石英衬底上超导铌金属薄膜的制备技术研究

发布时间：2018-06-15 02:27

本文选题：铌超导薄膜 + 超导转变温度　；参考：《电子科技大学》2014年硕士论文

【摘要】：高质量超导铌金属薄膜的超导转变温度(Tc)可达到9.3 K,能经受多次高低温循环而超导性能不降低,另外其还具有机械强度高、耐腐蚀等特点。因此自铌超导薄膜实现以来,就被迅速的应用于国防、医疗、能源等诸多领域。目前通常采用磁控溅射法制备铌超导薄膜,但是由于铌金属熔点高、易吸氧,在制备过程中铌膜的质量会受到多种因素的影响。因此本论文基于直流磁控溅射镀膜法在石英衬底上开展了高质量的超导铌金属薄膜的制备工艺的研究。主要研究成果如下:首先采用简单的直流磁控溅射镀膜设备在平面石英衬底上制备铌膜,并通过X射线衍射仪(XRD)、原子力显微镜(AFM)、四探针电阻测试仪、综合物性测量系统(PPMS)等分析手段来表征薄膜。研究发现制备的铌膜为体心立方结构的多晶薄膜,并沿(110)晶向择优生长。通过研究不同工艺参数(溅射气压、衬底温度、薄膜厚度、沉积速率、退火过程等)对铌膜质量的影响,发现溅射气压、衬底温度、薄膜厚度等参数均对铌膜的结晶状况、内部应力、表面形貌、电性能有显著地影响。通过参数优化,在平面石英衬底上制备出了结晶质量较好、表面光滑致密(RMS为2.88 nm)、内部应力(-0.31 GPa)较小、超导转变温度为9.07 K的铌超导薄膜。其次通过改善铌膜制备条件并结合铌膜生长规律,研究了衬底偏压对磁控溅射制备铌膜结构和性能的影响,研究发现:一定的衬底负偏压(-100 V)会促使铌膜电阻率增加,不利于提高铌膜电性能。另外还利用铌原子的“吸气”特性,通过提高溅射功率在3.5×10-4 Pa的背景真空下制备出结晶质量高、表面光滑致密(RMS为3.9 nm)、内部应力(约为-0.20 GPa)较小、超导转变温度为9.3 K的高质量铌超导薄膜。最后为制备可用于磁悬浮技术研究的球面铌超导薄膜,本论文还通过改进磁控溅射镀膜设备的结构并设计出球形衬底托盘,研究了不同运动状态下球面铌膜的厚度分布情况,并在表面光滑的实心石英球衬底上制备出附着性较好、表面电阻较低(电阻平均值为4.5?,电阻均方差为0.19)、膜厚分布较均匀的球面铌金属薄膜。
[Abstract]:The superconducting transition temperature (Tc) of the high quality superconducting niobium thin film can reach 9.3 K, which can withstand many high and low temperature cycles without decreasing the superconductivity. In addition, it also has the characteristics of high mechanical strength and corrosion resistance. Since the realization of niobium superconducting thin film, it has been applied to many fields such as national defense, medical treatment, energy and so on. At present, niobium superconducting films are prepared by magnetron sputtering, but the quality of niobium films is affected by many factors due to the high melting point of niobium metal and its easy oxygen absorption. Therefore, the preparation process of high quality superconducting niobium thin films on quartz substrate is studied based on DC magnetron sputtering. The main research results are as follows: firstly, a simple DC magnetron sputtering device is used to prepare niobium film on a planar quartz substrate, and an X-ray diffractometer (XRD), an atomic force microscope (AFM) and a four-probe resistance tester are used to prepare niobium films. Comprehensive physical property measurement system (PPMS) and other analytical means to characterize the film. It is found that the niobium film is a bulk-centered cubic polycrystalline film, which grows in a preferential direction along the crystal direction of 1 10). By studying the effect of different process parameters (sputtering pressure, substrate temperature, film thickness, deposition rate, annealing process, etc.) on the quality of niobium film, it is found that sputtering pressure, substrate temperature and film thickness all affect the crystallization of niobium film. The internal stress, surface morphology and electrical properties are significantly affected. By optimizing the parameters, niobium superconducting thin films with good crystallization quality, smooth and compact surface RMS of 2.88 nm, internal stress of -0.31 GPA and superconducting transition temperature of 9.07 K have been prepared on planar quartz substrates. Secondly, the influence of substrate bias on the structure and properties of niobium film prepared by magnetron sputtering is studied by improving the preparation conditions of niobium film and combining the growth rule of niobium film. It is found that a certain negative bias voltage of substrate can increase the resistivity of niobium film. It is unfavorable to improve the electrical properties of niobium film. In addition, by increasing the sputtering power at 3.5 脳 10 ~ (-4) Pa in a background vacuum, the niobium atoms were prepared with high crystallization quality, smooth and compact surface RMS of 3.9 nm and low internal stress (about -0.20 GPa) by using the "inspiratory" characteristics of niobium atoms. High quality niobium superconducting thin films with superconducting transition temperature of 9.3 K. Finally, in order to prepare spherical niobium superconducting films which can be used in magnetic levitation technology, the thickness distribution of spherical niobium films in different motion states is studied by improving the structure of magnetron sputtering equipment and designing a spherical substrate tray. The spherical niobium thin films with good adhesion and low surface resistance (average resistance 4.5g, resistance mean deviation 0.19g) and uniform film thickness distribution were prepared on the surface of solid quartz sphere with smooth surface.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM26

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