High-rate low-temperature dc pulsed magnetron sputtering of photocatalytic TiO(2)films: the effect of repetition frequency

The article reports on low-temperature high-rate sputtering of hydrophilic transparent TiO(2)thin films using dc dual magnetron (DM) sputtering in Ar + O(2)mixture on unheated glass substrates. The DM was operated in a bipolar asymmetric mode and was equipped with Ti(99.5) targets of 50 mm in diameter. The substrate surface temperature T(surf)measured by a thermostrip was less than 180 °C for all experiments. The effect of the repetition frequency f(r)was investigated in detail. It was found that the increase of f(r)from 100 to 350 kHz leads to (a) an improvement of the efficiency of the deposition process that results in a significant increase of the deposition rate a(D)of sputtered TiO(2)films and (b) a decrease of peak pulse voltage and sustaining of the magnetron discharge at higher target power densities. It was demonstrated that several hundreds nm thick hydrophilic TiO(2)films can be sputtered on unheated glass substrates at a(D) = 80 nm/min, T(surf) < 180 °C when high value of f(r) = 350 kHz was used. Properties of a thin hydrophilic TiO(2)film deposited on a polycarbonate substrate are given.