EPITAXIAL-GROWTH OF NIOBIUM THIN-FILMS

The properties of Nb films grown in a UHV 'metal MBE' system are described. The films were characterized by high energy electron diffraction, various x-ray diffraction techniques, as well as transport measurements. It is noted that the epitaxial relationships between (0001), (011 OVER BAR 0) and (112 OVER BAR 0) sapphire substrates and the Nb films grown on them represents a three-dimensional registry between the two lattices. Rocking curve widths, superconducting transition temperatures, and residual resistance ratios all are representative of very high quality films. An enhancement of the transition temperature by approximately 0. 3 K occurs in strained textured films grown at ambient temperature on the three orientations mentioned. Epitaxy is found to occur on the (110 OVER BAR 2) sapphire face at growth temperatures as low as ambient.