Temperature and time evolution of ripple structure induced by ion sputtering on Cu(110)

The surface morphology generated by ion sputtering on a Cu(110) crystal has been investigated by Scanning Tunneling Microscopy (STM). A ripple structure is observed for all the considered values of the incident ion beam angle theta (0 degrees < theta < 70 degrees). In particular, normal:sputtering produces a well defined ripple structure whose wave vector rotates from (001) to (1 (1) over bar 0) by increasing the substrate temperature. Moreover, for theta = 45 degrees the ripple wavelength lambda increases in time following a scaling law lambda proportional to t(z), with z = 0.26 +/- 0.02. These results are described by a continuum equation which includes, in addition to the surface curvature dependent erosion terms, a diffusion term that takes into account both the surface anisotropy and the effect of an Ehrlich-Schwoebel barrier.