Bi2Te3/FeTe异质结的超导性质研究

Research on Supeconductivity of Bi2Te3/FeTe Heterojunction

郭斌

11749029

硕士

凝聚态物理学

王干

2019-05-14

2019-06-03

哈尔滨工业大学

深圳

超导体是一种极具应用价值的材料，在医学、工业等方面被广泛应用，同时在能源、电力等领域也有着广阔的应用前景。对于超导材料的研究主要关注于探索超导产生的机理进而寻找提高超导体临界温度的方法。其中，高温超导材料是实现这一研究目的最好的平台。铜基超导材料普遍具有较高的超导温度，但其内部机理至今仍没有得到较好的解释。近些年发现的铁基超导材料与铜基超导材料在结构上存在一些相似之处，很可能为高温超导研究带来一些新的启发。其中FeTe作为一种结构最为简单的二元化合物，易于研究，引起了科研人员的广泛关注。近些年来，人们发现Bi2Te3/FeTe异质结具有超导性质，拉开了通过界面调控研究FeTe超导机制的序幕。同时，构成这一异质结的另一种材料，Bi2Te3，拥有制备拓扑超导（可用于拓扑量子比特的制备）所需要的电子表面态。因此，这一超导异质结中蕴含着丰富的物理意义，无论是针对铁基超导还是拓扑超导的研究，这一结构都可以提供独一无二的绝佳平台。本论文中，我们利用分子束外延方法，在SrTiO3衬底上外延生长了高质量的异质结，并对针对其生长工艺，电子结构以及电荷转移等可能影响超导形成的物性进行了系统表征。具体可以分为三个方面：1.高质量Bi2Te3/FeTe异质结的外延生长研究。利用分子束外延技术，通过调控衬底温度、束流大小等参量，探索得到高质量Bi2Te3/FeTe异质结的方法。2.Bi2Te3/FeTe异质结的表征。利用反射式高能电子衍射仪，透射电镜等方法研究该结构内部的原子结构排布，化学元素配比，另外通过输运实验检验样品的超导性质，发现样品中存在临界温度约为12K的超导现象。3.对材料功函数的测定。利用紫外光电子谱方法测定了两种材料的功函数，证明了电荷转移在材料中的存在。测定结果表明FeTe中存在空穴掺杂。

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.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.

FeTe Bi2Te3 异质结 超导 功函数

FeTe Bi2Te3 heterojunction superconductivity work function

中文

联合培养

南方科技大学

郭斌. Bi2Te3/FeTe异质结的超导性质研究[D]. 深圳. 哈尔滨工业大学,2019.