Realization of direct bonding of single crystal diamond and Si substrates

Diamond/Si junctions have been achieved by surface activated bonding method without any chemical and heating treatments. Bonded interfaces were obtained that were free from voids and mechanical cracks. Observations by using transmission electron microscopy indicated that an amorphous layer with a thickness of ∼20 nm across the bonded interface was formed, and no structural defects were observed at the interface. The amorphous layer of the diamond side was confirmed to be the mixture of sp2 and sp3 carbons by electron energy loss spectroscopy analyzation. The sp3/(sp2 + sp3) ratio estimated from the X-ray photoemission spectra decreased from 53.8% to 27.5%, while the relative intensity of sp2 increased from 26.8% to 72.5% after the irradiation with Ar fast beam which should be predominantly attributable to the diamond-graphite conversion.