Investigation On Electronic And Magnetic Properties Of Functionalized One-dimensional Penta-graphene And InSe Nanomaterials

In recent years,graphene and lots of carbon-based and graphene-like two-dimensional materials,such as h-BN monolayer,antimonene,germanium,penta-graphene,typical III-VI group semiconductor indium selenide(InSe),have attracted much attention due to their unique physical properties.Meanwhile,quasi-one-dimensional nanoribbons derived from these two-dimensional materials are expected to be widely used in the new generation of electronic technology.In this thesis,we systematically study the electronic and magnetic properties of one-dimensional penta-graphene nanoribbons and InSe nanoribbons by first-principle calculation based on density functional theory,and focusing on their properties tuned by edge chemical modification and mechanical strain.The purpose is to provide valuable references for the design of nano-electronic devices and spin-electronic devices.The main contents of the study are concluded as follows:Firstly,we introduce the research background of penta-graphene and InSe materials,the research actuality,as well as the main research methods in this paper.Subsequently,we cut the two-dimensional penta-graphene to obtain the five types of penta-graphene nanoribbons with nonmetallic atoms(H,N,P,O,S and F)for edge termination,and calculate their electronic properties and carrier mobility.It is found that these functionalized nanoribbons hold high energy and thermal stability,and are very sensitive to the terminated atoms on the edge.In particular,ZZ-,ZA-,AA-type nanoribbons can be converted from metal or quasi-metal by termination of O and S atoms.SS-type nanoribbons have always been semiconductor properties in the case of termination of all non-metallic atoms,which is closely related to the coupling of termination atoms with the edge C atoms to suppress their edge states.At the same time,depending on the termination atom,these nanoribbons also exhibit rich carrier mobility characteristics ranging from 101 to 104cm2 V-1s-1 at room temperature.S atom termination leads to significant carrier polarization in all nanoribbons.We also study the interesting size effects of some nanoribbons carrier mobility.Recently,the single-layer InSe structure has been successfully manufactured experimentally,and researchers have conducted extensive research on it.On this basis,we studied the geometric stability and various physical properties of InSe nanoribbons,such as electronic and magnetic properties,transport properties and strain effects.Calculations show that all InSe nanoribbons have satisfactory structural stability.At the same time,bare-sided and H-saturated armchair nanoribbons are indirect bandgap semiconductors,but their band saps are significantly increased after saturated by H atoms.Their electron mobility is moderate(from?102 to 103cm2 V-1s-1).In addition,for a wider nanoribbon,the mobility of holes is relatively small,and this carrier polarization phenomenon is more pronounced at H saturation.Of particular importance,we have found that the zigzag InSe nanoribbon is a magnetic metal with a large magnetic moment and a single-sided ferromagnetic ground state.This magnetism is derived from unpaired electrons at In-rich edge.More interestingly,we also find that the externally applied mechanical strain can effectively adjust the spin polarization efficiency(SP)at the Fermi level by two stages,indicating that the strain can be used as a mechanical switch tool to control the spin-polarized transport at lower bias voltages.Further detailed analysis shows that this strain adjustment mechanism can be attributed to the competitive mechanism of ionic bonds and covalent bonds,which are due to the change in bond length induced by strain,leading to the redistribution or disappearance of unpaired electrons in the magnetic atoms.Finally,we calculated the electronic and magnetic properties of the zigzag InSe nanoribbons terminated with nonmetallic atoms(H,B,N,P,F,and Cl).Similarly,the formation energy and Forcite annealing kinetics simulations show that the functionalized InSe nanoribbons have higher energy and thermal stability.The nonmetallic atomic edge termination can regulate the electronic and magnetic properties of the zigzag InSe nanoribbons.The termination of the N atom can enhance the magnetic moment,spin polarization efficiency and magnetic stability of the nanoribbons,while the termination of B and P atoms make the magnetic properties of the nanoribbons disappear.It is also interesting to note that externally applied mechanical strain can enhance the magnetic stability of H-ZN(7)-N and effectively adjust the SP at the Fermi level.The strain modulation mechanism is related to the strain-induced bond-length alterations,which resulting in the redistribution of unpaired electrons.At the same time,the magnetic properties of the zigzag InSe nanoribbons are mainly derived from the p orbitals of N atoms,which is very valuable for the development of non-TM(transition metal)magnetic materials.