DFT study on the electronic structure and optical properties of an Au-deposited α-Fe₂O₃ (001) surface

The electronic structure and optical properties of gold clusters deposited on an α-Fe₂O₃ surface were studied by using density functional theory (DFT), with a special emphasis on the influence of Au cluster sizes. There is a strong interaction between Au clusters and the α-Fe₂O₃ surface, and the binding energy increases with an increase of Au cluster size. The Au atoms of the gold cluster are bonded to the iron atoms of the α-Fe₂O₃ surface for the Au/α-Fe₂O₃ system, and the electrons transfer from the Au cluster to the α-Fe₂O₃ surface with the largest number of electrons transferred for 4Au/α-Fe₂O₃. The peaks of the refractive index, extinction coefficient and dielectric function induced by Au clusters appear in the visible range, which results in the enhanced optical absorption for the Au/α-Fe₂O₃ system. The optical absorption intensifies with increasing Au cluster size in the visible range, showing a maximum value for 4Au/α-Fe₂O₃. Further increasing the Au cluster size above 4Au results in a decrease in absorption intensity. The results are in good agreement with those of the refractive index, extinction coefficient and dielectric function.