Formation and stability of lanthanum oxide thin ®lms deposited from b-diketonate precursor

Lanthanum oxide thin ®lm deposition by atomic layer epitaxy (ALE) was studied at 180±4258C on soda-lime glass and Si(1 0 0) substrates using a b-diketonate type precursor La(thd)3 and ozone. The chemical constituents of the ®lms were analyzed by TOF-ERDA, RBS and FTIR while XRD and AFM were used to determine the crystallinity and surface morphology. Films grown below 2758C were amorphous La2O2CO3, while at deposition temperatures above 3008C XRD patterns indicated that cubic La2O3 phase was formed. All the ®lms were transparent and uniform with only small thickness variations. Carbonate type impurity was found in all ®lms, but the carbon content of the ®lms decreased with growth temperature being 3 at.% in ®lms grown above 4008C. Hexagonal La2O3 was obtained when the ®lms grown on silicon substrates were annealed at 8008C or above in a nitrogen ¯ow. The as-deposited cubic and annealed hexagonal La2O3 ®lms were found to be chemically unstable in ambient air since a transformation to monoclinic LaO(OH) and hexagonal La(OH)3 was detected, respectively. # 2001 Elsevier Science B.V. All rights reserved.