Communication — Defect-free direct bonding for high-performance glass-on-LiNbO₃ devices

Fabrication of glass-on-LiNbO₃ structure by bonding technology is indispensable for acoustic micro/nanofluidic and photonic devices. However, direct bonding of LiNbO₃ and glass is very difficult to realize because there is an extremely large thermal expansion mismatch between these two materials. This work realized a cost-effective bonding approach without requiring intermediate layer after annealing at 150◦C via vacuum ultraviolet (VUV)/O₃ activation. A defect-free bonding interface was observed by high-resolution transmission electron microscopy (HRTEM). The LiNbO₃/glass bonded pairs exhibited excellent optical transmittance and these results overcome the interfacial barrier of glass-on-LiNbO₃ structures for high-performance devices.