The Preparation And Characterization Of Bi₂Se₃topological Insulator Film

Topological insulator is different from some traditional metals and insulators.It is a new quantum functional material.In brief,topological insulator is a new kind of material that is physically insulated and surface conductive.The metal state of the surface is determined by the topological properties of the body electronic state of the material,and is protected by the time reversal symmetry,which is independent of the surface structure of the material.Therefore,the surface metal state is very stable,which can not be affected by the external conditions of impurities and materials in the material.Among them,the bismuth selenide?Bi₂Se₃?is the second generation of three dimensional topological insulators.Bi₂Se₃ has potential applications in the development of thermoelectric,electrochemistry,photoelectric devices and quantum computing because of its controllable chemical stoichiometry,larger energy gap?about 0.3eV?and the state of ultra-low loss on the surface.At the same time,compared with the bulk material of Bi₂Se₃,the low dimensional Bi₂Se₃ nanomaterials have larger specific surface area,more obvious surface electronic state and more prominent topological insulation.Therefore,the controllable preparation of Bi₂Se₃nanomaterials should be achieved for the study of some new physical phenomena and the realization in the related fields of the materials.And it's very important for this field.In this paper,the most representative Bi₂Se₃ in the second generation 3D topological insulator is selected as the research object.Bi₂Se₃ thin film was prepared by chemical vapor deposition?CVD?using high-purity Bi₂Se₃ powder and Se powder.Mainly explore the content:?1?To explore the effect of the addition of Se powder into the Bi₂Se₃ evaporator source powder on the growth of Bi₂Se₃ nanostructured thin films.The results show that the addition of Se powder can improve the crystalline quality and increase the coverage of films,which is beneficial to the lateral growth of Bi₂Se₃ films.?2?To explore the effect of the ratio of Se and Bi on the growth of Bi₂Se₃nanostructured films.The results show that when the ratio of Se to Bi is 5:1,the growth of films is better and the film has a good crystallinity.At the same time,the proportion of Se and Bi atoms is closer to 5:1.?3?To explore the influence of substrate distance to evaporation source on the growth of Bi₂Se₃ nanostructured thin films.The results show that the crystallinity of the film is the best,the size of the grain is larger and the deposition of the film is more uniform when the substrate is placed in the position of about 10cm from evaporator source along the air flow direction.?4?Bi₂Se₃ films were grown at different Ar gas flow rates,and the effect of Ar gas flow on the growth of Bi₂Se₃ nanostructured thin films was investigated.With the increase of gas flow,the crystalline quality of the film increases gradually and the size of the nanoscale increases gradually.When the gas flow rate increases to 45sccm,the Raman spectrum appears a new peak at the position of the Bi₂Se₃ characteristic peak in the position of 250cm^-1.We speculate that the Bi₂Se₃ nanostructure is increased by the lattice pressure stress at 45sccm.The structural phase transition is strong.Finally,we find the best Ar gas flow rate is 40sccm?4.98cm/s?.?5?Bi₂Se₃ films were grown at different growth temperatures to explore the effect of growth temperature on the growth of Bi₂Se₃ nanostructured films.?6?Bi₂Se₃ films were grown at different growth time to explore the effect of growth time on the growth of Bi₂Se₃ nanostructured films.The results show that the Bi₂Se₃ films prepared at the growth time of 15min have good crystallinity,high surface coverage and close to the ideal ratio.