A method for obtaining a smooth, single crystal diamond surface is presented, whereby a sacrificial defective layer is created by implantation and graphitized by annealing before being selectively etched. We have used O+ at 240 keV, the main process variables being the ion fluence (ranging from 3x10^15 cm^-2 to 3x10^17 cm^-2) and the final etching process (wet etch, H2 plasma and annealing in air). The substrates were characterized by atomic force microscopy, optical profilometry and white beam X-ray topography. The influence of the various process parameters on the resulting lift-off efficiency and final surface roughness is discussed. An O+ fluence of 2x10^17 cm^-2 was found to result in sub-nanometre roughness over tens of um^2.
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