Bilayer SnS$_{2}$: Easy-tunable Stacking Sequence by Charging and Loading Pressure

TL;DR

This study uses density functional theory to explore how external electric fields, charging, and pressure can tune the stacking sequence and electronic properties of bilayer SnS₂, revealing its potential for electronic and lubricating applications.

Contribution

It demonstrates that external stimuli can easily switch stacking orders and tune the bandgap of bilayer SnS₂, a novel feature for 2D materials.

Findings

Electric field increases interlayer coupling and barrier height.

Bandgap can be tuned by electric field, enabling semi-metallic states.

Charging and pressure can switch stacking configurations.

Abstract

Employing density functional theory-based methods, we investigate monolayer and bilayer structures of hexagonal SnS$_{2}$, which is recently synthesized monolayer metal dichalcogenide. Comparison of 1H and 1T phases of monolayer SnS$_{2}$ confirms the ground state to be the 1T phase. In its bilayer structure we examine different stacking configurations of the two layers. It is found that the interlayer coupling in bilayer SnS$_{2}$ is weaker than that of typical transition-metal dichalcogenides (TMDs) so that alternative stacking orders have similar structural parameters and they are separated with low energy barriers. Possible signature of the stacking order in SnS$_{2}$ bilayer has been sought in the calculated absorbance and reflectivity spectra. We also study the effects of the external electric field, charging, and loading pressure on the characteristic properties of bilayer SnS$_{2}$. It is found that (i) the electric field increases the coupling between the layers at its prefered stacking order, so the barrier height increases, (ii) the bang gap value can be tuned by the external E-field and under sufficient E-field, the bilayer SnS$_{2}$ can become semi-metal, (iii) the most favorable stacking order can be switched by charging and (iv) a loading pressure exceeding 3 GPa changes the stacking order. E-field tunable bandgap and easy-tunable stacking sequence of SnS$_{2}$ layers make this 2D crystal structure a good candidate for field effect transistor and nanoscale lubricant applications.