Chemical composition and lattice relaxations at diffusion-bonded Nb/Al2O3 interfaces
1991; Elsevier BV; Volume: 37; Issue: 1-4 Linguagem: Inglês
10.1016/0304-3991(91)90023-y
ISSN1879-2723
Autores Tópico(s)Semiconductor materials and interfaces
ResumoLow-energy Nb/Al2O3 interfaces were prepared by diffusion-bonding single crystals of Nb and sapphire (S) with an orientation relationship (110)Nb|(0001)S and [001]Nb|[01⦶10]S. This orientation relationship was previously observed between Nb and Al2O3 precipitates produced by internal oxidation. Specimens with foil normals parallel to [001]Nb (orientation I) and [1⦶10]Nb (orientation II), suitable for high resolution transmission electron microscopy, were prepared from the bulk bonds. Lattice images in orientation I revealed misfit dislocations in the Nb with a stand-off distance from the interface of 2 to 3 (110)Nb lattice plane spacings. A preferred local matching of [001]Nb atomic columns with respect to the Al2O3 crystal was also observed at this interface. A detailed analysis of the interfacial contrast in orientation II, including image simulations and comparison of observed and calculated contrast, revealed the spacing between the crystals as well as the chemical composition of the interface. The Al2O3 crystal is terminated by an Al layer which contains more Al atoms than an Al layer in Al2O3. The chemical composition is explained by the local activity of O and Al in Nb at near-interface regions, which is established during cooling from the bonding temperature.
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