Thin films TiO2 photocatalysis deposited by dual cathode magnetron sputtering
Titanium dioxide (TiO2) films were deposited by the following two different reactive magnetron sputtering systems using Ti metal targets, (1) conventional single cathode r.f. magnetron sputtering (13.56 MHz) and (2) medium frequency (50 kHz) dual cathode magnetron sputtering (DMS) with plasma emission monitoring (PEM) system. The TiO2 films deposited by the r.f. magnetron sputtering at 200 °C under total gas pressure of 0.3, 1.0 and 3.0 Pa with oxygen flow ratio (O2/O2 + Ar) of 30 % showed polycrystalline anatase structure, which exhibited UV-induced hydrophilic properties. The DMS process with PEM feedback system enable us to control the reactive sputter conditions precisely in the hysteresis "transition region" and TiO2 films with excellent UV-induced hydrophilicity (a water contact angle goes to almost 0° after 1-hour UV illumination) could be successfully obtained with high reproducibility.