Fig. 3: Sapphire sensing chip fabrication process.

a Wet etching of sapphire, b measurement results of surface roughness of sapphire after etching using Profilometer, c roughness: Y Profile, d Roughness: X Profile, e direct bonding of sapphire

a Wet etching of sapphire, b measurement results of surface roughness of sapphire after etching using Profilometer, c roughness: Y Profile, d Roughness: X Profile, e direct bonding of sapphire