Spectroscopic ellipsometry study of Mn doped CeO2 thin films prepared by radio-frequency magnetron sputtering

Abstract

Mn doped CeO2 (Ce1-xMnxO2, x=0, 0.03, 0.06) thin films were deposited on Si (100) substrates by radio-frequency magnetron sputtering. X-ray diffraction and Raman analysis indicates that the films are cubic fluorite crystal structure with a preferred orientation along (111), which is the same as that of pure CeO2. Atomic force microscopy reveals that the film surface morphology is dependent on the Mn doped content. The influence of Mn doped content on the optical properties was studied by spectroscopic ellipsometry (SE) in the UV-NIR region (210∼2500 nm). The energy dispersion optical constants (the refractive index n and the extinction coefficient k) of Ce1-xMnxO2 thin films were obtained by analyzing the SE spectra. Under the assumption of a direct band-to-band transition, the optical band gap energies Eg for these films were determined. The values of n, k and Eg are functions of the Mn doped contents. The results showed that the Eg values of the Ce1-xMnxO2 thin films are 3.22, 3.32 and 3.35 eV, and the n values at wavelength of 632 nm are about 2.29, 2.38 and 2.49 for Mn doped content x=0, 0.03 and 0.06, respectively. The values of n and Eg increases linearly with increasing Mn doped content.