Employing density functional theory–based methods, we investigate monolayer and bilayer structures of hexagonal ${\mathrm{SnS}}_2$, which is a recently synthesized monolayer metal dichalcogenide. Comparison of the $1H$ and $1T$ phases of monolayer ${\mathrm{SnS}}_2$ 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 ${\mathrm{SnS}}_2$ is weaker than that of typical transition-metal dichalcogenides so that alternative stacking orders have similar structural parameters and they are separated with low energy barriers. A possible signature of the stacking order in the ${\mathrm{SnS}}_2$ 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 ${\mathrm{SnS}}_2$. It is found that (i) the electric field increases the coupling between the layers at its preferred 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 ${\mathrm{SnS}}_2$ can become a semimetal, (iii) the most favorable stacking order can be switched by charging, and (iv) a loading pressure exceeding 3 GPa changes the stacking order. The E-field tunable band gap and easily tunable stacking sequence of ${\mathrm{SnS}}_2$ layers make this 2D crystal structure a good candidate for field effect transistor and nanoscale lubricant applications.

• Received 13 January 2016

DOI:https://doi.org/10.1103/PhysRevB.93.125403