Lift-off technique of homoepitaxial CVD diamond films by deep implantation and selective etching

Abstract

We report on the replication of diamond substrates and the production of thin free-standing monocrystalline diamond films by applying a “lift-off” technique as suggested by Parikh et al. A diamond substrate is first deeply implanted in order to create a damaged subsurface layer that is selectively etched after overgrowth. In this process incomplete delamination and chipping appeared to be a problem. In order to optimize the preparation conditions for a successful lifting, we implanted diamond substrates with O + ions of 4.5 MeV at various doses. The films were subsequently overgrown with microwave plasma-assisted CVD and etched in air at elevated temperatures. With implantation doses between 1 × 10 17 and 5 × 10 17 cm −2 the CVD layers could be completely removed. Using optimized conditions a multiple replication with consecutive 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 separated, 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 depth-resolved structural information, cross-sectional micro-Raman spectroscopy was applied on samples that were partially implanted and overgrown with 13 C. Polished side faces gave access to both the predamaged region and the undamaged reference area. The data indicate that the implantation damage is restricted to a thin subsurface layer with only a small influence on the structural quality of the overgrown film.