HIGH-RESOLUTION ELECTRON-MICROSCOPY STUDIES OF NB/AL2O3 INTERFACES

Single-crystal niobium films were grown by molecular beam epitaxy (MBE) on (0001)S, (1100)S and (1210)S sapphire substrates. Cross-sectional specimens with thickness of < 20 nm were prepared so that the Nb/Al2O3 interface could be investigated by high-resolution electron microscopy (HREM). The same unique orientation relationship is obtained for niobium films deposited on differently oriented sapphire substrates: (0001)S Verbar;(111)Nb and [2110]S Verbar;[11 0]Nb. The atomistic structure of the interface was identified by HREM. Defects at or close to the interface were analyzed. A model for the atomic arrangement at the interface will be proposed. © 1990.