Research Of The Growth Of Two-dimensional Antimony Film On Al(111) Substrate

In 2004,the discovery of graphene triggered intensive researches on graphene-like two-dimensional（2D）layered materials,also named as X-enes.In recent years,single-element graphene-like 2D materials have gradually developed from the fourth main group elements（carbon,silicon,germanium,tin）to the fifth main group elements（phosphorus,arsenic,antimony,bismuth）.Although the mono-elemental X-enes,composed of the fifth main group elements,is similar to graphene in atomic structure and electronic properties,it also has some unique characteristics,such as a relative larger band gap and strong spin-orbit coupling（SOC）.Antimonene is an intriguing single-element graphene-like 2D material,because of its 2.28 e V band gap,strain-tunable band gap,topological non-neutral electronic states and quantum spin hall effect,and so on.The antimony thin films have been mainly synthesized by molecular beam epitaxy method（MBE）.Because MBE method is used in ultra-high vacuum(≤10^-8mbar)environment,the quality of antimony thin films obtained can be very high,and the growth rate and layers can be controlled.At present,the epitaxy growth of antimony thin films on Au（111）,Ag（111）and Cu（111）substrates have been achieved by MBE method.However,there are few studies on the epitaxy growth of antimony thin films on Al（111）metal substrate.Al（111）substrate is a common metal substrate,which has perfect thermal and electronic properties,and on which 2D germanene films and stannene films have been successfully grown.Above on,Al（111）metal substrate may be a perfect substrate for epitaxial growth of antimony thin film.In this thesis,two types of antimony film were successfully grown on Al（111）substrate by MBE method.The evolutionary process of the two antimony films on Al（111）substrate were investigated by reflection high-energy electron diffraction（RHEED）and X-ray photoelectron spectroscopy（XPS）experiments.We also investigate the atomic structures by in-situ scanning tunneling microscope（STM）experiment.Furthermore,we also carried out the first-principles calculation to investigate the structure of the two types of antimony films.The main conclusions in the thesis are as following:（1）Sb nanoclusters were deposited on Al（111）substrate at room temperature and further investigated by in-situ XPS,RHEED and STM measurements.When the deposition time is short（t≤2 min）,Sb nanoclusters were inclined to absorb on the surface of Al（111）substrate in an order-less lattice.With the increase of deposition time（2 min≤t≤8 min）,the ordered smaller islands with“Triangular lattice”appear near the step edge of Al（111）substrate,and gradually evolved into larger islands,and even form a continuous full-covered film finally.Further increasing the deposition time（8 min≤t≤16 min）,structure phase transition will be appeared,transforming from“Triangular lattice”to the“Kagome-like lattice”;Finally,continue to increase the deposition time（t≥16 min）,the film with Kagome-like lattice will be covered by disordered antimony nanoclusters.（2）The Sb atoms were deposited on Al（111）substrate for 16 min and then annealed 30 min at a series of temperatures,ranging from 60℃to 330℃.Annealed at below 240℃,the disordered antimony nanoclusters have no significant changes in content and existence form.Annealed at above 240℃,the disordered antimony nanoclusters desorbed from the surface,and the Kagome-like lattice exposed at the surface.annealed at the temperature ranging from 240℃and 280℃,the Kagome-like lattice evolved into Triangular lattice.Annealed at above 280℃,the Triangular lattice was destroyed and the remaining order-less antimony atoms attached to the surface of Al（111）surface.（3）The detailed atomic structures of the two types of structures were obtained by STM measurements.And we also constructed the corresponding atomic model for the two structures by VASP software.The first principles calculation method proves that these two structures are stable,and the STM simulation results are in good agreement with our experiments.In addition,we guessed that the strong interaction between substrate atoms and Sb atoms and the strong anisotropy characteristics were the reason for the formation of the Kagome-like lattice through ELF（Electron Local Function simulation）mapping.