Improvement of bonding strength between Au/Ti and SiO2 films by Si layer insertion

In the fabrication of broad band optical waveguide modulators, a certain technology must be used to prepare 15–20-μm-thick Au electrodes on the SiO2 surface covering the waveguides. A thin transition metal film is commonly inserted between the Au and SiO2 to improve adhesive strength. The transition metal film used in this study is Ti. Here, the SiO2 surface is precoated with Si prior to the Ti film formation, demonstrating a significant improvement in adhesive strength. The Si layer works as a barrier against oxidation of the Ti film due to the SiO2, leading to a homogenous film growth of metallic Ti.