# Band Gaps of Hexagonal ScN and YN Multilayer Materials

## TL;DR

This paper studies the electronic properties of hexagonal ScN and YN materials, finding significant variations in band gaps across different layer thicknesses.

## Contribution

The study reveals a wide tunability of band gaps in ScN and YN multilayers using hybrid DFT calculations with spin–orbit coupling.

## Key findings

- ScN-based two-dimensional materials show band gaps ranging from 1.39 to 3.59 eV depending on layer count.
- Few-layer YN materials exhibit low work functions, suggesting potential for electron emission applications.
- Band gap variations are attributed to subsurface ion contributions and conduction band shifts.

## Abstract

The structural parameters and electronic structures of Sc- and Y-based nitride semiconductors that adopted hexagonal BN-like atomic sheets were investigated with calculations based on density functional theory (DFT). A hybrid exchange-correlation functional and spin–orbit coupling were employed for studies on the band structures. A strong variation in the band gap type, as well as the width, was revealed not only between the monolayer and bulk materials but also between the multilayer systems. An exceptionally wide range of band gaps from 1.39 (bulk) up to 3.59 eV (three layers) was obtained for two-dimensional materials based on ScN. This finding is related to two phenomena: significant contributions of subsurface ions into bands that formed a valence band maximum and pronounced shifts in conduction band positions with respect to the Fermi energy between the multilayer systems. The relatively low values of the work function (below 2.36 eV) predicted for the few-layer YN materials might be considered for applications in electron emission. In spite of the fact that the band gaps of two-dimensional materials predicted with hybrid DFT calculations may be overestimated to some extent, the electronic structure of homo- and heterostructures formed by rare earth nitride semiconductors seems to be an interesting subject for further experimental research.