Observation Of Plasmon In Topological Insulator Bi₂Te₃ And Carrier Dispersion In Perovskite Film With S-SNOM

In recent years,the plasmons of two-dimensional nanomaterials,such as graphene and topological insulator have attracted great attention.Because of their unique properties,for example,long lifetime and propagation length,plasmons of the layered two-dimensional materials become more significant in the research values than traditional noble metal like gold and silver.The near-field optical microscope?SNOM?is an important member in the family of high resolution techniques known as Scanning Probe Microscopy?SPM?and can be widely applied to many different research areas.The remarkable material specificity of the near-field optical maps-particularly at infrared frequencies-makes s-SNOM a highly valuable analytical method for non-destructive mapping of chemical,structural,and photo-electric properties on the nanometer scale.In this thesis,we mainly excite and observe the plasmons in topological insulator?TI?bismuth telluride?Bi₂Te₃?single crystal with s-SNOM,and try to tune the plasmons in different two-dimensional materials.Beyond that,we also scan the distribution of free carriers in perovskite using SNOM.The main research content is shown as follows.1.we demonstrate the results of the plasmons in thin Bi₂Te₃ single crystal.We successfully observe the plasmons of topological insulator in real space.What's more,we discover special edge mode fringes surrounding the Bi₂Te₃ flakes.The plasmon we observed associate with the massless surface state electrons.2.we tune the plasmons of graphene and Bi₂Te₃ crystal with gate-voltage successfully.The wavelength of graphene plasmons can be tuned from 140 nm to 280 nm,and we find some special structure on graphene can strongly affect the propagation of plasmon.Besides,the plasmon of Bi₂Te₃ can also be tuned by gate-voltage,and the phenomenon is similar to graphene plasmon,and the tunable plasmon is also mainly excited by the surface state electrons.3.we also scan the distribution of free carriers in perovskite and reveal that the synthesis method and treating processes can significantly affect the size of grain,free carrier concentration and stability in perovskite film.