The surface morphology generated by ion sputtering on a Cu(110) crystal has
been investigated by Scanning Tunneling Microscopy (STM). A ripple structu
re is observed for all the considered values of the incident ion beam angle
theta (0 degrees < theta < 70 degrees). In particular, normal:sputtering p
roduces 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 follo
wing a scaling law lambda proportional to t(z), with z = 0.26 +/- 0.02. The
se results are described by a continuum equation which includes, in additio
n to the surface curvature dependent erosion terms, a diffusion term that t
akes into account both the surface anisotropy and the effect of an Ehrlich-
Schwoebel barrier.