Strain Effect on Electronic Structure and Work Function in α-Fe(2)O(3) Films

We investigate the electronic structure and work function modulation of α-Fe(2)O(3) films by strain based on the density functional method. We find that the band gap of clean α-Fe(2)O(3) films is a function of the strain and is influenced significantly by the element termination on the surface. The p(x) and p(y) orbitals keep close to Fermi level and account for a pronounced narrowing band gap under compressive strain, while unoccupied d(z)(2) orbitals from conduction band minimum draw nearer to Fermi level and are responsible for the pronounced narrowing band gap under tensile strain. The spin polarized surface state, arising from localized dangling-bond states, is insensitive to strain, while the bulk band, especially for p(z) orbital, arising from extended Bloch states, is very sensitive to strain, which plays an important role for work function decreasing (increasing) under compressive (tensile) strain in Fe termination films. In particular, the work function in O terminated films is insensitive to strain because p(z) orbitals are less sensitive to strain than that of Fe termination films. Our findings confirm that the strain is an effective means to manipulate electronic structures and corrosion potential.