Scanning Tunneling Microscopy Study On The Epitaxial Growth Of Tin

With the development of research on two-dimensional materials,elemental two-dimensional materials with honeycomb lattices have attracted much attention.Among them,stanene,a monolayer crystal of Sn,can produce large gap quantum spin Hall states due to its strong spin-orbit coupling.It is an ideal material for studying the dissipationless electric conduction and topological superconductivity.Due to its novel physical properties and potential applications,stanene has become an important research topic in the field of condensed matter physics.In this thesis,we focus on the experimental preparation of two-dimensional tin strucutres.The epitaxial growth of Si on Si(111)and MoS2 substrates is carried out by molecular beam epitaxy under ultra-high vacuum conditions.By using scanning tunneling microscopy,the growth behavior and structure evolution of Sn on different substrates are investigated at the atomic scale.The results are as follows:Firstly,the initial growth behaviors of Sn on Si(111)reconstructed surfaces ha've been analyzed and compared.The experimental results show that on the 7×7 surface,Sn preferentially adsorbs in the 7×7 half unit cells to form clusters due to the influence of the substrate structure.By controlling the annealing temperature and Sn coverage,ordered Sn cluster arrays can be obtained.On the 2(?)× 2(?)-Sn surface,Sn tends to adsorb on the domain boundary or defects to form nanoparticles due to the low binding energy with the substrate.In the(?)×(?)reconstruction regions,Sn exhibits a two-dimensional growth mode and arranges into planar epitaxial structures.According to the growth characteristics of Sn,we constructed a Si(111)-(?)×(?)-Sn reconstructed surface as the substrate,and obtained a two-dimensional Sn thin film with monoatomic layer thickness.On the other hand,the epitaxial growth and structure evolution of Sn on MoS2 substrate have been studied.It is observed that Sn follows the SK growth as depositing on MoS2 at room temperature.The Sn particles degrade into the Sn layer underneath after the appropriate annealing treatment,forming a Sn adlayer with local stacking structure.With the increase of annealing temperature,Sn agglomerates to form large-sized metal particles,and produces the etched depression areas with a triangular or hexagonal shape and long etching trails on the substrate.The results provide scientific data for the fabrication of two-dimensional Sn-based films and related low-dimensional structures.