KRAMERS-KRONIG CALCULATION OF THE GRAZING ANGLE REFLECTION SPECTRUM OF BARRIER OXIDE LAYER ON ALUMINUM

The nature of the grazing angle reflection spectrum of the thin oxide layer formed on the surface of aluminum was examined by Kramers-Kronig calculations. It was confirmed that the 960-cm-1 peak seen in the grazing angle reflection spectrum corresponds to the absorption band at 738 cm-1 of a low-temperature transition alumina such as gamma-Al2O3. The large frequency shift toward higher frequencies is explained in terms of the product between the real and imaginary parts of the refractive index of the oxide. Simulation using the Kramers-Kronig calculation showed, in addition, a very weak structure at about 700 cm-1 in the grazing angle reflection spectrum, which was attributed to a peak shifted from the 590-cm-1 absorption peak of gamma-Al2O3.