Surface-activated direct bonding of diamond (100) and c-plane sapphire with high transparency for quantum applications
Tetsuya Miyatake (Fujitsu Limited)
Kenichi Kawaguchi (Fujitsu Limited)
Manabu Ohtomo (Fujitsu Limited)
Toshiki Iwai (Fujitsu Limited)
Tetsuro Ishiguro (Fujitsu Limited)
Yoshiyasu Doi (Fujitsu Limited)
Jeffrel Hermias (TU Delft - Safety and Security Science, TU Delft - QuTech Advanced Research Centre)
Salahuddin Nur (TU Delft - QuTech Advanced Research Centre, TU Delft - Quantum Circuit Architectures and Technology)
Ryoichi Ishihara (TU Delft - QuTech Advanced Research Centre, TU Delft - QID/Ishihara Lab, TU Delft - Quantum Circuit Architectures and Technology)
Shintaro Sato (Fujitsu Limited)
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Abstract
Surface-activated direct bonding of diamond (100) and c-plane sapphire substrates is investigated using Ar atom beam irradiation and high-pressure contact at RT. The success probability of bonding strongly depends on the surface properties, i.e, atomic smoothness for the micron-order area and global flatness for the entire substrate. Structural analysis reveals that transformation from sapphire to Al-rich amorphous layer is key to obtaining stable bonding. The beam irradiation time has optimal conditions for sufficiently strong bonding, and strong bonding with a shear strength of more than 14 MPa is successfully realized. Moreover, by evaluating the photoluminescence of nitrogen-vacancy centers in the diamond substrate, the bonding interface is confirmed to have high transparency in the visible wavelength region. These results indicate that the method used in this work is a promising fabrication platform for quantum modules using diamonds.
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