Single-step microstructure patterning in titania-doped sol-gel glassy thin films with electron beams

To achieve a simplified microstructure patterning process, patterning in thin films with a single-step exposure to UV-light or E-beam process for fabrication of integrated optical waveguides and components is of great interest in optics, because the complicated structure developing stage by wet chemical or plasma etching is not required. In this paper, we describe our study on the microstructure patterning in TiO₂-doped hybrid glassy polymer thin films by irradiating with focused E-beam. An anhydrous sol-gel process based on hydrolysis and condensation of metal alkoxides with boric acid under non-hydrous conditions was applied to homogeneously incorporating TiO₂ into silica network, and transparent glassy TiO₂-doped thin films with varied TiO₂ concentrations (up to 40 mol%) were prepared by spin coating the hybrid polymer onto fused silica substrates and silicon wafers. The TiO₂-doped hybrid material showed a low OH absorption, low optical losses at the telecommunication windows (<0.40 dB/cm at 1550 nm and <0.20 dB/cm at 1310 nm respectively), good thermo-optical linearity and good thermal stability up to 200 °C. Single-step direct surface patterning in the TiO₂-doped hybrid glassy films with focused electron beams irradiation showed that tine structure with resolution at submicron level can be fabricated. As the process does not need a developing (etching) process, the profiles of the lines fabricated by the E-beam direct writing showed few distortion. The high precise patterning microstructure with submicron feature sizes in the TiO₂-doped hybrid glassy thin films may provide potentials for applications to the fabrication of optical gratings.