MBE Growth And STM Study Of Group Va Sb And Bi Thin Films

Due to its good features such as tunable direct bandgap,high carrier mobility,high on-off ratio,and substantial anisotropy,black phosphorus(BP)in Group VA is a possible candidate material for optoelectronic devices.However,few-layer black phosphorus(BP)is unstable in the atmosphere,which severely restricts its application.Arsenic(As),antimony(Sb),and bismuth(Bi)have all drawn a lot of attention as materials in the same group as P.Toxic arsenic has gotten little attention,but non-toxic Bi and Sb with outstanding characteristics have gotten more..Antimonene is a two-dimensional material with excellent air stability,a potential quantum spin Hall effect,and a strain-induced band transition..Low-dimensional Bi has also many excellent properties such as high thermoelectric efficiency,potential superconductivity,semimetal-to-semiconductor transition,and topological properties In this paper,we use molecular beam epitaxy(MBE)to study the epitaxial development of Group VA Sb and Bi,as well as scanning tunneling microscopy(STM)and scanning tunneling spectroscopy to characterize their lattice structures and electronic structure(STS).The essential points of this paper will be summarized simply below.1.Using scanning tunneling microscopy,we studied the structural development of Sb on the Ag(110)surface as coverage increased..At low coverage(θ ≤ 0.5 ML),Sb atoms enter the topmost layer of Ag(110),forming the Ag Sb alloy confined to the surface,and the replacement Ag atoms disperse in the Ag(110)region,combining with other deposited Sb atoms to form order c(2× 2)reconstruct alloy islands.The surface alloy formation is explained using a simple model schematic..As the coverage is slightly more than 0.5 ML,short strip-like structures begin to appear at the edge of alloy islands.The surface is totally covered by nano-strips along the 1 10 direction when the coverage reaches a specified level.The nano-strips no longer morph into different structures as the coverage increases.2.We have successfully grown high-quality,single-oriented Bi(110)thin films of 1 BL and 2 BL with black phosphorus-like structures on Sn Se substrates using molecular beam epitaxy.Scanning tunneling microscopy/spectroscopy(STM/S)is used to investigate the lattice structure and electronic structure of Bi(110).Both 1 BL and 2 BL Bi(110)exhibit large-period orthorhombic Moiré superlattices,and the periodic Moiré superlattice modulates the electronic states of the surface.We also see hump-like superstructural reconfigurations around the edges of 1 BL Bi(110)islands,which could lead to non-trivial topological edge states.