Theoretical Studies On The Electronic Structure And Properties Of MX(M=Ga,In,X=S,Se,Te)Nanoribbons

Since the special properties of ?A-?A compounds MX(M = Ga,In;X = S,Se,Te),such as high carrier mobility,dark-shaped valence band edges,rare p-type electron behavior,etc.,they have been widely studied in recent years.Recently,successful experimental synthesis has sparked a wave of research on MX materials.The wide band gap of 1.40-2.50 eV make them more advantageous than molybdenum disulfide,especially in semiconductor and optical device applications.The structure of each material determines its properties.One-dimensional structures such as field-effect transistors,nanoribbons,and nanotubes obtained from twodimensional nanosheets exhibit different optical,mechanical,and electrical properties.For example,single-layer graphene nanosheets exhibit the characteristics of non-magnetic semimetals,while armchair nanoribbons behave as non-magnetic semiconductors,while zigzag naanoribbons are magnetic metals.The size and edge characteristics of the nanoribbons determine the band gap of the armchair nanoribbons and the magnetic properties of the zigzag nanoribbons,respectively.The effects of these size and edge characteristics can also be found in phosphene,metal oxides and transition metal chalcogenides,etc.A large number of two-dimensional materials and one-dimensional materials will inevitably encounter different functional groups(such as hydrogen,oxygen and fluorine functional groups),different atom replacement or doping effects and vacancy effects in the experimental preparation process and practical application These effects all affect the structure and electronic properties of the material.For example: intrinsic zigzag graphene nanoribbons have antiferromagnetic metallic properties,while single-edge fluorination can degrade spin and show semiconductor properties;while double-edge fluorinated small-sized zigzag nanoribbons are non-magnetic semiconductor properties,The large-sized zigzag nanoribbon is a semiconductor characteristic of double-edge polarization.In this paper,based on the density functional theory,using the first-principles,we have calculated two-dimensional MX nanosheets and one-dimensional MX nanoribbon models with different widths and edges in theVASP software package,and further explored its electronic properties and magnetic properties,the main contents are as follows:1)The one-dimensional nanoribbon model is cut from the nanosheet monolayer.We studied the electronic structure for the MX nanosheet and the electronic structure and magnetism for the MX nanoribbon.Calculations show that: MX nanosheets have non-magnetic p-type semiconductor behavior;for both types of MX nanoribbons,all armchair nanoribbons behave similarly to non-magnetic semiconductors,and their band gaps are regulated by the size and the atomic number of X,with exhibiting parity-width oscillation behavior.The corresponding band gap converges to a band gap lower than that of the single-layer nanosheet due to the introduction of a new flat band by edge recombination.The small-sized zigzag nanoribbons break the sixmembered ring structure,and the edge metal atoms move to the center,showing a non-magnetic semiconductor behavior,but the large-sized zigzag nanoribbons are all metals.Among them,MTe is non-magnetic,which is different from graphene and phosphene nanoribbons.In contrast,the MX(M = Ga,In;X = S,Se)zigzag nanoribbons show ferromagnetism due to the unpaired electrons on the metal edge side,and the magnetic moment of each pair of molecules is controlled by the size of the nanoribbons.2)Considering that our calculations are all obtained through theoretical simulation,and in experimental synthesis and application,it will inevitably be oxidized.We studied the MX(M = Ga,In;X = S,Se)nanoribbons modified with O functional groups on the metal edge.Studies have shown that the introduction of O-functional groups to passivate armchair nanoribbons is still a non-magnetic direct bandgap semiconductor behavior,and the zigzag nanoribbons exhibit semiconductor characteristics by opening the bandgap while retaining the ferromagnetic properties.None of the band gaps of MX nanoribbons have a size effect,and the magnetic moment is slightly lower than that of intrinsic nanoribbons.The different results that may be brought by the experimental environment during the synthesis of MX nanoribbons,we studied the effects of these results on the electronic structure and magnetic properties of MX nanoribbons,the size effect of the electronic properties of intrinsic nanoribbons,and single-edge O functional groups The modified uniform electronic properties may make MX materials a key advantage in future semiconductor device applications.