Gigantic work function in layered AgF2 (This work is dedicated to Professor Michael K. Cyrański for his birthday.)

• Published in: Physical chemistry chemical physics : PCCP 2020-10, Vol.22 (38), p.21809-21815
• Main Authors: Wegner, Wojciech, Tokár, Kamil, Lorenzana, Jose, Derzsi, Mariana, Grochala, Wojciech
• Format: Article
• Language: English
• Subjects: Charge materials; Charge transfer; Chemical reactions; Diamonds; Electronic properties; Electronic structure; First principles; Insulators; Monolayers; Oxidizing agents; Reference systems; Superconductivity; Superconductor junctions; Superconductors; Work functions
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/d0cp03706k

AgF2 is a layered material and a correlated charge transfer insulator with an electronic structure very similar to the parent compounds of cuprate high-TC 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-TC superconductivity. As a first step in this direction, we studied the stability and properties of an isolated AgF2 monolayer.