Direct Atomic-Scale Imaging of Hydrogen and Oxygen Interstitials in Pure Niobium Using Atom-Probe Tomography and Aberration-Corrected Scanning Transmission Electron Microscopy

作者：Kim Yoon Jun; Tao Runzhe; Klie Robert F; Seidman David N^*

来源：ACS Nano, 2013, 7(1): 732-739.

DOI：10.1021/nn305029b

• Nb
• NbH
• Nb oxides
• atom-probe tomography
• aberration-corrected STEM
• annular bright-field images

Imaging the three-dimensional atomic-scale structure of complex interfaces has been the goal of many recent studies, due to its importance to technologically relevant areas. Combining atom-probe tomography and aberration-corrected scanning transmission electron microscopy (STEM), we present an atomic-scale study of ultrathin (similar to 5 nm) native oxide layers on niobium (Nb) and the formation of ordered niobium hydride phases near the oxide/Nb interface. Nb, an elemental type-II superconductor with the highest critical temperature (T-c = 9.2 K), is the preferred material for superconducting radio frequency (SRF) cavities in next-generation particle accelerators. Nb exhibits high solubilities for oxygen and hydrogen, especially within the RF-field penetration depth, which is believed to result in SRF quality factor losses. STEM imaging and electron energy-loss spectroscopy followed by ultraviolet laser-assisted local-electrode atom-probe tomography on the same needle-like sample reveals the NbO2, Nb2O5, NbO, Nb stacking sequence; annular bright-field imaging is used to visualize directly hydrogen atoms in bulk beta-NbH.

• 出版日期2013-1
• 单位西北大学