The Preparation,Cu-doped And Its Properties Of Topological Insulator Bi₂Se₃ Nanomaterials

Topological insulator is a new state of quantum matter with an insulating bulk state and metallic surface state which protected by time-reversal invariant caused by strong spin-orbit interaction.The direction of electron spin is opposite in surface state,electrons go their own way without disturbing and impact each other in topological surface state,which avoids electronic energy consumption.It has important significance to solve the heat dissipation of micro-electronic devices and the development of information technology in the future.Bi₂Se₃,which is an ideal phase to study topological insulators.When the topological insulator Bi₂Se₃is doped with transition metal Cu,it is found to exhibit superconductivity at low temperatures,which provides a possibility for the discovery of topological superconductor.The topological surface properties can be easily covered by the bulk state.While according to nanomaterials,the surface state can be enhanced due to the large surface-to-volume ratio.So it is essential to achieve the controllable preparation of Bi₂Se₃nanosructures.In this paper,we used vapor deposition?VD?method to synthesize Bi₂Se₃nanomatirials and Cu-doped nanowires.The related research as shown below:The Bi₂Se₃ nanowires were prepared by VD method based on the VLS?vapor-liquid-solid?mechanism.The impacts of the heating temperature and substrate temperature on the nanowires morphology and Se vacancy were investigated.We found that the length and density of nanowires increased with the rise of temperature,and achieved high crystallinity nanowires of hundreds of micrometers in length at 650?.At 650?heating teperature,it was found that the atomic ratio of Se and Bi increased with the decline of the substrate temperature,and reached the standard atomic ratio of Bi₂Se₃ at 500?.UV-visible?UV?spectrum showed that the Bi₂Se₃ nanowires have an absorbed peak at 226 nm and the bandgap?0.5 eV?of Bi₂Se₃ nanowires was caulated.The luminescence peak of Bi₂Se₃nanowires at 747.2 nm was detected in Photoluminescence spectrum?PL?,which may be ascribed to the decay of excitons.The Bi₂Se₃ nanoplates were prepared at 550?,600?,650?and 700?by VD method based on the VS?vapor-solid?mechanism.The influences of the heating temperature and substrate temperature on the nanowires morphology were investigated.It was found that the Bi₂Se₃ nanoplates were synthesized successfully at 650 and 700?,and the size of nanoplates prepared at 700?is larger than 650?.At 700?heating temperature,the Bi₂Se₃ nanotowers and nanoplates were primary grown at 560?substrate temperature,as the temperature decrease,the nanoribbons appeared at 530?substrate temperature,while at 490?substrate temperature the mainly products are nanoribbons.In UV and PL spectra analysis,the absorbed and luminescence peak location of Bi₂Se₃ nanoplates are identical with that of Bi₂Se₃ nanowires,only different in intensity.The Cu-doped Bi₂Se₃ nanowires were prepared in 650?heating temperature by VD method based on VLS mechanism using Au/Cu catalyst.The length and density of nanowires have declined due to the addition of Cu in catalyst.The X-ray photoelectron spectroscopy?XPS?and excitation of Auger electron spectrum?XAES?of Cu in Cu-doped Bi₂Se₃nanowires were analysed,which shown Cu existed in Cu⁰ and Cu⁺11 can be considered as the gap doping and displacement doping.In UV and PL spectra analysis,the absorbed and luminescence peak location of Cu-doped Bi₂Se₃ nanowires are similar with that of Bi₂Se₃nanowires due to the little Cu-doped content.