High-resolution x-ray scattering study of platinum thin films on sapphire

Platinum films in the thickness range 20-500 Angstrom have been sputtered onto (11 (2) over bar 0) sapphire substrates at different substrate temperatures T-S. The structural properties of these films have been studied by high-resolution x-ray scattering techniques. Information about the total thickness of the film and about the surface and interface roughnesses has been determined by means of x-ray specular reflectivity measurements. The films sputtered at T-S greater than or equal to 300 degrees C have shown Laue oscillations about the Pt(lll) Bragg peak. The average thickness of coherently stacked lattice planes L-C has been compared with the total him thickness t(tot), obtained from the reflectivity measurements. The epitaxial relationship between the platinum film and the sapphire substrate has been determined using in-plane x-ray diffraction. It was demonstrated that Pt epitaxial films include two in-plane orientations related by 180 degrees rotation. Both anisotropic compression in the [1 (1) over bar 0] direction and anisotropic expansion in the [111] direction were observed for these films. A correlated variation of some structural parameters with the substrate temperature T-S was found.