Scaling of Surface Roughness in Obliquely Sputtered Chromium Films

Thin chromium films were prepared by oblique sputtering, i.e. by letting deposition species impinge onto a substrate from a significantly off-normal angle. The surface structure was studied by Atomic Force Microscopy. The images indicated a non-fractal structure at short length scales. Exponents describing the scaling of the r.m.s. roughness with film thickness and lateral length scale were found to be close to unity. The results disagree with oblique ballistic deposition simulations, and a more complex behaviour is clearly present. Unstable growth of columnar features due to Schwoebel barriers for diffusing atoms at steps in the surface may be important for our films.