Combination of characterization techniques for atomic layer deposition MoO 3 coatings: From the amorphous to the orthorhombic α-MoO 3 crystalline phase

• Published in: Journal of vacuum science & technology. A, Vacuum, surfaces, and films Vacuum, surfaces, and films, 2011-09, Vol.30 (1), p.01A107-01A107-6
• Main Authors: Diskus, Madeleine, Nilsen, Ola, Fjellvåg, Helmer, Diplas, Spyros, Beato, Pablo, Harvey, Clare, van Schrojenstein Lantman, Evelien, Weckhuysen, Bert M.
• Format: Article
• ISSN: 0734-2101; 1520-8559
• DOI: 10.1116/1.3643350

Thin films of MoO 3 deposited on Si(111) and Al 2 O 3 (001) substrates by atomic layer deposition have been investigated by x-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and Raman spectroscopy for detailed characterization of composition and morphology. Comparison of angle resolved x-ray photoelectron spectroscopy (ARXPS) and XPS depth profiles based on Ar + sputtering is reported. Sputtering induces a reduction of molybdenum in MoO 3 from +IV to metallic Mo as the interface toward Si is approached, whereas ARXPS on a 10 nm thin film shows that Mo(VI) remains outside the interface toward Si where lower valent molybdenum compounds are formed. Upon annealing, the as-deposited amorphous thin films of MoO 3 crystallize into β- or α-MoO 3 as identified by x-ray diffraction. The current study provides a convenient route toward formation of metastable β-MoO 3 and a full crystallization pathway from amorphous to crystalline α-MoO 3 . Combined AFM and Raman analysis have been performed on thin films of α-MoO 3 deposited on Al 2 O 3 (001) and prove that the crystallization proceeds via island growth at 600 °C. The Raman intensity ratios between different bands depend strongly on morphology and size of crystalites.