Effects of roll-to-roll sputtering conditions on the properties of flexible TiO₂ films

Flexible TiO₂ films were deposited as dielectric materials for high-energy-density capacitors on polyethylene terephthalate (PET) substrates using a roll-to-roll sputtering method. Both the growth behavior and electrical properties of the flexible TiO₂ films were dependent on the sputtering pressure and O₂/Ar gas ratio during the sputtering process. All TiO₂ films had an amorphous structure regardless of the sputtering conditions due to the low substrate temperature. Microstructural characteristics such as the surface morphology and roughness of the films degraded with an increase in the sputtering pressure and O₂ gas concentration. The TiO₂ films deposited at a low pressure showed better electrical properties than those of films deposited at a high pressure. The TiO₂ films prepared at 10 mTorr exhibited a dielectric constant of approximately 90 at 1 kHz and a leakage current density of 5 ∼ 6 × 10-7A/cm2 at 3 MV/cm.