# Discovery of a new zinc oxide semiconductor: 21R polytype

## TL;DR

Researchers discovered a new zinc oxide semiconductor with a 21R crystal structure, showing promising electronic properties for advanced technological applications.

## Contribution

The first prediction of a new 21R polytype in ZnO with direct band gap properties is reported.

## Key findings

- The 21R polytype of ZnO is a direct band gap semiconductor with a band gap of 2.79 eV using HSE06 and 3.42 eV using PBE0.
- Theoretical calculations align with experimental results for known ZnO polytypes.
- The new polytype could enable tailored ZnO for 0D, 1D, 2D, and 3D material applications.

## Abstract

Zinc oxide (ZnO) is a notable semiconductor with a range of interesting electronic and optical properties. Polytypic behavior of crystal structures can strongly affect the properties of materials, especially in ZnO. We report the first prediction of a new 21R polytype in zinc oxide with advanced properties. Ab initio calculations were carried out using two-hybrid functionals: HSE06 and PBE0. Structural properties of different ZnO polytypes were investigated, and theoretical data concurred with experimental results. This can be further exploited for various applications based on their unique properties. Electronic properties were studied using band structures and density of states (DOS). Present DFT calculations agree very well with previous calculations and measurements of known ZnO polytypes, and the new 21R polytype is found as a direct band gap semiconductor. The size of the band gap in the case of the hybrid HSE06 functional is calculated to be 2.79 eV and with PBE0 is 3.42 eV. Understanding the structure–property relationship helps in tailoring ZnO for specific applications and optimizing its performance in various technological contexts, especially as an advanced semiconductor material, with possible applications such as 0D, 1D, 2D, and 3D materials.