Formation and Shape Transition of Nanostructures on Si(100) surfaces after MeV Sb Implantation

We have studied the formation of nanostructures on Si(100) surfaces after 1.5-bar MeV Sb implantation. Scanning Probe Microscopy has been utilized to investigate the ion implanted surfaces. We observe the formation of nanostructures after a fluence of 1x1013-bar ions/cm2. These surface structures are elliptical in shape with an eccentricity of 0.86 and their major and minor axes having dimensions of about 11.6-bar nm and 23.0-bar nm, respectively. The area of the nanostructure is 210-bar nm2at this fluence. Although the nanostructures remain of elliptical shape, their area increase with increasing fluence. However, after a fluence of 5x1014-bar ions/cm2 a transition in shape of nanostructures is observed. Nanostructures become approximately circular with an eccentricity of 0.19 and a diameter of about 30.1-bar nm. At this fluence we also observe a large increase in the area of the nanostructures to 726-bar nm2. Surface morphology and surface roughness of the ion implanted surfaces has also been discussed