We report the unstable surface feature in nanometer-scale of diamondlike carbon (DLC) films deposited through C-60 evaporation with simultaneous bombardment of 1.5 keV Ne+ ions. The periodical ripples, commonly appearing in postprocessing of the deposited films, form directly at 550 degreesC and 700 degreesC, which is qualitatively consistent with the theoretical model based on sputtering yield variation with surface curvature. A dramatic transition from ripple surface to mounding roughening occurs at 400 degreesC. The graphitization with increasing temperature induces the different dominant smoothening mechanisms, which is responsible for the morphological change observed. Further, the calculations of height-height correlation function show that the roughness exponents are around 0.8 at 200 degreesC and 400 degreesC, implying self-affinity of roughened surfaces. This study exhibits a potential of ion beam assisted deposition to tune DLC morphologies by controlling the deposition parameters to drive the competition between ion erosion and film deposition.