LIFT-OFF TECHNIQUE OF HOMOEPITAXIAL CVD DIAMOND FILMS BY DEEP IMPLANTATION AND SELECTIVE ETCHING

We report on the replication of diamond substrates and the production of thin free-standing monocrystalline diamond films by applying a ''li ft-off'' technique as suggested by Parikh et al. A diamond substrate i s first deeply implanted in order to create a damaged subsurface layer that is selectively etched after overgrowth, In this process incomple te delamination and chipping appeared to be a problem. In order to opt imize the preparation conditions for a successful lifting, we implante d diamond substrates with O+ ions of 4.5 MeV at various doses. The fil ms were subsequently overgrown with microwave plasma-assisted CVD and etched in air at elevated temperatures. With implantation doses betwee n 1 x 10(17) and 5 x 10(17) cm(-2) the CVD Iayers could be completely removed. Using optimized conditions a multiple replication with consec utive application of the lift-off technique has been demonstrated. The films were characterized by optical microscopy, X-ray diffraction and Raman spectroscopy. For the best samples, which were successfully sep arated, the Raman spectra show a sharp diamond phonon line of 2.5 cm(- 1) half-width for both the substrate and the lifted layer. To get dept h-resolved structural information, cross-sectional micro-Raman spectro scopy was applied on samples that were partially implanted and overgro wn with C-13. Polished side faces ewe access to both the predamaged re gion and the undamaged reference area. The data indicate that the impl antation damage is restricted to a thin subsurface layer with only a s mall influence on the structural quality of the overgrown film. (C) 19 97 Elsevier Science S.A.