The Electronic Structures Of The Interface Of Monolayer SnSe And Transtion Metals Doped SnSe Film

Tin selenide(SnSe)as a chemical stability and earth-abundant semiconductor,has the multiexciton generation effect.Its direct band gap and indirect band gap fall within the optical band gap.SnSe has been explored as the potential optical material for memory switching,solar cells,sensors and photo detector,et al.Due to the potential optical property,human ignore its potential property in metal-semiconductor contact and diluted magnetic semiconductor.Therefore,in this paper,we study the characteristics of SnSe/M contact and doped SnSe using the first-principles calculation method.The main results are given as follows.Firstly,theinterfacialproperties are investigated in the SnSe/M(M=Ag,Au,Ta)contacts by means of first-principles calculations.The computed results show thatcompared with the corresponding free-standing monolayer SnSe,the geometries of adsorbed SnSewas affected slightly.Due to the interaction between monolayer SnSe and M substrate,the semiconductor SnSe undergoes a semiconductor-to-metal transition.The interfacial average electric potential difference ?V indicates that SnSe/Ta contact is the best candidate for the Schottky contact in the three SnSe/M contacts.There are two types of current-in-plane(CIP)structure will be form,when a freestanding monolayer SnSe adsorbs on the SnSe/M contact.The n-type CIP structure will be formed in SnSe/Ag contact and p-type CIP structure will be formed in SnSe/Au and SnSe/Ta contact.Secondly,the character of bilayer SnSe with transition-metal(TM)atoms doped in the interlayer are investigated by using a first-principles method.The computed results show that Ni dopant cannot induce the magnetism in the doped SnSe sheet,while the ground state of V,Cr,Mn,Fe and Co doped systems are magnetic and the magnetic moment mainly originates from TM-3d orbital.Two types of factors,which reduce the magnetic moment of TM atoms doped in bilayer SnSe,are identified as spin-up channel of the 3d orbital loses electrons to SnSe sheet and spin-down channel of the 3d orbital gains electrons from 4s orbital.The spin polarization is found to be 100% at Fermi level for the Mn and Co atoms doped system,while the Ni-doped system is still a semiconductor with a gap of 0.26 e V.These results show that the Mn and Co doped systems are the best candidate for spintronic devices.Thirdly,TM(TM=V,Cr,Mn,Fe,Co,Ni)atoms doped monolayer SnSe are studied by first-principles calculations.The magnetic ground state is found in all the doped system and the magnetic moment is mainly originate from the TM impurity.Tow different interactions(ferromagnetic interaction and antiferromagnetic interaction)are induced between TM atom and Se atoms.The TM-3d orbital can effectively modulate the SnSe band gap and the spin polarization is 100%(97%)at fermi level for Cr-doped(Fe-doped)system,while the Mn-doped system is still a semiconductor with a gap of 0.33 e V.Furthermore,the interaction in two TM-SnSe system is mainly driven by the occurrence of coupling chains between a first TM-3d to a second TM-3d via a bridging Se-4p and Sn-5s,5p orbitals.The stability of the ferromagnetic ground state can be attributed to the polarized electrons and holes,which located near the Fermi level.The V doped system is promising candidate to explore two-dimensional diluted magnetic semiconductors.