The role of ion energy over the range 5 eV≤E≤20 keV in the production of the dense diamondlikesp3‐bonded phase of carbon films deposited from ion beams has been investigated. Films with a significantsp3component (≳40%), as determined by electron energy loss spectroscopy (EELS), can be formed over the wide energy region 30 eV≤E≤10 keV at room temperature. Thesp3fraction is completely suppressed only forE≤10 eV orE≥20 keV. For both cases, this suppression is associated with a sharp increase of the surface roughness, as determined by atomic force microscopy (AFM). The different nature of the mechanisms responsible for the suppression ofsp3bonding in both the low and high energy regions is discussed. ©1996 American Institute of Physics.