Tailoring the structural and optical properties of fabricated TiO2 thin films by O2 duty cycle in reactive gas-timing magnetron sputtering

Titanium dioxide (TiO2) thin films were deposited on silicon (100) and glass substrates via conventional reactive sputtering and reactive gas-timing (RGT) sputtering techniques. The duty cycle of supplied O2 gas determined its effect on the properties of the TiO2 films through spectroscopic ellipsometry (SE). With the best triple-layer model for SE fitting, the films' structure and optical properties were analyzed and compared. The high-resolution transmission electron microscope (HR-TEM) showed good agreement with the structure of the SE model, while the grazing-incidence X-ray diffraction (GIXRD) confirmed the crystallinity of the films. The results showed that the duty cycle was a crucial factor in the deposition rate and crystalline phase of the TiO2 films. The optical reflectance (%R) spectra were measured by a UV-VIS-NIR spectrophotometer, representing anti-reflection properties at a specific wavelength related to the duty cycle. Moreover, the omnidirectional optical transmittance (Omni-T) profiles were also determined. The results showed that the transmittances (%T) of TiO2 film near those specific wavelengths were enhanced over the bare glass substrate at a wide angle. In addition, photoelectron spectroscopy (PES) was used to confirm the chemical states and atomic compositions.