Yang Li, Liu Baiqi, Ye Zongbiao, Yang Chi, Wang Zhijun, Chen Bo, Chen Jianjun, Sha Peng, Dong Chao, Zhu Jie, Li Zhiling, Yan Rong, Ding Rui, Zhang Kun, Gou Fujun
Key Laboratory of Radiation Physics and Technology, Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu 610064, People's Republic of China.
Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, People's Republic of China.
Nanotechnology. 2021 Mar 23;32(24). doi: 10.1088/1361-6528/abeb99.
Systematic analysis of the surface morphology, crystalline phase, chemical composition and elemental distribution along depth for nitrogen-doped niobium was carried out using different methods of characterization, including Scanning Electron Microscopy (SEM), Atomic-Force Microscopy (AFM), Grazing Incidence X-ray Diffraction (GIXRD), Rutherford Backscattering Spectrometry (RBS) and layer-by-layer X-ray Photoelectron Spectroscopy (XPS) analysis. The results showed that, after nitrogen doping, the surface was covered by densely distributed trigonal precipitates with an average crystallite size of 32 ± 8 nm, in line with the calculation result (29.9 nm) of nitrogen-enriched-NbN from GIXRD, demonstrating the phase composition of trigonal precipitates. The depth analysis through RBS and XPS indicated that-NbN was dominant in the topmost 9.7 nm and extended to a depth of 575 nm, with gradually decreased content. In addition, the successive change along depth in the naturally oxidized states of niobium after nitrogen doping, was revealed. It was interesting to find that the oxygen diffusion depth could be moderately enhanced by the nitridation process. These results established the near-surface phase composition of nitrided niobium, which is of great significance in evaluating the effect of nitrogen doping and further understanding the Q improvement of the superconducting radio frequency cavities.
采用多种表征方法，包括扫描电子显微镜（SEM）、原子力显微镜（AFM）、掠入射X射线衍射（GIXRD）、卢瑟福背散射光谱（RBS）和逐层X射线光电子能谱（XPS）分析，对氮掺杂铌的表面形貌、晶相、化学成分和沿深度的元素分布进行了系统分析。结果表明，氮掺杂后，表面覆盖着密集分布的三角状析出物，平均晶粒尺寸为32±8nm，这与GIXRD计算得到的富氮NbN的结果（29.9nm）一致，证明了三角状析出物的相组成。通过RBS和XPS进行的深度分析表明，NbN在最顶层9.7nm占主导地位，并延伸至575nm深度，含量逐渐降低。此外，还揭示了氮掺杂后铌自然氧化态沿深度的连续变化。有趣的是，发现氮化过程可以适度提高氧的扩散深度。这些结果确定了氮化铌的近表面相组成，这对于评估氮掺杂的效果以及进一步理解超导射频腔的品质因数改善具有重要意义。
