Structure and spectroscopic ellipsometry studies of nanocrystalline Dy2O3 thin films deposited on Al2O3 wafers by electron beam evaporation technique

This work investigates the effect of film thickness on the optical properties of dysprosium oxide (Dy 2 O 3 ), fabricated onto sapphire (Al 2 O 3 ) substrates using electron beam evaporation. The grazing incidence X-ray diffraction (GI-XRD) analysis showed that all films have a cubic crystalline structure. The average crystallite size was calculated using the Debye–Scherrer equation and was found to increase with the increasing film thickness. Similar behavior was observed in scanning electron microscopy and atomic force microscopy images. The optical properties of the grown layers such as the refractive index (n), extinction coefficient (k), and optical allowed f–f transitions of Dy 3+ were analyzed using spectroscopic ellipsometry (SE). The allowed f–f transitions of Dy 3+ was found to increase from 2.35 eV to 2.50 eV by decreasing the film thickness from 10 nm to 5 nm. UV–Vis spectrophotometry was used to examine the reflectance of Dy 2 O 3 thin films. The results obtained in this study indicated that Dy 2 O 3 with a 5 nm thickness is a better choice to grow an improved anti-reflective layer compared with the 10 nm layer.