Seminars Archive

Surface Nanostructuring by means of Ion Sputtering

Abstract
The surface morphology of metal surfaces, generated by ion sputtering, has been investigated by Scanning Tunneling Microscopy. On Cu(110) and Ag (110) normal sputtering produces a well-defined ripple structure whose wave vector rotates from <001> to <1-10> by increasing the substrate temperature. Moreover off-normal sputtering at low temperature (180K) generates ripples whose orientation depends both on ion direction and surface azimuthal orientation. These results are described by a continuum equation which includes, in addition to the surface curvature dependent erosion terms, a diffusion one that takes into account both the surface anisotropy and the Ehrlich-Schwoebel barrier at the step edges. This barrier limits the inter-layer mass transport and generates a surface instability which, depending on temperature, overcomes that due to ion erosion. On Ag (100) this effect is more evident because at low temperature, where the diffusion is negligible, the sputtering generates only ripple structures, while at 400 K the Erlich- Schwoebel barrier produces a checkerboard structure.