Synthesis And Characterization Of Topological Insulator Material

Topological insulators are a specific class of insulator with an insulating bulk state,but the surface is metal state with time-reversal invariant caused by strong spin-orbitinteraction. Electrons go their own way without disturbing each other in topologicalinsulators, which avoids electronic energy consumption caused by the disorder collisionof electrons. It has important significance to solve the semiconductor industry and eventhe whole information technology development. Bi2Se3, the second generation of three-dimensional topological insulator, has become the focus of attention and research inrecent years. Because it is a pure chemical phase; its surface states has only one Diracpoint, which is closest to the ideal state of strong topological insulators; the bandgap is0.3eV (equivalent to3600K), which is currently the largest bandgap in topologicalinsulators.In this article, the development, classification and application of topologicalinsulator were summarized. And we select the most representative of the topologicalinsulator Bi2Se3as the research object. Topological surface properties of Bi2Se3crystalcan easily be covered with the bulk state, so it is difficult to observe the phenomenon oftopological insulator. For the large surface-to-volume ratios of nanomaterials, Bi2Se3nanostructures is beneficial to study its unique surface state. It is very important for thepractical application of the device. The economic efficiency of chemical vapor deposition(CVD) method was used to prepare Bi2Se3nanostructures in this paper, and the researchcontents are as follows:(1) By the addition of Se powder in the Bi2Se3powder evaporation source toexplore the effect of Se on synthesis of Bi2Se3nanostructures. The addition of Se powderin source improves the crystalline quality of Bi2Se3, promotes the lateral growth of Bi2Se3nanostructures, and ensures that the Se and Bi atomic ratio is more close to the standard value of1.5. At the same time, the blue shift of Bi2Se3Raman vibration peaks A11gandE2goccurred.(2) Synthesis Bi2Se3at different growth temperatures and exploration the impact oftemperature on Bi2Se3nanostructures. With the rising of temperature, the crystallinequality of prepared Bi2Se3is getting better; the surface size also increases; the growthmechanism becomes VS from VLS; but the atomic ratio of Se and Bi declines. Theappearance of bismuth oxide in the products at650°C results in the red shift of Ramanvibration peaks A11g. Finally, the optimum temperature of500°C was found.(3) At the same temperature (500°C), synthesis Bi2Se3in different growth time andinvestigation the effect of growth time on Bi2Se3nanostructures. With the growth timeincreasing, the crystalline quality of the obtained Bi2Se3nanostructures graduallyimproved, and tended to stabilize after about10minutes; the surface size of Bi2Se3nanoplates has increased; Raman peak intensity first increased and then decreased; theatomic ratio of Se:Bi decreased. Eventually, find optimal growth period of10-20min.（4）Transfer the graphene, which is synthesized on copper foil by chemical vapordeposition method, to SiO2substrate by wet transferring method. Using graphene as abuffer layer to synthesize Bi2Se3, and study the effect on the preparation of Bi2Se3nanosheets. The addition of grapheme is beneficial to improve the crystalline quality ofBi2Se3nanoplate, and increases the thickness of nanoplate too. Moreover, due to theparticipation of graphene, the in-plane vibration peak E2ghappened red shiftphenomenon.