Cluster size dependence of surface morphology after gas cluster ion bombardments

Cluster size dependence of the surface morphology of gold was investigated using a size-selected gas cluster ion irradiation system equipped with a strong permanent magnet. In addition to the cluster size effects, the incident angle dependence of surface morphology was studied. At normal incidence, a gold surface was smoothed after irradiation with any size of cluster ions. At the incident angle of 45 deg. and 60 deg., ripples with wavelength of several hundreds of nanometers were formed; however, there was no significant cluster size dependence of ripple structures. When the incident angle was increased to 70 deg. or 80 deg., the direction of the ripples became parallel to the incident angles and the cluster size dependence became remarkable