Abstract
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 (∼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 (Tc = 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, Nb2O 5, NbO, Nb stacking sequence; annular bright-field imaging is used to visualize directly hydrogen atoms in bulk β-NbH.
Original language | English (US) |
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Pages (from-to) | 732-739 |
Number of pages | 8 |
Journal | ACS nano |
Volume | 7 |
Issue number | 1 |
DOIs | |
State | Published - Jan 22 2013 |
Keywords
- Nb
- Nb oxides
- NbH
- aberration-corrected STEM
- annular bright-field images
- atom-probe tomography
ASJC Scopus subject areas
- General Materials Science
- General Engineering
- General Physics and Astronomy