High-temperature direct bonding of langasite using oxygen plasma activation

A plasma-activated direct bonding method of langasite at 1000 degrees C under the pressure of 6 MPa has been achieved. The optimized plasma parameter analyzed by the infrared spectroscopy is oxygen 200 W for 45 s. According to water contact angle and atomic force microscope analysis, oxygen plasma activation can remove organic pollutants, improves surface hydrophilicity, and reduces surface roughness. A high bonding strength of 3.81 MPa is obtained by a tensile machine, and the cavity is well sealed tested by a leaking experiment. Cross-sectional transmission electron microscopy shows a defect-free and tightly bonded interface and the interlayer of the bonding interface is 0.842 nm, which implies good crystallinity. Direct bonding of langasite is of great significance to the fabrication of surface acoustic wave devices operating in high temperatures. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.