Transmission electron microscopy investigation of oxidation of (110)NiAl single crystal with wedge-shaped profile

• Published in: Japanese Journal of Applied Physics 2016-02, Vol.55 (2S), p.2
• Main Authors: Fedchenko, Olena, Chernov, Sergey V., Klimenkov, Michael, Protsenko, Serhiy I., Nepijko, Sergej A., Schönhense, Gerd
• Format: Article
• Language: English
• ISSN: 0021-4922; 1347-4065
• DOI: 10.7567/JJAP.55.02BC15

Low energy electron diffraction (LEED), high resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray (EDX), and electron energy loss spectroscopy (EELS) investigations of oxidation processes in (110)NiAl single crystal of wedge like shape, i.e., on the sample s areas of different thickness, were carried out. It was found that in the result of several cycles of ion etching, annealing and oxidation the upper layer of (110)NiAl is enriched with Ni. With the increase of Ni concentration from 50 to 100 at. %, the stoichiometry of the near surface area changes and the new phases of Ni3Al and Ni with Al doping are formed one after another. Up to Ni content of 75 at. % the defects concentration in the near-surface area increases and above 75 at. % it drops again. This leads to the change in orientation and azimuth direction of aluminum oxide (alumina). By varying the conditions of γ-Al2O3 epitaxial growth on (110)NiAl with (100), (110), and (111) orientations, we found that this oxide can be grown with different azimuthal directions, for example [440](111)γ-Al2O3 [002](110)NiAl and [440](111)γ-Al2O3 [022](110)NiAl.