Layered semiconducting electrides in p-block metal oxides

TL;DR

This paper introduces a new class of p-block metal-based semiconducting electrides in bilayer SnO and PbO, featuring bipolar electride states with high carrier mobility and potential for p-type semiconductor applications.

Contribution

It reports the discovery of hybrid bipolar electrides in bilayer SnO and PbO, with enhanced semiconducting gaps and unique electride states in both valence and conduction bands.

Findings

Bilayer SnO and PbO are semiconducting electrides with bipolar electride states.

Enhanced bandgap up to 2.5 eV due to covalent-like interactions.

High carrier mobility potential for p-type semiconductor applications.

Abstract

In conventional electrides, excess electrons are localized in crystal voids to serve as anions. Most of these electrides are metallic and the metal cations are primarily from the s-block, d-block, or rare-earth elements. Here, we report a class of p-block metal-based electrides found in bilayer SnO and PbO, which are semiconducting and feature electride states in both the valence band (VB) and conduction band (CB), as referred to 2D "bipolar" electrides. These bilayers are hybrid electrides where excess electrons are localized in the interlayer region and hybridize with the orbitals of Sn atoms in the VB, exhibiting strong covalent-like interactions with neighboring metal atoms. Compared to previously studied hybrid electrides, the higher electronegativity of Sn and Pb enhances these covalent-like interactions, leading to largely enhanced semiconducting bandgap of up to 2.5 eV. Moreover, the CBM primarily arises from the overlap between metal states and interstitial charges, denoting a potential electride and forming a free-electron-like (FEL) state with small effective mass. This state offers high carrier mobilities for both electron and hole in bilayer SnO, suggesting its potential as a promising p-type semiconductor material.