Hydrophilic direct bonding of monocrystalline (111) diamond substrate onto Si wafer

An OH-terminated monocrystalline (111) diamond substrate was directly bonded onto a thermally oxidized Si substrate by hydrophilic bonding. For the hydrophilic bonding of diamond, it has been an obstacle to functionalize the surface with hydroxyl group without an increase in roughness. In the present study, the (111) diamond substrate was OH-terminated using H
₂
SO
₄
JH
₂
O
₂
mixture at a moderate temperature, and it was bonded with a thermally oxidized Si substrate irradiated by oxygen plasma. After contacting the substrates, it was annealed at 200 °C for dehydration reaction. While the edges of diamond substrate were rarely bonded, the diamond and Si substrates form direct bonding in atmospheric air without irradiation of energic particles that transforms diamond into amorphous carbon layer.