TiO2 thin films for high energy density capacitors were prepared by r.f. magnetron sputtering at room temperature.Flexible PET (Polyethylene terephtalate) substrate was used to maintain the structure of the commercial film capacitors. Theeffects of deposition pressure on the crystallization and electrical properties of TiO2 films were investigated. The crystal structureof TiO2 films deposited on PET substrate at room temperature was unrelated to deposition pressure and showed an amorphousstructure unlike that of films on Si substrate. The grain size and surface roughness of films decreased with increasing depositionpressure due to the difference of mean free path. X-ray photoelectron spectroscopy (XPS) analysis revealed the formation ofchemically stable TiO2 films. The dielectric constant of TiO2 films was significantly changed with deposition pressure. TiO2films deposited at low pressure showed high dissipation factor due to the surface microstructure. The dielectric constant anddissipation factor of films deposited at 70mTorr were found to be 100~120 and 0.83 at 1kHz, respectively. The temperaturedependence of the capacitance of TiO2 films showed the properties of class I ceramic capacitors. TiO2 films deposited at10~30mTorr showed dielectric breakdown at applied voltage of 7V. However, the films of 500~300nm thickness depositedat 50 and 70mTorr showed a leakage current of ~10−8~10−9 A at 100 V.

• 박상식 | Park, Sang-Shik