Hydrophilic direct bonding of diamond (111) substrate using treatment with H 2 SO 4 /H 2 O 2

Abstract This study addresses a mechanism by which a diamond surface cleaned with a H 2 SO 4 /H 2 O 2 mixture forms a direct bonding with an oxygen-plasma-activated SiO 2 surface. Surface characterizations revealed that the cleaning with the H 2 SO 4 /H 2 O 2 mixture at 75 °C effectively OH-terminated the diamond (111) surface without a significant increase in the surface roughness. The OH-terminated diamond and SiO 2 /Si substrates formed a C–O–Si bond by thermal dehydration reaction at 200 °C without significant loss in diamond crystallinity. It is expected that the bonding technique using H 2 SO 4 /H 2 O 2 can contribute to the integration between diamond and semiconductor substrates because the high-crystallinity diamond substrate can be directly bonded through the commonly used cleaning processes.