CRYSTAL-STRUCTURE OF THIN OXIDE-FILMS GROWN ON ZR-NB ALLOYS STUDIED BY RHEED

The highly surface sensitive reflection high energy electron diffracti on (RHEED) technique was used to determine the crystal structure of ox ide films grown on Zr-Nb alloys in air up to 673 K. The results show t hat the oxide films grown on Zr-2.5 wt% Nb (alpha-Zr + beta-Zr) have a mixture of nearly-cubic-tetragonal and monoclinic structures for film s of 200 nm thick or less and that the outer layers of films thicker t han 800 nm only have the monoclinic crystal structure. However, oxide films grown on Zr-20 wt% Nb (beta-Zr) have a stabilized nearly-cubic-t etragonal structure for all film thicknesses, studied here, up to 2100 nm.