First-Principles Investigation Of Doping And Defect Effect On Monolayer SnS₂

With the discovery of graphene,two-dimensional materials have approached to the scene view of human gradually.Monolayer SnS₂ has received particular attention due to its high chemical stabilization,nontoxicity,low cost and abundance.Unfortunately,monolayer SnS₂ can only absorb most of the ultraviolet light and a small amount of visible light.Besides,although the monolayer SnS₂ is susceptible to the photo-oxidation of water,it is not active for the photo-reduction of water.Additionally,the systematical reports on magnetic properties of monolayer SnS₂ are scarce.Therefore,the development and applications of monolayer Sn S₂ have been limited.More recently,many studies have proved that impurities and defects have a significant influence on the electronic,optical and magnetic properties of monolayer SnS₂.Hence,in the present work,monolayer Sn S₂ was adopted,and the effects of Fe/Zn-doping and instrinsic defects on the electronic,optical and magnetic properties of monolayer SnS₂ have been systematically investigated using the first principles calculations on the basis of density functional theory.For Fe-SnS₂,Fe doping results in not only a decrease of its band gap,but also the realization of room temperature ferromagnetism.In addition,Fe doping can enhance the absorption of solar spectrum in the low energy region.The red shift in the absorption edges is mainly the result of the decrease in the band gaps of Fe-SnS₂.And the additional absorption in the infrared region comes from the intraband transition of Fe-3d states in the impurity band.Moreover,when the doping concentration is 8.33%,the Fe-SnS₂ can achieve the maximum utilization efficiency of the solar spectrum in the whole energy range.While,it should be noted that Fe doping will decrease the photocatalytic activity of monolayer SnS₂.For Zn-SnS₂,Zn doping results in not only a decrease of its band gap,but also the realization of room temperature ferromagnetism.Additionally,Zn doping can also enhance the absorption of solar spectrum in the low energy region.The red shift in the absorption edges is mainly the result of the decrease in the band gaps of Zn-SnS₂.And the additional absorption in the infrared region comes from the intraband transition of S-3p states in the impurity band.While,Zn doping shows a continuous increase for utilization efficiency of the solar spectrum in the whole energy range with the doping concentration.Moreover,Zn doping can also improve the photocatalytic activity of monolayer SnS₂.For monolayer SnS₂ with intrinsic defects,Sn vacancy,Sn-on-S anti-site and S adsorption on the top of S atom from the upper triple layer defects can induce magnetism.Moreover,the room temperature ferromagnetism is possible to be realized in monolayer SnS₂ with S adsorption on the top of S atom from the upper triple layer defects.To sum up,it can be concluded that Fe-doped monolayer SnS₂ can obtain strong absorption and room temperature ferromagnetism which is suitable for solar cell and diluted magnetic semiconductor.Zn-doped monolayer SnS₂ can achieve a good comprehensive performance for solar cell,photocatalysis material and diluted magnetic semiconductor.And room temperature ferromagnetism can also be realized in monolayer SnS₂ with S adsorption on the top of S atom from the upper triple layer defects,which gives a new path to explore monolayer SnS₂-based spintronic devices.