Research On Superconductivity Of Bi₂Te₃/FeTe Heterojunction

Superconductor is a kind of material with great application value in many fields,including medical instrumentation,electricity transportation as well as energy conservation.The research on superconducting materials mainly focuses on exploring the mechanism of superconductivity and finding ways to improve the critical temperature,both are critical for broadening the application.High temperature superconducting material is the best platform to achieve this research purpose.Cuperate superconducting materials generally have high superconducting temperature?with Tc exceeding the boiling point of liquid nitrogen?,but their internal mechanism has not been well explained until now,limiting the further optimization of transition towards room temperature.In the past decade,Iron-based superconducting materials,having some structural similarities with cuperate superconducting materials,may bring some new inspiration for the study of high temperature superconductivity,therefore,shed the light for resolving the mechanism of high temperature superconductors.Owing the simplest lattice structure for hosting superconductivity by doping,FeTe is feasible to be studied.It has been found that Bi₂Te₃/FeTe heterojunction has superconducting property recently,bringing the interface engineering an effective way for inducing superconductivity.Meanwhile,the other binary compound in this heterojunction,Bi₂Te₃,is a topological insulator,also a best candidate for realizing topological superconducting quantum states which is crucial for stable quantum computation.Therefore,this heterojunction contains rich physical meaning to be unveiled,both in the study of iron-based superconductivity and topological superconductivity.In this thesis,we epitaxially grew such heterojunctions on SrTiO₃ substrates by molecular beam epitaxial method and characterized the properties of the samples from various point of views,which includes following aspects:1.Study on epitaxial growth of high quality Bi₂Te₃/FeTe heterojunction.By using molecular beam epitaxial technique,we found a method to prepare this heterojunction with high quality,a stable superconducting reached.2.Characterization of Bi₂Te₃/FeTe heterojunction.The atomic structure and the ratio of chemical elements in the heterojunction has been studied by means of transmission electron microscope.In addition,the superconducting properties of the samples were tested by transport experiments.It is found that there is a superconducting phenomenon with a critical temperature of about 12K in the sample.3.Measure of the work functions of these two kinds of material.The work function was determined by UV-light electron spectroscopy,and the existence of charge transfer in the heterojunction was proved.The results show that there is hole doping in FeTe.