temperatures 175–250 °C for Ce(thd)4 and 225–275 °C for Ce(thd)3phen. The growth rates of CeO2 inside the ALD windows were 0.32 Å (cycle)−1 and 0.42 Å (cycle)−1 for Ce(thd)4 and Ce(thd)3phen, respectively. CeO2 films grown on soda lime glass and Si(100) were polycrystalline and slightly oriented with the (200) and (111) peaks as the strongest reflections. TOF-ERD analysis of the Ce∶O ratio showed that the films were nearly stoichiometric but that they contained hydrogen (7–10 atom%), as well as some carbon and fluorine, as impurities.