Electronic And Transport Properties Of Hybrid System Based On Metal Cluster With Graphene Or MoS₂

The discovery of atomic single-layered graphite(graphene)and its novel properties have attracted broad attention in investigating two dimensional(2D)materials since 2004.There are many kinds of 2D materials have been found,such as single layered hexagonal boron nitride,transition metal dichalcogenides,black phosphorus,silicene,et al.However,due to the localization of outside d orbitals,the formation of free-standing transition metal(TM)monolayer with inherent excellent magnetic and/or catalysis properties remains challenging.In this thesis,we focoused on the electronic and transport properties of composite material of metal clusters and 2D graphene-like materials.By using first-principles calculation,we investigated the growth mechanics of TM clusters on 2D materials and designed new 2D TMMoS2 composite materials with novel electronic,magnetic and photovoltaic properties.The main results are summarized as below:1)Structure and spin-polarized transport of Co atomic chains on graphene with topological line defects.The nucleation growth of Co atoms absorbed on graphene with extended linear defect has been investigated.Based on the analysis of optimized structures,binding energies and diffusion barriers,we predict a patterned growth of linear arranged Co clusters along the linear defect.With the increase of cluster size,Co chain forms gradually and results in the construction of a quasi-one-dimensional(1D)structure(Co/LD@Gr).Moreover,the transport properties of the Co/LD@Gr are investigated by using the non-equilibrium Green's function method combined with density functional theory.We find that the spin current paralleling to the LD is polarized.The spin-resolved transmission pathways and eigen-channels indicate that there is high spin injection from Co chain into graphene.As predetermined location and direction for the LD in graphene have been realized experimentally,this quasi-1D Co/LD@Gr structure would be a compelling and feasible candidate for future spintronic related applications.2)Structural,electronic and magnetic properties of atomically thin layer of RuMoS2 and FeMoS2.We established that Ru and Fe atoms can be epitaxially aligned on MoS2 monolayer,thus forms atomic-thin 2D RuMoS2 and FeMoS2 with kinetic stability.Both Ru and Fe layer are room temperature ferromagnetic ordering with Curie temperature more than 300K.In particular,RuMoS2 possesses an out-of-plane easy axis with the magnetic anisotropy energy(MAE)of?3.4meV/atom.While,FeMoS2 is a novel ferromagnetic half-metallicity with a 100%spin polarized transport.We propose that this atomic-thin layer of RuMoS2 and/or FeMoS2 can be used as an alternative candidate for free-standing magnetic TM layers and provides new possibilities to design 2D spintronic devices.3)Growth morphology of group ? transition-metals on MoS2 and an atomic-thin lateral p-n junction of NiMoS2-MoS2.We systematically analyzed atomic structures of supported(TMvm)n clusters on MoS2 for n=6-9,and found that the growth morphology is dominated by the ratio of adsorption energy of metals on MoS2 to coherent energy of their bulk phase.Due to the large adsorption energy,Ni atoms on MoS2 exhibit the layered growth morphology for n=6-9,meanwhile the phonon spectrum and molecular dynamics simulations further indicate the kinetic and thermodynamic stability of an atomic-thin layer of 2D NiMoS2 in room temperature.In particular,NiMoS2 is a semiconductor and possesses "Type ?" band edge alignment with MoS2.After finding the Ti contactor with appropriate work function,we predict an atomic-thin lateral p-n junction of NiMoS2-MoS2,which can be manufactured by epitaxially growing Ni atoms on specific area of MoS2.This 2D lateral p-n junction is promising in efficient electron-hole separation and show great potential in photovoltaics,such as high-performance photo detectors.