Formation of self-oriented and -elongated nanopores in annealed amorphous Nb2O5 and Ta2O5 was analyzed by transmission electron microscopy. Along with their crystal growth, nanopores were spontaneously elongated in the a-axis direction perpendicular to the longitudinal b axis of the orthorhombic structures with strong anisotropy. In addition, the effect of tungsten on the nanovoid formation in annealed amorphous Nb2O5 and Ta2O5 was also studied. Additive tungsten atoms of a few atomic percent into Nb2O5 and Ta2O5 were found to make the aspect ratio of nanopores larger. Electron diffraction experiments revealed that the crystallized regions including elongated nanopores possess a variety of periodicity in the b-axis direction. This structural flexibility in the crystal growth of strong anisotropic structures seems to play an important role on the unidirectional growth of nanopores.
ASJC Scopus subject areas
- Physics and Astronomy(all)