Upper Critical Field and Flux Pinning Studies in NbN Ultra-t
发布时间：2023-12-08 19:47
过去几年中,基于超薄薄膜上的曲折纳米线在单光子检测中显示出巨大的潜力。一方面由于超薄薄膜或纳米线的超导特性,器件的性能会大大提升。另一方面,由于高温超导体在高场超导磁体应用中具有较高的Tc和Hc2,所以器件也能在高超导磁场下应用。IBS有构造高磁场磁体的潜力,未来该磁体可用于领域,例如高能粒子加速器和下一代聚变反应堆。因此,对其进行He+离子辐照作用的研究有极大的兴趣。本论文涵盖了我对薄膜和曲折纳米线的制造及其超导性能的研究工作,工作包括一下三部分:第一部分,制备了不同厚度的高质量Nb N薄膜。针对不同的场方向测量了上临界场的温度和角度依赖性。对于超薄样品,我们发现平行于表面方向的上临界场在接近Tc区域呈现上弯曲线行为,表明样品具有二维(2D)性质,这也从角度依赖性得到证实。并且我们发现随着厚度的增加,该特征逐渐减小。其温度依赖性可以通过基于各向异性Ginzburg Landau理论的模型来描述。有趣的是,在垂直于薄膜表面的场中测得的结果表明,对于超薄薄膜样品,在非常窄接近Tc...
【文章页数】：141 页
【学位级别】：博士
【文章目录】：
摘要
Abstract
CHAPTER1:Overview of superconductivity
1.1 Brief history of superconductor
1.2 London approach
1.3 Ginzburg-Landau Theory
1.3.1 G-L equations
1.3.2 Condensation energy
1.3.3 Superconducting characteristic lengths
1.3.4 Interface energy and critical fields
1.3.5 Surface superconductivity in thin films
1.4 Research motivation
CHAPTER2:Flux pinning characteristics in superconductors
2.1 Abrikosov vortex lattice
2.2 Beans’critical state model
2.3 Flux pinning forces
2.4 Elastic modulus of flux line lattice
2.5 Flux pinning models
2.5.1 The Kramer model and other models
2.6 Overview on Nb N and iron based superconductors
CHAPTER3:Fabrication and experimental techniques
3.1 DC magnetron sputtering
3.2 Pulsed laser deposition(PLD)
3.3 Micro-fabrication technology
3.3.1 Photolithography
3.3.2 Reaction ion etching(RIE)and lift-off process
3.4 Sample Characterization
3.4.1 The X-Ray Diffraction(XRD)characterization
3.4.2 The X-Ray Reflectivity(XRR)technique
3.5 Superconducting properties Measurement systems
3.5.1 Electric Measurements(PPMS)
3.5.2 Magnetic Measurements(VSM)
CHAPTER4:Study the Hc2 in Nb N thin films of different thickness and Nb Ti N meander wire
4.1 Abstract
4.2 Introduction
4.3 Sample Fabrication
4.4 Results and Discussion
4.4.1 X-ray characterization and resistive transition
4.4.2 Temperature and angular dependence of Hc2
4.4.3 Enhanced Hc2 in Nb N thick films
4.4.4 Angular dependence of magneto-resistance
4.4.5 Current voltage characteristics
4.5 Summary of the chapter
CHAPTER5:Enhancement of critical current density in He+ion irradiated Ba(Fe,Co)2As2 thin films
5.1 Abstract
5.2 Introduction
5.3 Experimental Details
5.4 Results and Discussion
5.4.1 X-ray characterization and resistive transition
5.4.2 Field dependence of critical current density
5.4.3 Flux pinning properties
5.5 Conclusion
CHAPTER6:Flux jumps and study the Jc and flux pinning properties of KCa2Fe4As4F2 single crystal
6.1 Introduction
6.2 Experimental
6.3 Results and Discussion
6.4 Summary
CHAPTER7:Summary and Future work
References
List of publications
Conference presentations
Acknowledgements
本文编号：3871039
【文章页数】：141 页
【学位级别】：博士
【文章目录】：
摘要
Abstract
CHAPTER1:Overview of superconductivity
1.1 Brief history of superconductor
1.2 London approach
1.3 Ginzburg-Landau Theory
1.3.1 G-L equations
1.3.2 Condensation energy
1.3.3 Superconducting characteristic lengths
1.3.4 Interface energy and critical fields
1.3.5 Surface superconductivity in thin films
1.4 Research motivation
CHAPTER2:Flux pinning characteristics in superconductors
2.1 Abrikosov vortex lattice
2.2 Beans’critical state model
2.3 Flux pinning forces
2.4 Elastic modulus of flux line lattice
2.5 Flux pinning models
2.5.1 The Kramer model and other models
2.6 Overview on Nb N and iron based superconductors
CHAPTER3:Fabrication and experimental techniques
3.1 DC magnetron sputtering
3.2 Pulsed laser deposition(PLD)
3.3 Micro-fabrication technology
3.3.1 Photolithography
3.3.2 Reaction ion etching(RIE)and lift-off process
3.4 Sample Characterization
3.4.1 The X-Ray Diffraction(XRD)characterization
3.4.2 The X-Ray Reflectivity(XRR)technique
3.5 Superconducting properties Measurement systems
3.5.1 Electric Measurements(PPMS)
3.5.2 Magnetic Measurements(VSM)
CHAPTER4:Study the Hc2 in Nb N thin films of different thickness and Nb Ti N meander wire
4.1 Abstract
4.2 Introduction
4.3 Sample Fabrication
4.4 Results and Discussion
4.4.1 X-ray characterization and resistive transition
4.4.2 Temperature and angular dependence of Hc2
4.4.4 Angular dependence of magneto-resistance
4.4.5 Current voltage characteristics
4.5 Summary of the chapter
CHAPTER5:Enhancement of critical current density in He+ion irradiated Ba(Fe,Co)2As2 thin films
5.1 Abstract
5.2 Introduction
5.3 Experimental Details
5.4 Results and Discussion
5.4.1 X-ray characterization and resistive transition
5.4.2 Field dependence of critical current density
5.4.3 Flux pinning properties
5.5 Conclusion
CHAPTER6:Flux jumps and study the Jc and flux pinning properties of KCa2Fe4As4F2 single crystal
6.1 Introduction
6.2 Experimental
6.3 Results and Discussion
6.4 Summary
CHAPTER7:Summary and Future work
References
List of publications
Conference presentations
Acknowledgements
本文编号：3871039
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