On the specific behavior of the work function and surface potential of an asymmetric metal-dielectric nanosandwich

Abstract

We examine thin film on a dielectric substrate (vacuum/Al/SiO2) in the stabilized jellium model and the Kohn–Sham method. We investigate surface and size effects on the effective potential and the electron work function, and analyze the spatial distributions of electrons and potentials. It is found that a dielectric environment generally leads to a decrease in the work function. The effect of dielectric confinement for the electron work function of the asymmetric metal-dielectric nanosandwiches is reduced only by the surface area weighted average value of the dielectric constants. This conclusion follows from the application of the Gauss theorem for a conducting sphere with an inhomogeneous dielectric coating. The flow of electrons from the dielectric face to the vacuum one due to the contact potential difference manifests itself in the appearance of an additional dipole between the left and right face within the spatial distributions of ions. This leads to the fact that in a vacuum the electrostatic and effective potentials change sign twice, as a result of which a potential barrier appears above the vacuum level. We introduced the position of an electron conduction band in the dielectric as the input parameter in the self-consistency procedure for one of the sandwich approximations. As it turned out, the barrier height depends only on the used local or non-local approximation of the exchange-correlation energy. The nontrivial origin and behavior of the calculated effective potential on the vacuum side of the film, as well as the reasons for it, are discussed.