Effect of Cr-doping on the electronic structure and work function of α-Fe2O3 thin films

Xiaolong Li; Li Chen; Hongmei Liu; Zhishan Mi; Changmin Shi; Lijie Qiao

doi:10.1039/c7cp02472j

Effect of Cr-doping on the electronic structure and work function of α-Fe₂O₃ thin films

Phys Chem Chem Phys. 2017 Oct 4;19(38):26248-26254. doi: 10.1039/c7cp02472j.

Authors

Xiaolong Li¹, Li Chen, Hongmei Liu, Zhishan Mi, Changmin Shi, Lijie Qiao

Affiliation

¹ Corrosion and Protection Center, Key Laboratory for Environmental Fracture (MOE), University of Science and Technology Beijing, Beijing 100083, People's Republic of China. lqiao@ustb.edu.cn.

PMID: 28932834
DOI: 10.1039/c7cp02472j

Abstract

We investigate the effect of Cr-doping on the properties of α-Fe₂O₃(001) thin films with Fe termination using the local density approximation plus a Hubbard U correction. We find that both the doping site and concentration of Cr atoms dramatically affect the electronic structure and work function (W_F) of α-Fe₂O₃ films. The results demonstrate that it is most energetically favorable for Cr atoms to substitute the Fe atoms in the sub-surface of α-Fe₂O₃ thin films. The doping of Cr atoms in the sub-surface not only lowers the band gap of the film but also greatly enhances the work function by 0.9 eV with respect to the pure α-Fe₂O₃ film. The increase of W_F correlates with the reduction of occupied O p_x/p_y states at the top valence band which leads to a decrease of the Fermi energy. As the Cr concentration changes from 4.2% to 16.7%, the W_F firstly increases, and then drops. The W_F reaches a maximum of 6.61 eV for the Cr concentration of 8.3%. These results suggest that doping Cr atoms in a α-Fe₂O₃(001) thin film can increase the corrosion potential and benefits the protection of steel from corrosion.