Gigantic work function in layered AgF2

Abstract

AgF₂ is a layered material and a correlated charge transfer insulator with an electronic structure very similar to the parent compounds of cuprate high-T_C superconductors. It is also interesting as it is a powerful oxidizer. Here we present a first principles computation of its electronic properties in a slab geometry including its work function for the (010) surface (7.76 eV) which appears to be the highest among known materials with non-dipolar surfaces, and surpassing even that of fluorinated diamond (7.24 eV). We demonstrate that AgF₂ will show a “broken-gap” type alignment becoming electron doped and promoting injection of holes in many wide band gap insulators if chemical reaction can be avoided. Novel junction devices involving p type and n type superconductors have been proposed. The issue of chemical reaction is discussed in connection with the possibility to create flat AgF₂ monolayers achieving high-T_C superconductivity. As a first step in this direction, we studied the stability and properties of an isolated AgF₂ monolayer.