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 175-375degreesC and 225-350degreesC for the Ce(thd)(4) and Ce(thd)(3)phen(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 175-250degreesC for Ce(thd)(4) and 225-275degreesC for Ce(thd)(3)phen. The growth rates of CeO2 inside the ALD windows were 0.32 Angstrom (cycle)(-1) and 0.42 Angstrom (cycle)(-1) for Ce(thd)(4) and Ce(thd)(3) phen, 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.