Theoretical Studies On The Epitaxial Growth Of Antimonene And The Electronic Property Modulation Of Antimonene Heterostructures

Antimonene has been widely used in photovoltaic electronics,field effect transistors,battery materials,sensors,thermoelectric devices and biomedical applications due to its excellent physicochemical properties such as high carrier mobility,low thermal conductivity,layerdependent metal-semiconductor transition properties and high environmental stability。This thesis is based on first-principles calculations and investigates two hot topics in antimonene research。One is to investigate the growth of antimonene on metal substrates and elucidate its growth mechanism;The other is to develop new antimonene-based heterostructures and explore their applications.Metals(Ag,Au,Cu,etc.)are common substrates for the epitaxial growth of 2D materials and have also been employed in the experimental preparation of antimonene.Theoretical simulations of the epitaxial growth of antimonene on metal substrates are essential to provide a valuable reference for the experimental preparation of antimonene.In this thesis,the growth mechanism of antimonene on the surface of Ag(111)has been studied and the simulations of the epitaxial growth of antimonene on other metal substrates have also been carried out.Theoretical simulations show that both α-and β-antimonene can be grown epitaxially on Ag(111)substrate,and that the presence of the surface alloy Ag2Sb is conducive to the growth of antimonene.Transition State Theory calculations show that the energy barrier for replacing silver atoms with antimony atoms is much greater than the adsorption energy of antimony on Ag(111)substrates,so that replacement only occurs with sufficient external energy;The high energy barrier allows the surface alloy to remain stable after the replacement has occurred;The formed surface alloy is Ag2Sb,not AgSb2.In the early stages of growth,small antimony clusters of planar polyatomic rings of 3-6 atoms can be seen on the substrate.As the number of antimony atoms deposited increases,the four-or six-atom ring expands to form α-orβ-antimonene.When antimony is grown on the surface alloy Ag2Sb,the deposited antimony atoms fall first on top of the antimony atoms in the alloy layer due to the strong Sb-Sb bonding,stabilizing the antimonene structure and promoting the growth of antimonene.In this work,two competing growth pathways for antimonene on the surface alloy Ag2Sb were found:first,a stable half-layer α-phase structure growing into a full-layer α-antimonene;second,a polyatomic ring structure growing into a β-antimonene.We experimentally verified the growth ofα-antimonene on the surface alloy Ag2Sb and further confirmed the half-layer-by-half-layer growth mode.The growth of antimonene on Au(111)substrate is similar to that on Ag(111)substrate due to the similar lattice constants and the same outermost electron arrangement;on Cu(111)substrate the growth of β-antimonene is preferred;on Al(111)substrate it is difficult to grow antimonene;on Pb(111)it is possible to grow β-antimonene.Antimonene-based heterostructures often exhibit electronic properties beyond those of antimonene and are promising new nanomaterials。Using the concept of epitaxial growth,we can epitaxially grow antimonene on semiconductor substrates to build new antimonene-based heterostructures。In this work,we have chosen Half-Heusler TiPtGe,which is similar to β-phase antimonene,as the substrate,The structural and electronic properties of its heterostructures have been analysed and the following conclusions have been reached:TiPtGe is a stable two-dimensional indirect bandgap semiconductor with a strain-tunable indirect to direct bandgap transition;Due to the presence of hanging bonds on its surface,the electronic structure of TiPtGe changes significantly during the transition from monolayer to multilayer。Therefore,the β-Sb/TiPtGe heterostructures also show strong interlayer interactions,with strong hybridization of electron orbitals at the conduction band minimum.As the number of TiPtGe layers increases,the heterostructure shows a transition from indirect to direct bandgap,and at the same time the heterostructure can significantly improve the light absorption of antimonene in the visible region,demonstrating that the β-Sb/TiPtGe heterostructure is a potential material for optoelectronic devices.In addition,we have predicted the 2D structure of a series of Half-Heusler materials and discovered several stable 2D semiconductor materials similar to TiPtGe,further enriching the list of ternary 2D materials。Experimental and theoretical analytical work on the epitaxial growth of Se on Al(111)surfaces to form surface alloy of AlSe is presented.