Influences of vacancy and doping on electronic and magnetic properties of monolayer SnS

What is it about?

In the last decade, graphene-like two-dimensional (2D) materials have drawn significant attention especially in the materials science community due to their auspicious electronic and optoelectronic properties that are promising for applications such as field-effect transistors (FET) and optoelectronic detectors. Among the various reported 2D materials, monolayer tin sulfide (SnS), a phosphorene analogue, is recently at the helm of enormous interest because of its remarkable properties. For instance, it has an interference effect, 6 a high absorption coefficient of light, a high free carrier concentration, and low toxicity. Earth-abundant SnS is also a potential candidate for photovoltaic devices. Furthermore, nanosheets of SnS exhibit higher electron mobility than MoS2. Also, monolayer SnS exhibits multiferroic properties with ferroelectricity and ferroelasticity at room temperature and possesses enormous anisotropic piezoelectric effects, making it suitable for applications in nano-sized piezoelectric and sensing devices. Hasan et al. successfully synthesized thin films of SnS by using the thermal evaporation process. The nano flakes of SnS have also been synthesized successfully by the physical vapor deposition (PVD) method. It has been reported that SnS nano-flakes have higher sensitivity to temperature than other 2D materials such as graphene, MoS2 , and black phosphorus. These reported studies also illustrate that monolayer SnS is a promising material for thermoelectric devices.

Featured Image

Why is it important?

In this study, we investigate the effects of vacancies (both Sn- and S-site vacancies) and doping of TM (TM 1⁄4 Mn, Fe, and Co) elements at the Sn-site in the semiconducting monolayer SnS using density functional calculations. We find that vacancy formation at the Sn-site can be easier than that at the S-site in experiments with energetic particle irradiation. However, the growth environment may play a vital role in the formation of vacancies. We find that the vacancy at the S-site (Sn-site) for the Sn (S) rich environment is more likely to be found than the vacancy at the Sn-site (S-site). Additionally, we study the vacancy migration to see how easily the vacancy can move from the initial position where it is created to some other places. Interestingly, we find that the S vacancy remains robust due to a high vacancy migration barrier, reducing the possibility of vacancy cluster formation. A semiconductor-to-metal transition occurs with the creation of the vacancy at the Sn-site. Our results show that the TM atom doping can induce magnetism in the non-magnetic monolayer SnS with high magnetic moments, which could be promising to realize two-dimensional diluted magnetic semiconductors. Thus, the doped SnS monolayer could serve potential applications in the field of nanoscale spintronic devices.

Perspectives