Characterization of single-crystalline Nb films on sapphire by RBS/channeling technique

Abstract The crystal quality of MBE deposited Nb films on sapphire substrates was characterized with ion channeling by detecting backscattered ions and ion-induced secondary electrons. The crystal quality in the films is as good as that in a well-annealed bulk Nb crystal. The orientation relationship between Nb layer and sapphire is consistent with that reported through diffraction studies. Two-dimensional mapping of the secondary electron yield in the angular coordinate gives evidence of the excellent crystal quality in the subsurface region and the crystal symmetry of Nb (0 0 1) on sapphire (1 1 0 2) . It is demonstrated that T c in single-crystalline Nb films decreases with decreasing Nb thickness, in contrast to the case of polycrystalline films.