AbstractWith respect to Silicon-on-Diamond approaches as an alternative to SOI where diamond is used as the buried dielectric, we have in recent works demonstrated the feasibility of a novel approaches where the CVD diamond layer is grown on silicon using Bias Enhanced Nucleation (BEN) over large area substrates, then smoothed and assembled to successfully enable the fabrication of first prototypes of silicon-on-diamond substrates. The key novelty to those SOD substrates were that only a very thin box dielectric diamond layer is used (typically from 150 to 500nm thick), as required by the current SOI technology. However we had also observed that the silicon-diamond interface quality to be sensitive to the nature of the nucleation interface. Thus the current contribution here studies the chemical nature of various capping materials used to solve the issue of electrical defects in case of direct silicon-diamond interface and at the same time to enable the whole system to benefit from the high thermal conductivity of diamond when compared to other standard electrical insulating materials.