Morphological and structural control of nanostructured <100> oriented CeO2 films grown on random metallic substrates

Abstract

CeO₂ (cubic fluorite) thin films have been deposited on no-rolled Hastelloy C276 substrates by metal-organic chemical vapour deposition (MOCVD) from the Ce(hfa)₃·diglyme [Hhfa = 1,1,1,5,5,5-hexafluoro-2,4-pentanedione; diglyme = (CH₃O(CH₂CH₂O)₂CH₃)] precursor. The X-ray patterns of all samples grown in the 350–550 °C temperature range point to the formation of <100> oriented CeO₂ films, while at higher deposition temperatures (650–850 °C) random CeO₂ films are formed. XRD data indicate that 450 °C is the best deposition temperature. Detailed studies of the influence of all deposition parameters (precursor vaporization temperature, O₂ and Ar gas flows, deposition temperature and time) on the CeO₂ film growth have been carried out. There is evidence that the deposition process occurs in a mass transport regime. A suitable rationale for the observed textural changes vs. temperature has been proposed and the present columnar grain morphology, depending upon deposition temperatures, has been related to the zone model proposed by Mochvan and Demchishin for physical vapour deposition processes.