Electronic Structure of Ce-doped ZrO₂Film: Study of DFT Calculation and Photoelectron Spectroscopy

Abstract

In this study, we evaluated the change of electronic structure during redox process in cerium-doped ZrO 2 grown by sol gel method. By sol-gel method, we could obtain cerium-doped ZrO 2 in high oxygen partial pressure and low temperature. After post annealing process in nitrogen ambient, the film is deoxidized. We used spectroscopic and theoretical methods to analysis change of electronic structure. X-ray absorption spectroscopy (XAS) for O K1-edge and Density Functional Theory (DFT) calculation using VASP code were performed to verify the electronic structure of the film. Also, high resolution x-ray photoelectron spectroscopy (HRXPS) for Ce 3d was carried out to confirm chemical bond of cerium doped ZrO 2 . Through the investigation of the electronic structure, we verified as followings.(1) During reduction process, binding energy of oxygen is increase. Simultaneously, oxidation state of cerium was change to 4+ to 3+. (2) Cerium 4+ and cerium 3+ states were generated at different energy level. (3) Absorption states in O K edge were mainly originated by Ce 4+ f 0 and Ce 3+, while occupied states in valance band were mainly originated from Ce 4+ f 2 .

Oxygen K-edge X-ray Absorption Spectra

“…The oxygen K-edge of ZrO 2 (Figure ) shows subtle differences between the different polymorphs. It mainly contains the 4d t 2g peak at 532.4 eV and the 4d e g peak at 535.5 eV, implying a crystal field of 3.1 eV. ,,− Several investigations of the oxygen K-edges in ZrO 2 and yttrium stabilized zirconia (YSZ) samples with varying compositions have been reported demonstrating that the spectra are very sensitive to local crystalline structure and dopant content. For example, ytrria stabilized zirconia ZrO 2 [Y] is an important ceramic material , used in dental crowns and nonmetal knife blades.…”

“…For example, ytrria stabilized zirconia ZrO 2 [Y] is an important ceramic material , used in dental crowns and nonmetal knife blades. Recently, a number of other dopants were studied in relation to the photocatalytic properties of ZrO 2 , including ZrO 2 [Ce] , and ZrO 2 [Cu] …”