Strain Effects in the Work Function and Charge Transfer of the Au(111) Surface

Work function (WF) is one of the most fundamental physical parameters of metal surfaces, which can not only reflect the electronic structure of metal surfaces but is also very sensitive to the surface microstructure. In this paper, we use first-principles calculations to systematically study the strain effects on the vacuum level, Fermi level, and WF of the Au(111) surface. We find that the vacuum level and Fermi level of the Au(111) surface increase under compressive strain and decrease under tensile strain, and the effects of biaxial strain on the vacuum level and Fermi level can be equivalent to the superposition of two perpendicular uniaxial strains. These strain effects are attributed to the charge transfer induced by the strain. However, the change of WF with strain is the result of the competition between the strain effects of the vacuum level and Fermi level. That leads to the WF increasing with compressive uniaxial strain and decreasing with tensile uniaxial strain. Moreover, because the Fermi level is more responsive to compressive uniaxial strain, the Fermi level changes faster than the vacuum level under compressive biaxial strain. Consequently, the WF decreases with increasing tensile biaxial strain and slightly increases before decreasing with increasing compressive biaxial strain.