Abstract
We investigate the electronic structure and work function modulation of α-Fe2O3 films by strain based on the density functional method. We find that the band gap of clean α-Fe2O3 films is a function of the strain and is influenced significantly by the element termination on the surface. The px and py orbitals keep close to Fermi level and account for a pronounced narrowing band gap under compressive strain, while unoccupied dz2 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 pz 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 pz 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.
Highlights
Metals are protected from corrosion in many aqueous environments by the formation of “passive”oxide films that are typically only a few nanometers thick
These calculation results allow us to conclude that the electronic structure and work function of α-Fe2 O3 film could be modified by strain when the α-Fe2 O3 film is grown on a stainless steel (SS), which can be very useful for explaining the effect of strain, future experimental studies as well as fundamentally understand the corrosion behavior
The spin-density distributions of this system presented in Figure 1c, where the up- and down-spin densities are denoted by light yellow and green color, respectively, clearly indicating the AFM coupling along the c-direction
Summary
Metals are protected from corrosion in many aqueous environments by the formation of “passive”. Oxide films that are typically only a few nanometers thick. The transition metal oxides are an important class of functional materials [1] because of their localized d electrons [2,3,4]. The geometric, electronic, and magnetic properties [7,8,9]; carrier effective masses [10]; and other related properties on Fe2 O3 [11] were present in theoretical work. The technological importance of these films has led to widespread investigation of their structure, chemistry [12] and practical applications such as water splitting [13]. The atomic structure of α-Fe2 O3 is important to passivity, since this often controls its protective properties, where interfacial strain due Materials 2017, 10, 273; doi:10.3390/ma10030273 www.mdpi.com/journal/materials
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