Control of characteristic lengths for self-organized nanostructures of amorphous carbon

We report the self-organized nanostructures of hydrogen-free amorphous carbon (a-C) with controllable characteristic length scales obtained by using ion beam assisted deposition. By selecting various temperature regimes, two kinds of nanostructure, mounds and ripples, are successfully formed. For the growth temperature of 200 0C, the fractal analysis of the surface shows that the lateral characteristic length for mounding structures increases with increasing ion energy. But for ripple structures formed in the relatively high temperature region, the ripple wavelengths are found to show a nonlinear dependence on the ion energy. Further, at certain temperatures there exist energy thresholds for stopping the formation of ripple structures. These results demonstrate that the characteristic scales of nanostructures for a-C can be significantly controlled through the tuning ion energy in a well-defined manner