First-principles Study Of The Electronic Structure And Magnetism Of Vacancies In The 1T' Phase Of Two-dimensional Janus Materials

The metastable 1T'phase of layered transition metal dichalcogenides(TMDs)has recently attracted considerable interest due to unique electronic properties,possible topological phases,and catalytic activity,especially the monolayer(ML)1T'-MX₂ have been fabricated successfully in experiments.Similar to 2D TMDs,the 1T'phase of ML Janus TMDs is also found and explored theoretically.However,until to now,no one has investigated the vacancy defect on the properties of the 1T'phase of ML Janus MoSSe.It remains unknown how the electronic and magnetic properties in the 1T'phase of Janus MoSSe become in the presence of defects and vacancies.In this paper,by means of first-principles calculations and density function theory,we systematically investigate the impact of the vacancy,antisite,and complex defects on the the stable geometry,formation energy,electronic and magnetic properties of the 1T'phase of ML Janus MoSSe.Firstly,we investigate the geometry,energy,electronic properties of semiconductor2H phase,metallic 1T phase and distorted octahedral coordinated 1T'phase.The research results show that the stability order of these three phases is 2H,1T'and 1T in descending order from the energetic perspective.The new distorted phase 1T'-MoSSe is a semiconductor with indirect band gap,and near the Fermi surface,the Dirac-type linear dispersion is shown at the bottom of the conductive band and the top of the valence band.In addition,we also find that the ML Janus 1T'-MoSSe is non-magnetic.Then,we further investigate the stable geometry,formation energy,and magnetic and electronic properties modulated by the vacancy,antisite,and complex defects in the1T'phase of monolayer Janus MoSSe.For different vacancy defects,the research results show that 1T'-V?Se(A)vacancy and 1T'-V?Mo(B)vacancy are the most favorable intrinsic defects in the Mo-rich and S-rich conditions,respectively.Interestingly,for the vacancy defects of three different atoms Mo,S and Se,the two distinct atom vacancy configurations of each of them can produce the metallic and semiconductive phases in ML Janus 1T'-MoSSe.Therefore,the band gap of the original ML Janus 1T'-MoSSe can be efficiently modified by introducing defects and vacancies.In addition,for the antisite defect system,it is found by calculation that the magnetism can be induced in ML Janus1T'-MoSSe only by the 1T'-Mo-Se(A)and 1T'-Mo-S(A)antisite defects.For the complex defects case,we find that the magnetism can be induced and is widespread for different types of vacancy in the 1T'-MoSSe substrate.Therefore,the electronic and magnetic properties in ML Janus 1T'-MoSSe can be effectively modulated by different defects.These results provide important guidance for the further study of functional devices based on ML 1T'phase of Janus transition metal dichalcogenides,and may have a potential application for spintronics and optoelectronics.