Oxidation studies of aluminum thin films by Raman spectroscopy

Raman spectroscopy has been used for the study of the oxidation of pure thin aluminum films in air. The films were annealed at 303, 423, 573, 673 and 773 K. The spectra were analysed in the range 230–900 cm −1 and the changes observed have been correlated with different stages of oxidation induced by heating. During the initial stages of oxidation and at low temperatures, amorphous γ-Al 2O 3 is formed on the surface. The shifts in frequencies and the overlapping of bands observed in the temperature range 303–423 K may be due to the transformation of the amorphous γ-Al 2O 3 into a quasi-crystalline form. From 423 to 673 K the natures of the bands are almost the same. From 673 to 773 K the disappearance of certain bands may be attributed to the increase in octahedral coordination of Al 3+, ions resulting in more structurally ordered γ-Al 2O 3.