Magnetron sputtering[36,77] is a process by which the substrate to be coated is placed in a low-pressure chamber. The chamber is evacuated and suitable sputtering gases are introduced. The commonly used gases are oxygen and argon. A source for the TiO2 (also known as the target) is prepared by either compressing and sintering Ti powder or by using a Ti filament or bar. Magnets are placed on one side of the target. The distance between the target and the substrate is between 10 and 15 cm. A high d.c. voltage, usually in the order of a few thousand volts, is applied between the substrate and the target. A cyclical electromagnetic field (40 kHz-2.45 GHz)[36,77] is simultaneously applied to create plasma in the chamber. The Ti ions are transported from the target to the substrate under the effect of the applied potential.