Layer-dependent Raman spectroscopy and electronic applications of wide-bandgap 2D semiconductor \b{eta}-ZrNCl

TL;DR

This study isolates monolayer ta-ZrNCl, investigates its layer-dependent Raman properties, and demonstrates its potential for electronic devices due to its wide bandgap and high on/off ratio.

Contribution

First isolation of monolayer ta-ZrNCl and systematic analysis of its layer-dependent Raman spectra for electronic applications.

Findings

Monolayer ta-ZrNCl has a bandgap of ~3.0 eV.

The A1g Raman peak shifts with layer number and is absent in monolayer.

Few-layer ZrNCl FETs exhibit a high on/off ratio of 10^8.

Abstract

In recent years, two-dimensional (2D) layered semiconductors have received much attention for their potential in next-generation electronics and optoelectronics. Wide-bandgap 2D semiconductors are especially important in blue and ultraviolet wavelength region, while there are very few 2D materials in this region. Here, monolayer \b{eta}-type zirconium nitride chloride (\b{eta}-ZrNCl) is isolated for the first time, which is an air-stable layered material with a bandgap of ~3.0 eV in bulk. Systematical investigation of layer-dependent Raman scattering of ZrNCl from monolayer, bilayer, to bulk reveals a blue shift of its out-of-plane A1g peak at ~189 cm-1. Importantly, this A1g peak is absent in monolayer, suggesting that it is a fingerprint to quickly identify monolayer and for the thickness determination of 2D ZrNCl. The back-gate field-effect transistor based on few-layer ZrNCl shows a high on/off ratio of 108. These results suggest the potential of 2D \b{eta}-ZrNCl for electronic applications.