STRUCTURE OF NIOBIUM THIN-FILMS ON SAPPHIRE

The structure of Nb thin films grown by molecular beam epitaxy on sapp hire has been studied using high-resolution x-ray scattering technique s. Transverse scans of the x-ray wave vector transfer through the (110 )Nb Bragg peak show diffuse scattering with a Lorentzian-squared profi le, and satellite Bragg peaks for certain orientations of the crystal. The former feature arises from a random, two-dimensional network of N b domains, and the latter from a periodic distortion of the Nb films a t the terrace edges of the vicinal sapphire substrate.